A Phase 1 dose escalation and expansion trial of the next-generation oral SERD camizestrant in women with ER-positive, HER2-negative advanced breast cancer: SERENA-1 monotherapy results

BACKGROUND

SERENA-1 (NCT03616587) is a Phase 1, multi-part, open-label study of camizestrant in pre- and post-menopausal women with ER+, HER2- advanced breast cancer. Parts A and B aim to determine the safety and tolerability of camizestrant monotherapy and define doses for clinical evaluation. Patients and Methods Women aged 18 years or older with metastatic or recurrent ER+, HER2- breast cancer, refractory (or intolerant) to therapy were assigned 25 mg up to 450 mg once daily (QD; escalation) or 75, 150, or 300 mg QD (expansion). Safety and tolerability, anti-tumor efficacy, pharmacokinetics, and impact on ESR1m circulating tumor (ct)DNA levels were assessed.

RESULTS

By 9 March 2021, 108 patients received camizestrant monotherapy at 25-450 mg doses. Of these, 93 (86.1%) experienced treatment-related adverse events (TRAEs), 82.4% of which were grade 1 or 2. The most common TRAEs were visual effects (56%), (sinus) bradycardia (44%), fatigue (26%), and nausea (15%). There were no TRAEs grade 3 or higher, or treatment-related serious adverse events (TRSAEs) at doses ≤150 mg. Median tmax was achieved ∼2-4 hours post-dose at all doses investigated, with an estimated half-life of 20-23 hours. Efficacy was observed at all doses investigated, including in patients with prior CDK4/6 inhibitor and/or fulvestrant treatment, with and without baseline ESR1 mutations, and with visceral disease, including liver metastases.

CONCLUSIONS

Camizestrant is a next-generation oral SERD and pure ER antagonist with a tolerable safety profile. The pharmacokinetics profile supports once-daily dosing, with evidence of pharmacodynamic and clinical efficacy in heavily pre-treated patients, regardless of ESR1m. This study established 75, 150 and 300 mg QD doses for Phase 2 testing (SERENA-2, NCT04214288 and SERENA-3, NCT04588298).

Low RNA disruption during neoadjuvant chemotherapy predicts pathologic complete response absence in patients with breast cancer

In previously reported retrospective studies, high tumor RNA disruption during neoadjuvant chemotherapy predicted for post-treatment pathologic complete response (pCR) and improved disease-free survival at definitive surgery for primary early breast cancer. The BREVITY (Breast Cancer Response Evaluation for Individualized Therapy) prospective clinical trial (NCT03524430) seeks to validate these prior findings. Here we report training set (Phase I) findings, including determination of RNA disruption index (RDI) cut points for outcome prediction in the subsequent validation set (Phase II; 454 patients). In 80 patients of the training set, maximum tumor RDI values for biopsies obtained during neoadjuvant chemotherapy were significantly higher in pCR responders than in patients without pCR post-treatment (P = .008). Moreover, maximum tumor RDI values ≤3.7 during treatment predicted for a lack of pCR at surgery (negative predictive value = 93.3%). These findings support the prospect that on-treatment tumor RNA disruption assessments may effectively predict post-surgery outcome, possibly permitting treatment optimization.

Adjuvant Endocrine Therapy in Premenopausal Breast Cancer: 12-Year Results From SOFT

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.The Suppression of Ovarian Function Trial (SOFT; ClinicalTrials.gov identifier: NCT00066690) randomly assigned premenopausal women with hormone receptor-positive breast cancer to 5 years of adjuvant tamoxifen, tamoxifen plus ovarian function suppression (OFS), or exemestane plus OFS. The primary analysis compared disease-free survival (DFS) between tamoxifen plus OFS versus tamoxifen alone; exemestane plus OFS versus tamoxifen was a secondary objective. After 8 years, SOFT reported a significant reduction in recurrence and improved overall survival (OS) with adjuvant tamoxifen plus OFS versus tamoxifen alone. Here, we report outcomes after median follow-up of 12 years. DFS remained significantly improved with tamoxifen plus OFS versus tamoxifen (hazard ratio, 0.82; 95% CI, 0.69 to 0.98) with a 12-year DFS of 71.9% with tamoxifen, 76.1% with tamoxifen plus OFS, and 79.0% with exemestane plus OFS. OS was improved with tamoxifen plus OFS versus tamoxifen (hazard ratio, 0.78; 95% CI, 0.60 to 1.01) and was 86.8% with tamoxifen, 89.0% with tamoxifen plus OFS, and 89.4% with exemestane plus OFS at 12 years. Among those who received prior chemotherapy for human epidermal growth factor receptor-2-negative tumors, OS was 78.8% with tamoxifen, 81.1% with tamoxifen plus OFS, and 84.4% with exemestane plus OFS. In conclusion, after 12 years, there remains a benefit from including OFS in adjuvant endocrine therapy, with an absolute improvement in OS more apparent with higher baseline risk of recurrence.[Media: see text].

Adjuvant Exemestane With Ovarian Suppression in Premenopausal Breast Cancer: Long-Term Follow-Up of the Combined TEXT and SOFT Trials

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.The combined analysis of SOFT-TEXT compared outcomes in 4,690 premenopausal women with estrogen/progesterone receptor-positive (ER/PgR+) early breast cancer randomly assigned to 5 years of exemestane + ovarian function suppression (OFS) versus tamoxifen + OFS. After a median follow-up of 9 years, exemestane + OFS significantly improved disease-free survival (DFS) and distant recurrence-free interval (DRFI), but not overall survival, compared with tamoxifen + OFS. We now report DFS, DRFI, and overall survival after a median follow-up of 13 years. In the intention-to-treat (ITT) population, the 12-year DFS (4.6% absolute improvement, hazard ratio [HR], 0.79; 95% CI, 0.70 to 0.90; P < .001) and DRFI (1.8% absolute improvement, HR, 0.83; 95% CI, 0.70 to 0.98; P = .03), but not overall survival (90.1% v 89.1%, HR, 0.93; 95% CI, 0.78 to 1.11), continued to be significantly improved for patients assigned exemestane + OFS over tamoxifen + OFS. Among patients with human epidermal growth factor receptor 2-negative tumors (86.0% of the ITT population), the absolute improvement in 12-year overall survival with exemestane + OFS was 2.0% (HR, 0.85; 95% CI, 0.70 to 1.04) and 3.3% in those who received chemotherapy (45.9% of the ITT population). Overall survival benefit was clinically significant in high-risk patients, eg, women age < 35 years (4.0%) and those with > 2 cm (4.5%) or grade 3 tumors (5.5%). These sustained reductions of the risk of recurrence with adjuvant exemestane + OFS, compared with tamoxifen + OFS, provide guidance for selecting patients for whom exemestane should be preferred over tamoxifen in the setting of OFS.[Media: see text].

Alpelisib (ALP) + fulvestrant (FUL) in patients (pts) with hormone receptor–positive (HR+), human epidermal growth factor receptor 2–negative (HER2−) advanced breast cancer (ABC): Biomarker (BM) analyses by next-generation sequencing (NGS) from the SOLAR-1 study

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Background: PIK3CA mutations (mut; ~40% of HR+, HER2– ABC) are linked to poor prognosis. In SOLAR-1, ALP (PI3Kα-selective inhibitor and degrader) + FUL improved progression-free survival (PFS) vs placebo (PBO) + FUL in pts with PIK3CA-mutated HR+, HER2– ABC. Here, we focus on efficacy data by gene alterations in SOLAR-1 PIK3CA-altered (alt) cohort. Methods: SOLAR-1 was a phase 3, randomized, double-blind study of ALP (or PBO) + FUL in HR+, HER2– ABC progressing on/after an aromatase inhibitor. Baseline tissue samples with enough quantity/quality (N = 398) were retrospectively tested by NGS (FoundationOne CDx 324-gene panel) and pts grouped by PIK3CA-alteration status. Clinical benefit was assessed using PFS and hazard ratio (HR) based on tumor mutational burden (TMB) and gene alteration status in the PIK3CA-alt cohort. No multiplicity adjustment was made. Results: PIK3CA-alt (ALP, n = 120; PBO, n = 117) and PI3KCA-non-alt (ALP, n = 81; PBO, n = 80) cohorts had differential gene alteration landscapes. In the PIK3CA-alt cohort, ALP + FUL clinical benefit was seen across TMB quartiles (Q1: 0 -<2.52, Q2: 2.52 -<3.78, Q3: 3.78 -<5.04, Q4: ≥ 5.04 mut/megabase). ALP + FUL had greater benefit in pts with alt vs non-alt FGFR1/ 2 (Table). ALP + FUL benefit was independent of alterations in TP53, ESR1, CCND1, MAP3K1, and ARID1A and limited in MYC- and RAD21-alt cohorts . ALP + FUL benefit was seen in pts with alt genes in the MAPK (HR [95% CI] vs PBO: alt 0.43 [0.23 - 0.80]; non-alt 0.56 [0.40 - 0.79]) and PI3K (in addition to PIK3CA; alt 0.68 [0.38 - 1.23]; non-alt 0.48 [0.34 - 0.68]) pathways, and implicated in CDK4/6i resistance (alt 0.52 [0.30 - 0.89]; non-alt 0.53 [0.37 - 0.76]). Conclusions: The unique mut profile of PIK3CA-alt tumors did not affect ALP + FUL benefit in pts with HR+, HER2– ABC. Clinical benefit was maintained regardless of alterations in most BMs, including ESR1 and genes implicated in CDK4/6i resistance, consistent with ALP targeting the PIK3CA driver oncogene. Clinical trial information: NCT#02437318; EUDRA CT#2015-000340-42. [Table: see text]

Alpelisib (ALP) + endocrine therapy (ET) in patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–), PIK3CA-mutated (mut) advanced breast cancer (ABC): Baseline biomarker analysis and progression-free survival (PFS) by duration of prior cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) therapy in the BYLieve study

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Background: ALP (PI3K-α selective inhibitor and degrader) + fulvestrant (FUL) is approved for pts with HR+, HER2– ABC and a tumor mutation in PIK3CA (̃ 40% of these pts). Primary analyses from the Phase 2 BYLieve study demonstrated efficacy and safety of ALP + ET in pts with PIK3CA-mut, HR+, HER2– ABC in the post-CDK4/6i setting. Post hoc analyses, including pts with disease progression within 6 mo of CDK4/6i + ET treatment (Tx), confirmed ALP benefit regardless of duration of prior CDK4/6i. Here we assess baseline biomarkers in circulating tumor DNA (ctDNA) by duration of prior CDK4/6i Tx and PFS in pts from BYLieve Cohorts A and B. Methods: In the BYLieve study, pts with PIK3CA-mut, HR+, HER2– ABC had CDK4/6i + aromatase inhibitor (Cohort A) or + FUL (Cohort B) as immediate prior Tx to receiving ALP + FUL and ALP + letrozole (LET), respectively. At data cutoff dates, pts had ≥ 18-mo follow-up in Cohort A and ≥ 6-mo in Cohort B. In each cohort, pts were grouped based on duration of prior CDK4/6i Tx (≤ 6 mo or >6 mo). Alterations were detected on ctDNA using next-generation sequencing (PanCancer V2 Panel). PFS was assessed in each cohort and by duration of prior CDK4/6i Tx. Results: Of 127 and 126 pts enrolled in Cohorts A and B, respectively, 98 (≤ 6-mo: 24; >6-mo: 74) and 94 (≤ 6-mo: 28; >6-mo: 66) were included in this analysis based on availability of ctDNA samples, data on duration of prior CDK4/6i, and centrally confirmed PIK3CA-mut disease. In this population, median (m) PFS (95% CI) was 8.2 mo (5.6 - 9.5) and 5.6 mo (3.7 - 7.1) in Cohorts A and B, respectively. In Cohort A, mPFS (95% CI) was 12.0 mo (5.5-non estimable) and 6.2 mo (5.4 - 8.5) in the ≤ 6-mo and >6-mo groups, respectively. The OncoPrint genomic profiles showed that pts in the ≤ 6-mo vs >6-mo group had a lower median ctDNA fraction and fewer detected gene alterations, including in genes associated with ET and/or CDK4/6i resistance, and fewer chromosomes 8/11 amplifications (linked to early relapse). In Cohort B, mPFS was 5.9 mo (3.5 - 11.0) and 5.6 mo (3.7 - 7.1) in the ≤ 6-mo and >6-mo groups, respectively. Both groups had high median ctDNA fractions and complex tumor mutation profiles reflecting more extensive treatment history. Conclusions: Lower median ctDNA fraction and lower mutational complexity observed in Cohort A ≤ 6-mo vs >6-mo group was associated with numerically longer mPFS, potentially indicating increased dependence on the mutant PI3K-α. In Cohort B, both ≤ 6-mo and >6-mo groups had high median ctDNA fractions and similar tumor mutation profiles. Additional ctDNA and tissue analyses are needed to elucidate the correlation between ALP + ET efficacy and treatment timing and baseline genomic complexity.

Baseline and longitudinal ctDNA biomarkers in GEICAM/2013-02 (PEARL) trial cohort 2 comparing palbociclib and fulvestrant (PAL + FUL) versus capecitabine (CAPE)

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Background: The randomized PEARL trial found no superiority of PAL plus endocrine therapy over CAPE in patients (pts) with metastatic HR-positive, HER2-negative breast cancer resistant to aromatase inhibitors (Martin M, Ann Oncol 2020). We investigated associations between baseline genomic landscape and on-treatment plasma ctDNA dynamics with progression free survival, in pts from cohort 2 of the trial. Methods: Plasma was collected for ctDNA analysis from -7 days to cycle 1-day 1 (C1D1) for baseline prognostic analysis and cycle 1-day 15 (C1D15) when available, and sequenced with an in-house error-corrected targeted capture panel encompassing 21 genes commonly altered in breast cancer. For predictive ctDNA dynamics analysis, a pre-specified criteria of 14 minimum days of treatment in first cycle was required and variants with VAF <0.5% in C1D1, set as limit of detection, were excluded. The circulating DNA ratio (CDR) was calculated as a weighted mean for potentially clonal mutations at C1D1. The optimal cut-off for predicting PFS was assessed by fitting a range of cut-offs, identifying the one with lower p-value on the log-rank test. Adjusted p-values, potential overestimation corrected by a shrinkage factor and bootstrapping techniques to calculate the CI95% were used in the cutpoint Cox regression model. Results: A total of 201 pts had a C1D1 sample sequenced for baseline prognostic analysis, 146 (73%) had baseline mutations identified and 55 (27%) had no mutations. 187 (93%) pts had a paired C1D15 sample for CDR calculations. Of these, 134 (72%) had baseline mutations detected, 120 of them (90%) above 0.5%, 14 (10%) had no calls, 1 pair failed sequencing. Both baseline and CDR subsets were representative of the overall study population. Pts with TP53 mutations had worse PFS in the overall population (4.4 vs 9.3 months, logrank p= 0.04), with no differences between treatments. For on-treatment ctDNA dynamic analysis, median CDR (suppression) was lower in the CAPE arm (0.07 vs 0.21, p<0.01). There was an association between optimal cut-offs predicting PFS both in CAPE (suppressed 16.6 months vs high ctDNA 4.2 months, HR 2.37, CI95% 0.96-5.83, p=0.05) and PAL + FUL arms (suppressed 15.7 months vs high ctDNA 5.5 months, HR 2.14, CI95% 0.92-5, p=0.06). More ctDNA suppression associated with likelihood of objective responses (median CDR 0.1 in objective responders vs median CDR 0.2 in progressive disease p=0.03), with no statistical significance when stratified per treatment. Conclusions: In PEARL cohort 2, TP53 mutations associated with poor outcome regardless of treatment allocation, suggesting aggressive behaviour not specifically linked to endocrine resistance. Lack of ctDNA suppression associated with worse outcome in both patient groups. Capecitabine resulted in greater ctDNA suppression at C1D15, likely reflecting faster ctDNA suppression.

Serena-1: Updated analyses from a phase 1 study (parts C/D) of the next-generation oral SERD camizestrant (AZD9833) in combination with palbociclib, in women with ER-positive, HER2-negative advanced breast cancer

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Background: SERENA-1 (NCT03616587) is a Phase 1, multi-part, open-label study of camizestrant in women with ER+, HER2− advanced breast cancer (ABC). Parts A/B (escalation/expansion) assessed camizestrant monotherapy and have been presented previously. Parts C/D examine camizestrant in combination with palbociclib; here we present mature data from camizestrant 75 mg in combination with palbociclib; 75 mg being the camizestrant dose currently under investigation in the Phase 3 studies SERENA-4 (NCT04711252) and SERENA-6 (NCT04964934). Methods: The primary objective was to determine the safety and tolerability of camizestrant once daily (QD) with palbociclib. Secondary objectives included anti-tumor response and pharmacokinetics (PK). Prior treatment with < 2 lines of chemotherapy in the advanced setting was permitted. There was no limit on the number of lines of prior endocrine treatment in the advanced setting; prior treatment with CDK4/6 inhibitors and fulvestrant (F) was permitted. Results: As of 9 September 2021, 25 patients had received camizestrant 75 mg QD in combination with palbociclib. Tolerability of the combination of camizestrant 75 mg and palbociclib was consistent with that of each drug individually. No patient required camizestrant dose interruption/reduction/discontinuation due to a camizestrant-related adverse event (AE); moreover, none experienced a Grade ≥3 camizestrant-related AE. All camizestrant-related heart rate reductions were Grade 1 (asymptomatic). All camizestrant-related visual effects were Grade 1 (mild), apart from one patient who experienced transient Grade 2 (moderate) visual effects that resolved to Grade 1 without dose modification. Camizestrant-related gastrointestinal disorders were all Grade 1, except one instance of Grade 2 nausea lasting one day. PK data for camizestrant 75 mg QD and palbociclib combined were broadly consistent with camizestrant as monotherapy and published palbociclib steady-state PK data, further supporting the use of camizestrant 75 mg QD (Phase 3 dose) in combination with the approved palbociclib doses. In these heavily pre-treated patients (48% prior chemotherapy, 80% prior CDK4/6i, 68% prior F; all in advanced disease setting) and of whom 60% had visceral metastases, the clinical benefit rate at 24 weeks was 7/25 (28%). Conclusions: The PK and safety profile of camizestrant 75 mg QD in combination with palbociclib is favorable in this mature Phase 1 dataset. Despite extensive pre-treatment - including chemotherapies, CDK4/6i, and F - camizestrant 75 mg QD in combination with palbociclib exhibits encouraging clinical activity. The results from the ongoing Phase 3 studies, SERENA-4 and SERENA-6, will further elucidate the role of this combination in the treatment of patients with HR+/HER2− ABC. Clinical trial information: NCT03616587.

Functional Mapping of AKT Signaling and Biomarkers of Response from the FAIRLANE Trial of Neoadjuvant Ipatasertib plus Paclitaxel for Triple-Negative Breast Cancer

PURPOSE

Despite extensive genomic and transcriptomic profiling, it remains unknown how signaling pathways are differentially activated and how tumors are differentially sensitized to certain perturbations. Here, we aim to characterize AKT signaling activity and its association with other genomic or IHC-based PI3K/AKT pathway biomarkers as well as the clinical activity of ipatasertib (AKT inhibitor) in the FAIRLANE trial.

EXPERIMENTAL DESIGN

In FAIRLANE, 151 patients with early triple-negative breast cancer (TNBC) were randomized 1:1 to receive paclitaxel with ipatasertib or placebo for 12 weeks prior to surgery. Adding ipatasertib did not increase pathologic complete response rate and numerically improved overall response rate by MRI. We used reverse-phase protein microarrays (RPPA) to examine the total level and/or phosphorylation states of over 100 proteins in various signaling or cell processes including PI3K/AKT and mTOR signaling. One hundred and twenty-five baseline and 127 on-treatment samples were evaluable by RPPA, with 110 paired samples at both time points.

RESULTS

Tumors with genomic/protein alterations in PIK3CA/AKT1/PTEN were associated with higher levels of AKT phosphorylation. In addition, phosphorylated AKT (pAKT) levels exhibited a significant association with enriched clinical benefit of ipatasertib, and identified patients who received benefit in the absence of PIK3CA/AKT1/PTEN alterations. Ipatasertib treatment led to a downregulation of AKT/mTORC1 signaling, which was more pronounced among the tumors with PIK3CA/AKT1/PTEN alterations or among the responders to the treatment.

CONCLUSIONS

We showed that the high baseline pAKT levels are associated with the alterations of PI3K/AKT pathway components and enriched benefit of ipatasertib in TNBC.

Pathologic complete response (pCR) to neoadjuvant treatment with or without atezolizumab in triple negative, early high-risk and locally advanced breast cancer. NeoTRIP Michelangelo randomized study

BACKGROUND

High-risk triple negative breast cancers (TNBC) are characterized by poor prognosis, rapid progression to metastatic stage and onset of resistance to chemotherapy, thus representing an area in need of new therapeutic approaches. PD-L1 expression is an adaptive mechanism of tumour resistance to tumour infiltrating lymphocytes, which in turn are needed for response to chemotherapy. Overall, available data support the concept that blockade of PD-L1/PD-1 check-point may improve efficacy of classical chemotherapy.

PATIENTS AND METHODS

Two-hundred-eighty patients with TNBC were enrolled in this multicentre study (NCT002620280) and randomized to neoadjuvant carboplatin AUC 2 and nab-paclitaxel 125 mg/m² iv on days 1 and 8, without (N = 142) or with (N = 138) atezolizumab 1200 mg iv on day 1. Both regimens were given q3 weeks for 8 cycles before surgery and 4 cycles of an adjuvant anthracycline regimen. The primary aim of the study is to compare event-free survival, an important secondary aim was the rate of pathological complete remission (pCR defined as absence of invasive cells in breast and lymph nodes). The primary population for all efficacy endpoints is the intention-to-treat population.

RESULTS

The intention-to-treat analysis revealed that pCR rate after treatment with atezolizumab (48.6%) did not reach statistical significance compared to no atezolizumab [44.4%: odds ratio (OR) 1.18; 95% CI 0.74-1.89; P = 0.48]. Treatment-related adverse events were similar with either regimen except for a significantly higher overall incidence of serious adverse events and liver transaminases abnormalities with atezolizumab.

CONCLUSIONS

The addition of atezolizumab to nab-paclitaxel and carboplatin did not significantly increase the rate of pCR in women with TNBC. In multivariate analysis the presence of PD-L1 expression was the most significant factor influencing rate of pCR (OR 2.08). Continuing follow up for the event-free survival is ongoing, and molecular studies are under way.

Abstract GS2-05: Randomized comparison of adjuvant aromatase inhibitor exemestane (E) plus ovarian function suppression (OFS) vs tamoxifen (T) plus OFS in premenopausal women with hormone receptor-positive (HR+) early breast cancer (BC): update of the combined TEXT and SOFT trials

Background The updated combined SOFT+TEXT analysis, after 9 years median follow-up (MFU), revealed that adjuvant E+OFS vs T+OFS significantly improved disease-free survival (DFS) and distant recurrence-free interval (DRFI) but not overall survival (OS) in premenopausal women with HR+ early BC (Francis et al NEJM 2018). Given the high rate of OS in both arms and the long-term risk of relapse in HR+ BC, continued follow-up is key to assessing treatment benefit. We report a planned update analysis including OS with database lock of May 2021, after 13 years MFU.. Methods TEXT and SOFT enrolled premenopausal women with HR+ early BC from November 2003 to April 2011 (2660 in TEXT, 3047 in SOFT intention-to-treat (ITT) populations). TEXT randomized women within 12 weeks of surgery to 5 years E+OFS vs T+OFS; chemotherapy (CT) was optional and concurrent with OFS. SOFT randomized women to 5 years E+OFS vs T+OFS vs T alone, within 12 weeks of surgery if no CT planned, or within 8 months of completing (neo)adjuvant CT. Both trials were stratified by CT use. For the combined analysis of E+OFS vs T+OFS, the primary endpoint was DFS defined as invasive local, regional, distant recurrence, contralateral BC, second malignancy, death. Secondary endpoints included invasive breast cancer-free interval (BCFI), DRFI and OS.. Results: At database lock there were 953 DFS events and 473 deaths among 4690 pts assigned to T+OFS or E+OFS. In the ITT population, DFS, BCFI and DRFI outcomes for pts assigned E+OFS (n=2346) continued to be significantly improved over T+OFS (n=2344). 12-yr DFS was 80.5% vs. 75.9% (4.6% absolute improvement; HR 0.79 95% CI 0.70-0.90), 12-yr BCFI was improved by 4.1% and 12-yr DRFI by 1.8%. At 12 years OS was excellent in both groups, 90.1% in pts assigned E+OFS vs 89.1% in pts assigned T+OFS (HR 0.93; 95% CI, 0.78-1.11). There was heterogeneity of relative treatment effect according to HER2 status. When enrollment commenced, anti-HER2 adjuvant therapy was not standard; 53% of 583 pts with HER2+ tumors received HER2-targeted therapy. Below are Kaplan-Meier 12-yr estimates for patients with HER2 negative tumors by trial and chemotherapy stratum and for those with high-grade tumours, as an example of high-risk feature (Table). There is an emerging OS benefit for E+OFS vs T+OFS in pts with HER2 negative tumors who received chemotherapy in both trials.In pts with HER2-negative tumors, clinically-relevant outcome benefits were also seen in other high-risk subgroups: 12-yr DFS and OS were improved by 7.4% and 2.7%, respectively, in pts with pN1a disease, and by 10.6% and 4.5%, respectively, in those with tumors &gt;2cm.

Conclusions After 13 years MFU, adjuvant E+OFS, as compared with T+OFS, shows a sustained reduction in the risk of recurrence, more consistent in HER2 negative patients and in those with high-risk disease features, e.g., indication for adjuvant chemotherapy and G3 tumors. Oncologists may use this information to discuss potential benefits of E+OFS with individual patients. Follow-up continues for 5 additional years.

Chemotherapy HER2-negativeSOFTT+OFS (n=424)E+OFS (n=411)Absolute difference12-yr DFS67.4%74.1%6.7%12-yr OS81.1%84.4%3.3%TEXTT+OFS (n=656)E+OFS (n=661)Absolute difference12-yr DFS71.0%78.4%7.4%12-yr OS83.5%86.8%3.3%No chemotherapy HER2-negativeSOFTT+OFS (n=445)E+OFS (n=447)Absolute difference12-yr DFS82.9%88.2%5.3%12-yr OS96.1%96.9%0.9%TEXTT+OFS (n=499)E+OFS (n=492)Absolute difference12-yr DFS80.2%86.7%6.5%12-yr OS95.9%96.2%0.2%G3 HER2-negativeT+OFS (n=423)E+OFS (n=405)Absolute difference12-yr DFS62.7%73.0%10.3%12-yr OS78.1%83.6%5.5%

Citation Format: Meredith M Regan, Barbara A Walley, Gini F Fleming, Prudence A Francis, Marco A Colleoni, István Láng, Henry L Gómez, Carlo A Tondini, Harold J Burstein, Matthew P Goetz, Eva M Ciruelos, Vered Stearns, Hervé R Bonnefoi, Silvana Martino, Charles E Geyer, Jr, Claudio Chini, Alessandro M Minisini, Simon Spazzapan, Thomas Ruhstaller, Eric P Winer, Barbara Ruepp, Sherene Loi, Alan S Coates, Aron Goldhirsch, Richard D Gelber, Olivia Pagani. Randomized comparison of adjuvant aromatase inhibitor exemestane (E) plus ovarian function suppression (OFS) vs tamoxifen (T) plus OFS in premenopausal women with hormone receptor-positive (HR+) early breast cancer (BC): update of the combined TEXT and SOFT trials [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS2-05.

Abstract P5-13-03: Alpelisib + endocrine therapy (ET) in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-), PIK3CA-mutated advanced breast cancer (ABC) previously treated with cyclin-dependent kinase 4/6 inhibitor (CDK4/6i): Biomarker analyses from the Phase II BYLieve study

Introduction: Alpelisib (ALP, a PI3Kα inhibitor and degrader) + ET has demonstrated efficacy in patients (pts) with HR+, HER2-, PIK3CA-mutated ABC progressing on/after CDK4/6i + ET in the ongoing Phase II BYLieve study (NCT03056755). The primary endpoint, in pts with centrally confirmed PIK3CA mutation in tumor tissue (modified full analysis set [mFAS]), was met in Cohorts A (ALP + fulvestrant [FUL]) and B (ALP + letrozole [LET]) with 50.4% (95% CI, 41.2%-59.6%) of 121 pts and 46.1% (36.8%-55.6%) of 115 pts alive and without disease progression at 6 mo, respectively. Activating PIK3CA mutations, occurring in ~40% of tumors, confer worse prognosis in the advanced setting. Here, we assess the correlation between progression-free survival (PFS) and other baseline biomarkers among pts in BYLieve Cohorts A and B. Methods: Enrolled pre-/postmenopausal women with HR+, HER2-, PIK3CA-mutated ABC received CDK4/6i + aromatase inhibitor (Cohort A) or FUL (Cohort B), as immediate prior treatment (Tx). Pts received ALP 300 mg PO QD + FUL 500 mg IM Q28D and C1D15 (Cohort A) or ALP 300 mg PO QD + LET 2.5 mg PO QD (Cohort B) as study Tx. This exploratory analysis of baseline biomarkers identified gene alterations using an error-connected sequencing ctDNA assay (Novartis PanCancer gene-panel) in plasma samples from pts with a centrally confirmed PIK3CA mutation in tumor tissue from Cohorts A and B. PFS was estimated using the Kaplan-Meier method in subgroups of pts based on high (≥10%) or low (&lt;10%) ctDNA fraction, high (≥10) or low (&lt;10) tumor mutation burden (TMB), and amplification (amp) status of chromosomes (chr) 8 or 11 amplicons (frequently observed in breast cancer and usually associated with early relapse). Results: In Cohorts A and B, 102 of 127 enrolled pts and 97 of the 126 enrolled pts were included in this analysis, respectively. In this analysis, median PFS (mPFS) was 7.3 mo in Cohort A and 5.7 mo in Cohort B, consistent with observations in the mFAS (Table 1). Pts with a low ctDNA fraction or TMB at baseline had longer mPFS than pts with high ctDNA fraction or TMB (Table 1). In addition to PIK3CA alterations observed in 73% of tumors from pts in Cohorts A and B, the most frequently altered genes in the studied population were ESR1 (27% and 28%) and TP53 (25% and 26%) in Cohorts A and B, respectively. Across both cohorts, pts whose tumors had loss of function alterations in genes known to mediate resistance to CDK4/6i (PTEN, RB1, CHD4, FAT1, NF1, ATM, CDKN2A-C) derived clinical benefit (partial response or stable disease) from ALP + ET. Amp of known amplicons on chr 8 (eg, FGFR1, TACC1) or 11 (eg, CCND1, FGF3, FGF4) were observed in 5%-8% of pts in Cohort A and 8%-11% of pts in Cohort B. Pts whose tumors had no gene amp on chr 8 and/or 11 had longer mPFS than pts whose tumors had an amp (Table 1). Similar results were observed when analyzing chr 8 (6.33 mo vs 4.92 mo) and chr 11 (6.33 mo vs 4.63 mo) separately in pts from Cohorts A plus B. Conclusion: In pts with HR+, HER2-, PIK3CA-mutated ABC, ALP was effective in the post-CDK4/6i setting regardless of ET partner and tumor genomic profile (including in presence of alterations in genes associated with CDK4/6i resistance). The absence of cross-resistance may allow pts with PIK3CA-mutated disease to benefit from ALP after disease progression on/after CDK4/6i.

Table 1.mPFS in pts from BYLieve Cohorts A and B based on baseline biomarker statusCohort A (ALP + FUL)Cohort B (ALP + LET)nmPFS, mo (95% CI) nmPFS, mo (95% CI)Overall (mFASa)1,21217.3 (5.6-8.3)1155.7 (4.5-7.2)Patients with available plasma sample for the biomarker analysisb1027.37 (5.60-8.67)975.70 (3.77-7.33)ctDNA fractionHigh (≥10%)655.60 (4.00-7.37)685.43 (3.70-7.20)Low (&lt;10%)37NE297.33 (5.83-11.00)TMBHigh (≥10)103.85 (0.47-8.33)154.60 (1.67-5.73)Low (&lt;10)716.13 (5.43-9.60)645.63 (3.73-7.50)Chr 8 or 11 amplificationWith174.23 (1.70-6.13)213.77 (1.93-7.37)Without858.40 (5.70-9.60)766.00 (5.20-7.53)Chr, chromosome; ctDNA, circulating tumor DNA; NE, not estimable; mPFS, median progression-free survival; TMB, tumor mutation burden. aPatients who received at least 1 dose of study treatment and had centrally confirmed PIK3CA mutation by a Novartis-designated laboratory were included in the mFAS. bOnly includes patients with centrally confirmed PIK3CA mutation in tumor tissue. 1. Rugo HS, et al. Lancet Oncol. 2021;22(4):489-498; 2. Rugo HS, et al. SABCS 2020. Poster PD2-07.

Citation Format: Dejan Juric, Nicholas Turner, Aleix Prat, Stephen Chia, Eva M Ciruelos, Manuel Ruiz-Borrego, Pamela Drullinsky, Florence Lerebours, Thomas Bachelot, O. Alejandro Balbin, Mukta Joshi, Estelle Roux, Christina H Arce, Murat Akdere, Hope S Rugo. Alpelisib + endocrine therapy (ET) in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-), PIK3CA-mutated advanced breast cancer (ABC) previously treated with cyclin-dependent kinase 4/6 inhibitor (CDK4/6i): Biomarker analyses from the Phase II BYLieve study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-03.

Abstract P1-18-08: Effect of duration of prior cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) therapy (≤6 mo or &gt;6 mo) on alpelisib benefit in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-), PIK3CA-mutated advanced breast cancer (ABC) from BYLieve

Introduction: PIK3CA (encoding phosphatidylinositol 3-kinase alpha [PI3Kα]) is a driver oncogene mutated (mut) in ~40% of HR+, HER2- ABCs, leading to endocrine therapy (ET) resistance and poor prognosis. Alpelisib (ALP) is the first oral α-selective PI3K inhibitor and degrader approved in this patient (pt) population. Primary analyses of Cohorts A and B from BYLieve, an ongoing Phase II noncomparative study, demonstrated efficacy and a consistent safety profile of ALP + ET (fulvestrant [FUL] or letrozole [LET]) in pts with PIK3CA-mut, HR+, HER2- ABC in the post CDK4/6i setting. Post hoc analyses of ALP benefit in pts with centrally confirmed PIK3CA mut, based on median duration of prior CDK4/6i, supported the efficacy of ALP + ET in CDK4/6i-resistant, HR+, HER2- ABC. Here we assessed whether those who achieved a short duration of disease control (6-month [mo] cutoff), with prior CDK4/6i + ET received clinical benefit with ALP + ET. Methods: In Cohorts A and B, pts with PIK3CA-mut, HR+, HER2- ABC had received CDK4/6i + aromatase inhibitor (AI) or FUL, respectively, as immediate prior therapy (majority in first line). Pts in Cohort A received ALP 300 mg PO QD + FUL 500 mg IM Q28D + C1D15; pts in Cohort B received ALP 300 mg PO QD + LET 2.5 mg PO QD. Within each cohort, pts were divided based on duration of prior CDK4/6i therapy (≤6 mo or &gt;6 mo), and the association of progression-free survival (PFS) with this covariate was analyzed using a stratified log-rank test and Cox Proportional Hazards model. A 6-mo cutoff was selected based on the ESO-ESMO ABC5 cutoff for primary ET resistance, as current guidelines do not specify cutoffs for CDK4/6i resistance. This analysis is based on the PFS endpoint and included pts for whom duration of prior CDK4/6i therapy was known. Results: Of the 121 pts in Cohort A with centrally confirmed PIK3CA-mut disease (modified full analysis set, mFAS), 120 had duration of prior CDK4/6i available; 26 had CDK4/6i for ≤6 mo and 94 for &gt;6 mo, with similar demographics/disease characteristics between subgroups. The hazard ratio (HR) of median PFS (mPFS) between the ≤6-mo group and &gt;6-mo group was 0.50 (95% confidence interval [CI], 0.27-0.94), indicating a lower risk of progression in the ≤6-mo group, with mPFS 10.0 mo (95% CI, 5.55-not estimable) and 6.0 mo (95% CI, 5.16-8.31), respectively. Grade ≥3 adverse events (AEs) were experienced by 67.5% (n=85) of all pts (safety set) in Cohort A and by 76.9% (n=20)/65.0% (n=65) in the ≤6-mo/&gt;6-mo subgroups, respectively. Of the 115 pts in Cohort B with centrally confirmed PIK3CA-mut disease (mFAS), 113 had duration of prior CDK4/6i available; 31 had CDK4/6i for ≤6 mo and 82 for &gt;6 mo, with similar demographics/disease characteristics between subgroups. The HR of mPFS between the ≤6-mo and &gt;6-mo groups was 0.76 (95% CI, 0.47-1.23), with the wide CI indicating no difference in risk of progression between subgroups, and mPFS was 5.9 mo (95% CI, 3.55-10.97) and 5.6 mo (95% CI, 3.68-7.10), respectively. Grade ≥3 AEs were experienced by 69.9% (n=86) of all pts (safety set) in Cohort B and by 63.6% (n=21)/72.2% (n=65) in the ≤6-mo/&gt;6-mo subgroups, respectively. Conclusions: This demonstrates that pts with PIK3CA-mut, HR+, HER2- ABC who achieved ≤6-mo duration of disease control with prior CDK4/6i had a numerically longer PFS in Cohort A, and almost the same clinical efficacy in Cohort B, to ALP + ET vs pts with &gt;6-mo duration of disease control, with a comparable safety profile. This confirms targeting PI3Kα with ALP provides clinical benefit in pts with CDK4/6i-resistant ABC, including early progressors, and supports consideration of ALP + ET as an immediate next-line option in this setting, possibly delaying chemotherapy.

Citation Format: Stephen Chia, Eva M Ciruelos, Hope S Rugo, Florence Lerebours, Manuel Ruiz-Borrego, Pamela Drullinsky, Aleix Prat, Thomas Bachelot, Nicholas Turner, Ennan Gu, Christina Arce, Murat Akdere, Dejan Juric. Effect of duration of prior cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) therapy (≤6 mo or &gt;6 mo) on alpelisib benefit in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-), PIK3CA-mutated advanced breast cancer (ABC) from BYLieve [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-18-08.

Abstract PD15-01: Impact of ESR1 mutations on endocrine therapy (ET) plus alpelisib benefit in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-), PIK3CA-mutated, advanced breast cancer (ABC) who progressed on or after prior cyclin-dependent kinase inhibitor (CDK4/6i) therapy in the BYLieve trial

Introduction: Endocrine-based therapy is the standard of care for patients (pts) with HR+ ABC. Acquired ESR1 mutations (mut) have been reported in up to 56% of pts with HR+ ABC progressing after prior treatment with ET, and aromatase inhibitors (AIs) in particular. Alpelisib (ALP) is an α-selective PI3K inhibitor and degrader approved in combination with fulvestrant (FUL) for the treatment of HR+, HER2-, PIK3CA-mut ABC. The primary analysis of Cohorts A and B of the Phase II BYLieve trial demonstrated the safety and efficacy of ALP + ET in the post-CDK4/6i setting. We assessed the association between progression-free survival (PFS) and baseline ESR1 mut among pts in Cohorts A and B of the BYLieve trial. Methods: Cohorts A and B of the BYLieve trial included pre-/postmenopausal women with HR+, HER2-, PIK3CA-mut ABC who received CDK4/6i + AI (Cohort A) or CDK4/6i + FUL (Cohort B) as immediate prior therapy. Pts in Cohort B may have also received prior AI therapy. Pts received ALP 300 mg PO QD + FUL 500 mg IM Q28D and C1D15 (Cohort A) or ALP 300 mg PO QD + LET 2.5 mg PO QD (Cohort B). ESR1 mut was analyzed as an exploratory endpoint, using an error-corrected sequencing ctDNA assay (Novartis PanCancer gene-panel), in baseline plasma samples from pts with centrally confirmed PIK3CA mut in tumor tissue from Cohorts A and B. PFS by mut status was estimated using the Kaplan-Meier method. P values provided are nominal. No multiplicity adjustments were made, therefore, statistical interpretation should be made with caution. Results: 127 pts with ≥6 mo follow-up (median follow-up: 11.7 mo) were enrolled in Cohort A as of the 17 December 2019 data cut-off and 126 pts with ≥6 mo follow-up (median follow-up: 15.0 mo) were enrolled in Cohort B as of the 14 August 2020 data cut-off. 103 (81.7%) pts in Cohort B progressed on prior AI therapy (adjuvant/metastatic setting). 102 pts from Cohort A and 97 pts from Cohort B had available plasma samples and were included in this analysis. Similar outcomes were observed in this analysis and in the overall population (Table 1). At baseline, 26% (27/102) of pts in Cohort A and 26% (25/97) of pts in Cohort B had ESR1 mut detected. In Cohort A (ALP + FUL), a numerically lower PFS was observed in pts with ESR1-mut disease, but the wide confidence interval (CI) suggests no difference in risk of progression between those with and without ESR1 mut. In Cohort B (ALP + LET), pts with ESR1-mut disease had a shorter PFS compared with those without ESR1-mut disease. A possible limitation is that baseline characteristics of these subgroups may not be balanced.

Conclusion: Similar proportion of pts had ESR1-mut disease at baseline in both cohorts. All pts in Cohort A progressed on prior CDK4/6i + AI and most pts enrolled in Cohort B also progressed on prior AI therapy. This analysis suggests that pts with ESR1 mut tend to have lower PFS than those without a mut, and that ALP + LET might be less effective in pts with ESR1 mut. This adds to prior data that ESR1 mut reduce the efficacy of AI-based combination therapy. In pts with ESR1 mut detected after prior CDK4/6i therapy, ALP + FUL (the approved combination for PIK3CA-mut ABC) warrants consideration as an alternative treatment option. Studies of ALP in combination with new oral, selective estrogen-receptor degraders are also ongoing.

Table 1.Median PFS in BYLieve Cohorts A and B.Cohort A (ALP + FUL)Cohort B (ALP + LET)Overall (mFASa), N1,2121115mPFS, months (95% CI)7.3 (5.6-8.3)5.7 (4.5, 7.2)Patients with available plasma samples for ESR1-mutation testing,b N10297mPFS, months (95% CI)7.37 (5.60-8.67)5.70 (3.77-7.33)With ESR1 mutation (n=27)With ESR1 mutation (n=25) Without ESR1 mutation (n=72)mPFS, months (95% CI)5.55 (3.75-8.54)8.28 (5.45-9.46)4.57 (3.06-5.65)7.03 (4.50-8.31)Hazard ratio (95% CI)0.76 (0.44-1.33)0.55 (0.32-0.92)P value (nominal)0.30.02ALP, alpelisib; FUL, fulvestrant; LET, letrozole; mFAS, modified full analysis set; mPFS, median progression-free survival. . aPatients who received at least 1 dose of study treatment and had centrally confirmed PIK3CA mutation by a Novartis-designated laboratory were included in the mFAS. bOnly includes patients with centrally confirmed PIK3CA mutation in tumor tissue.1. Rugo HS, et al. Lancet Oncol. 2021;22(4):489-498; 2. Rugo HS, et al. SABCS 2020. Poster PD2-07.

Citation Format: Nick Turner, Hope S Rugo, Eva M Ciruelos, Manuel Ruiz-Borrego, Pamela Drullinsky, Florence Lerebours, Aleix Prat, Thomas Bachelot, Stephen Chia, Alejandro Balbin, Mukta Joshi, Estelle Roux, Christina H Arce, Murat Akdere, Dejan Juric. Impact of ESR1 mutations on endocrine therapy (ET) plus alpelisib benefit in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-), PIK3CA-mutated, advanced breast cancer (ABC) who progressed on or after prior cyclin-dependent kinase inhibitor (CDK4/6i) therapy in the BYLieve trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD15-01.

Genomic and Transcriptomic Analyses of Breast Cancer Primaries and Matched Metastases in AURORA, the Breast International Group (BIG) Molecular Screening Initiative

AURORA aims to study the processes of relapse in metastatic breast cancer (MBC) by performing multi-omics profiling on paired primary tumors and early-course metastases. Among 381 patients (primary tumor and metastasis pairs: 252 targeted gene sequencing, 152 RNA sequencing, 67 single nucleotide polymorphism arrays), we found a driver role for GATA1 and MEN1 somatic mutations. Metastases were enriched in ESR1, PTEN, CDH1, PIK3CA, and RB1 mutations; MDM4 and MYC amplifications; and ARID1A deletions. An increase in clonality was observed in driver genes such as ERBB2 and RB1. Intrinsic subtype switching occurred in 36% of cases. Luminal A/B to HER2-enriched switching was associated with TP53 and/or PIK3CA mutations. Metastases had lower immune score and increased immune-permissive cells. High tumor mutational burden correlated to shorter time to relapse in HR+/HER2- cancers. ESCAT tier I/II alterations were detected in 51% of patients and matched therapy was used in 7%. Integration of multi-omics analyses in clinical practice could affect treatment strategies in MBC. SIGNIFICANCE: The AURORA program, through the genomic and transcriptomic analyses of matched primary and metastatic samples from 381 patients with breast cancer, coupled with prospectively collected clinical data, identified genomic alterations enriched in metastases and prognostic biomarkers. ESCAT tier I/II alterations were detected in more than half of the patients.This article is highlighted in the In This Issue feature, p. 2659.

CCNE1 mRNA and cyclin E1 protein expression as predictive biomarkers for efficacy of palbociclib plus fulvestrant versus capecitabine in the phase III PEARL study

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Background: The randomized PEARL trial found no superiority of palbociclib plus endocrine therapy over capecitabine in patients (pts) with metastatic HR-positive, HER2-negative breast cancer resistant to prior aromatase inhibitors (Martin M, Ann Oncol 2020). Gene expression analysis showed high CCNE1 mRNA ( CCNE1) conferring relative resistance to palbociclib in the PALOMA-3 trial (Turner N, JCO 2019), but further validation is needed. Cyclin E1 protein (cyclin E1) expression in this context has not been studied in randomized trials. We explored CCNE1 and cyclin E1 as predictive biomarkers in tumor samples from the PEARL study. Methods: Formalin-fixed paraffin-embeded tumor samples were retrieved from pts enrolled in PEARL cohort 2 (palbociclib (PAL) + fulvestrant (FUL) vs capecitabine (CAPE)). We measured CCNE1 using the HTG EdgeSeq Oncology Biomarker Panel (HTG Molecular Diagnostics). Cyclin E1 immunohistochemistry (IHC) staining was performed using specific mouse monoclonal antibody HE12 (Abcam) and scored as percentage of invasive nuclei stained (0-100%). CCNE1 and cyclin E1 correlations were explored using Pearson coefficients. Cox regression models were used for progression free-survival (PFS) analyses using expression levels split by median, to define high ( > median values) vs. low expression. Site of disease and prior chemotherapy were used as confounders in multivariate models. Results: Analyses were conducted in 219 pts (47% receiving PAL + FUL and 53% CAPE) with available tumors, with the analysed patients representative of the overall study. Most samples were from the archival primary (72%), obtained > 5 years before this analysisº (74%). CCNE1 and cyclin E1 were only moderately correlated (r = 0.5). Median CCNE1 was higher in metastatic vs primary (7.37 vs 6.94, p < 0.01), and in luminal B and non-luminal subtypes compared to luminal A (p < 0.001). In patients with high CCNE1 expression, median PFS on CAPE was 10.35 and PAL + FUL was 5.68 (HR = 1.63, 95% CI 1.02-2.59, p = 0.042). In patients with low CCNE1 expression, median PFS on CAPE was 9.43 and PAL + FUL was 8.97 (adjusted HR = 0.93, 95% CI 0.59-1.48, p = 0.762, interaction p = 0.072). Median cyclin E1 protein was higher in luminal B and non-luminal subtypes compared to luminal A (p < 0.01). Cyclin E1 protein expression was not predictive of treatment effect (high cyclin E1 expression CAPE vs PAL + FUL HR = 1.17, low cyclin E1 expression CAPE vs PAL + FUL HR = 1.21, interaction p = 0.977). Conclusions: High tumor CCNE1 mRNA expression identified patients with relative resistance to palbociclib plus fulvestrant, validating prior observations although without statistical significance for interaction. Assessment of Cyclin E1 protein expression did not show predictive value. Investigation treatments to enhance CDK4/6 inhibitor efficacy in tumors with high CCNE1 expression is warranted. Clinical trial information: NCT02028507 .

Efficacy and safety of weekly paclitaxel in elderly patients with heavily pretreated platinum-resistant ovarian carcinoma

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Background: In platinum-resistant ovarian cancer treatment, single-agent paclitaxel can be used alone or in combination with bevacizumab. We aimed to assess the efficacy and safety profile of a weekly paclitaxel (WP) scheme in heavily pretreated platinum-resistant high-grade serous ovarian carcinoma. Methods: We retrospectively analyzed 30 adult patients with platinum-resistant high-grade serous ovarian carcinoma treated with WP at our institution between 2015 and 2020. Patients with platinum-resistant ovarian, fallopian tube or primary carcinoma of the peritoneum who had received at least 3 doses of WP (80 mg/m2) alone or in combination with bevacizumab until disease progression or unacceptable toxicity were included in the analysis. Progression-free survival was assessed according to the Response Evaluation Criteria in Solid Tumors version 1.1. Information about toxicity was gathered from medical reports and lab tests. Kaplan-Meier curves and Log-rank test were performed for survival estimates. Results: In our sample, the median age was 68 years (IQR: 60-75) and the median number of previous lines of systemic treatment was 3 (range 1-5). 40% of patients received WP in combination with bevacizumab. The disease control rate was 60.7% (42.9% partial response and 17.8% stable disease). In the overall analysis, the median progression-free survival (mPFS) was 5.0 months (95% CI: 2.0-7.1 months). The presence of ascites significantly shortened the mPFS compared to patients without it (1.1 vs 5.1 months, p < 0.001). Even though the addition of bevacizumab to WP improved the mPFS, the difference was not statistically significant compared to WP alone (7.1 vs 4.06 months, p=0.30). Peripheral neuropathy was the most common adverse event (78% all grades, 18% grade 3). No grade 3 hematologic toxicity was registered. Treatment was discontinued in 6 patients (20%) – 4 due to peripheral neuropathy and two because of toxicoderma. Conclusions: In our sample, WP was an active and safe regimen in heavily pretreated platinum-resistant ovarian carcinoma. WP was well tolerated in elderly patients. The presence of ascites was associated to a shorter PFS in patients treated with WP compared to ascites-free patients.

eMonarcHER: A phase 3 study of abemaciclib plus standard adjuvant endocrine therapy in patients with HR+, HER2+, node-positive, high-risk early breast cancer

TPS596

Background: Hormone receptor positive (HR+), human epidermal growth factor receptor 2-positive (HER2+) breast cancer (BC) with high-risk characteristics has a high risk of disease recurrence. Novel therapeutic options for this population are urgently needed. Abemaciclib is an oral, selective, and potent CDK4 & 6 inhibitor administered on a continuous schedule which is approved for HR+, HER2- advanced BC (ABC) as monotherapy and in combination with endocrine therapy (ET). Abemaciclib combined with ET demonstrated a statistically significant improvement in invasive disease-free survival (IDFS) in participants (pt) with HR+, HER2-, node-positive, high risk early breast cancer (EBC) and also clinical activity in HR+, HER2+ ABC. The eMonarcHER trial investigates whether abemaciclib plus ET will improve IDFS in pts with HR+, HER2+, node-positive, high risk EBC. Methods: eMonarcHER is a phase 3 global, randomized, double-blinded, placebo (PB)-controlled trial in participants with HR+, HER2+, node-positive, high risk EBC who have completed adjuvant HER2-targeted therapy (tx). Eligible participants are randomized 1:1 to receive either abemaciclib 150 mg twice daily or PB, plus standard ET. Study intervention period will be ≤26 cycles (approximately 2 years) followed by ≤8 years of ET as medically indicated. Participants must have undergone definitive surgery of the primary breast tumor and have high-risk disease. High-risk disease is defined as (i) detection of residual axillary nodal disease at the time of definitive surgery in participants with prior neoadjuvant (neoadj) tx; or (ii) in patients not receiving neoadj tx, must have either ≥4 pathologically positive axillary lymph nodes (pALNs), or 1-3 pathological pALNs and either: histologic Grade 2-3 and/or primary invasive tumor size ≥5 cm. Participants must have received either adjuvant pertuzumab plus trastuzumab with chemotherapy or adjuvant T-DM1. Stratification factors include treatment with neoadj tx, menopausal status, and region. The study is powered at approximately 80% to detect the superiority of abemaciclib plus ET over PB plus ET in terms of IDFS (as defined by the STEEP system) at a 1-sided α =.025 using a log-rank test. Assuming a hazard ratio of 0.73, this requires approximately 324 events at final IDFS analysis. Key secondary objectives include overall survival, distant relapse free survival, safety, pharmacokinetics, and patient-reported outcomes. The study is planned to start in March 2021. Approximately 525 centers in 23 countries plan to enroll ̃2450 participants. Clinical trial information: NCT04752332.

Impact of duration of prior cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) therapy on alpelisib (ALP) benefit in patients (pts) with hormone receptor–positive (HR+), human epidermal growth factor receptor-2–negative (HER2–), PIK3CA-mutated advanced breast cancer (ABC) from BYLieve

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Background: Mutations in PIK3CA (encoding PI3Kα) are present in ̃40% of HR+, HER2– ABC tumors and are associated with relative endocrine resistance and poor prognosis. ALP inhibits and degrades PI3Kα. Primary analyses of Cohorts A and B from the phase 2 BYLieve study demonstrated that ALP + endocrine therapy (ET; fulvestrant [FUL] or letrozole [LET]) is effective and safe in pts with HR+, HER2– PIK3CA-mutated ABC with prior CDK4/6i therapy. Here, we evaluate if duration of prior CDK4/6i-based therapy impacts benefit of ALP + ET in these 2 cohorts. Methods: Cohorts A and B of BYLieve included pre/postmenopausal women who received CDK4/6i + AI or FUL, respectively, as immediate prior therapy. Cohort A received ALP 300 mg PO QD + FUL 500 mg IM Q28D + C1D15; Cohort B received ALP 300 mg PO QD + LET 2.5 mg PO QD. Within each cohort, pts were divided into 2 subgroups per duration of prior CDK4/6i therapy (“high”/”low,” above/below median duration of therapy) and the association of progression-free survival (PFS) with this covariate was analyzed using stratified log-rank test and Cox PH model. This analysis included pts for whom duration of prior CDK4/6i therapy was known, and efficacy was assessed in pts with centrally confirmed PIK3CA mutation in tumor tissue. Results: Of the 126 pts in Cohort A with duration of prior CDK4/6i available, 120 had centrally confirmed PIK3CA-mutated disease; 60 were exposed to CDK4/6i for > 380 days (high) and 60 for < 380 days (low), with similar demographics/disease characteristics between subgroups. There was no significant difference in PFS between the high vs low subgroups (HR 1.03; 95% CI, 0.64-1.64; P= 0.927; median 8.0 vs 7.0 mo). Grade ≥3 adverse events (AEs) were experienced by 66.9% (n = 85) of all pts in Cohort A and 66.7% (n = 42)/68.3% (n = 43) in the high/low subgroups, respectively. Of the 123 pts in Cohort B with duration of prior CDK4/6i available, 113 had centrally confirmed PIK3CA-mutated disease; 57 were exposed to CDK4/6i for > 305 days (high) and 56 for < 305 days (low), with similar demographics/disease characteristics between subgroups. There was no significant difference in PFS between high vs low subgroups (HR 1.20; 95% CI, 0.78-1.84; P= 0.400; median 5.4 vs 5.9 mo). Grade ≥3 AEs were experienced by 69.8% (n = 88) of all pts in Cohort B and 71.0% (n = 44)/68.9% (n = 42) in the high/low subgroups, respectively. Conclusions: This analysis demonstrates that the benefit and safety profiles of ALP + ET are similar in pts with HR+, HER2– PIK3CA-mutated ABC who achieved relatively shorter duration of disease control with prior CDK4/6i vs those with longer duration of disease control, and suggests that ALP overcomes acquired resistance to CDK4/6i in these pts. Clinical trial information: NCT03056755 .

Abstract PD2-06: Clinical outcomes of alpelisib plus fulvestrant in hormone receptor-positive, human epidermal growth factor receptor-2-negative advanced breast cancer with PIK3CA alterations detected in plasma ctDNA by next-generation sequencing: Biomarker analysis from the SOLAR-1 study

Introduction: The PI3K pathway is often hyperactivated in cancer as a result of an altered PI3K isoform and/or loss of phosphatase and tensin homolog function. Approximately 40% of patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor-2-negative (HER2−) advanced breast cancer (ABC) have tumors with mutations in PIK3CA, which encodes the α-isoform of PI3K, p110α. These mutations are known to cause hyperactivation of the PI3K pathway, which contributes to cell proliferation, drug resistance, and poor prognoses. Alpelisib (ALP) is an α-selective PI3K inhibitor that, in combination with fulvestrant (FUL), prolonged median progression-free survival (mPFS) in pts with HR+, HER2−, PIK3CA-mutant ABC following progression on/after prior aromatase inhibitor in the phase 3 SOLAR-1 trial. In SOLAR-1, prospective PIK3CA mutation testing was performed on tumor tissue using PCR-based assays. Through retrospective analysis, efficacy of ALP was demonstrated in subgroups of pts with PIK3CA alteration(s) in tumor tissue and mutation(s) in ctDNA, detected by next-generation sequencing (NGS) and PCR, respectively. In this exploratory biomarker analysis, we assessed clinical outcomes of pts with PIK3CA alteration(s), detected in ctDNA by NGS.Methods: SOLAR-1 is a phase 3, randomized, double-blind, placebo-controlled study of ALP 300 mg vs placebo taken daily with FUL 500 mg every 28 days + Cycle 1 Day 15 in men and postmenopausal women with HR+, HER2- ABC. Retrospectively, the full exonic region of the PIK3CA gene was sequenced using the Foundation Medicine 324-gene ctDNA panel in plasma ctDNA collected at baseline. mPFS was assessed using Kaplan-Meier methodology per investigator assessment.Results: Of 572 pts in SOLAR-1, 381 pts (66.6%) across both PIK3CA-mutant and nonmutant cohorts had valid plasma ctDNA data. Of these pts, 193 (50.7%) had a PIK3CA alteration; 168 (87%) had PCR-detectable mutations and 147 (76%) had a single alteration. A total of 70 (36%) and 102 (53%) pts had alterations in exons 9 and 20, respectively. ALP plus FUL prolonged mPFS in pts with PIK3CA alterations detected in plasma ctDNA by NGS (n=101; Table). Clinical benefit was also observed in pts with PCR-detectable mutations (n=88), single mutations (n=83), and pts with mutations in exon 9 (n=34) and exon 20 (n=54). Pt numbers were low, and wide 95% CIs were observed in groups with alterations not detectable by PCR (n=13) and in pts with multiple alterations. Some limitations of this retrospective plasma analysis include that this is a subgroup (66.6%) of the SOLAR-1 pt population and that the subgroup of pts with non-altered PIK3CA included pts with a PIK3CA mutation in their tumor tissue. Conclusions: ALP plus FUL demonstrated clinical benefit in pts with PIK3CA mutations detected in plasma ctDNA by NGS, in pts with single alterations, and in pts with alterations in exons 9 and 20. Results were consistent across pt groups, except in those with alterations not detectable by PCR. In conclusion, these data demonstrate a consistent clinical benefit of ALP plus FUL in various groups of pts with PIK3CA alterations detected in ctDNA by NGS.

Clinical Outcomes of Patients With PIK3CA Alterations Detected in Plasma ctDNA by NGS in SOLAR-1Alpelisib + fulvestrantPlacebo + fulvestrantHR (95% CI)Events/N (%)mPFS, mo (95% CI)Events/N(%)mPFS, mo (95% CI)PIK3CA altered vs non-alteredAltered58/101(57.4)11.04(7.72-16.16)73/92(79.3)3.65(2.86-6.80)0.47(0.33-0.67)Non-altered40/87(46.0)10.87(5.59-16.76)60/101(59.4)5.45(3.75-9.00)0.60(0.40-0.91)PIK3CA: alteration detectable by PCR vs alteration not detectable by PCRDetectable52/88(59.1)12.48(7.36-18.37)66/80(82.5)3.58(2.37-5.65)0.44(0.30-0.64)Not detectable6/13(46.2)8.48(2.69-NA)7/12(58.3)7.39(1.87-12.98)1.12(0.35-3.56)PIK3CA: number of alterationsSingle45/83(54.2)12.88(7.36-18.50)50/64(78.1)3.58(1.87-6.11)0.43(0.28-0.65)Multiple13/18(72.2)9.00(3.68-18.37)23/28(82.1)4.63(3.48-9.63)0.55(0.25-1.20)PIK3CA alterations in exon 9 or exon 20Exon 918/34(52.9)15.21(7.03-NA)29/36(80.6)3.66(2.86-7.36)0.31(0.16-0.61)Exon 2034/54(63.0)10.91(5.72-18.37)40/48(83.3)3.52(1.87-6.11)0.51(0.31-0.82)CI, confidence interval; ctDNA, circulating tumor DNA; HR, hazard ratio; mPFS, median progression-free survival; mo, months; NA, not available; NGS, next-generation sequencing.

Citation Format: Eva M. Ciruelos, Sibylle Loibl, Ingrid A. Mayer, Mario Campone, Hope S. Rugo, Monica Arnedos, Hiroji Iwata, Pier Franco Conte, Fabrice André, Albert Reising, Chong Ma, Michelle Miller, Naveen Babbar, Dejan Juric. Clinical outcomes of alpelisib plus fulvestrant in hormone receptor-positive, human epidermal growth factor receptor-2-negative advanced breast cancer with PIK3CA alterations detected in plasma ctDNA by next-generation sequencing: Biomarker analysis from the SOLAR-1 study [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD2-06.

Abstract PS2-01: Plk1 expression & efficacy of palbociclib in advanced hormonal receptor-positive breast cancer patients from PEARL study (GEICAM 2012-03)

Background: CDK 4/6 inhibitors (CDK 4/6i) with endocrine therapy (ET) combination therapy have improved outcomes in patients (pts) with hormonal receptor positive (HR+)/human epidermal growth factor receptor negative (HER2-) advanced breast cancer (ABC). However, most pts eventually develop resistance to these drugs, and one third never respond. Aside from HR positivity, predictive markers of clinical benefit from CDK 4/6i remains elusive. We aimed to identify biomarkers of response to palbociclib (PAL) and analyze potential therapeutic targets to reverse resistance. Methods: PEARL trial is a multicenter phase 3 study that assigned 601 postmenopausal HR+/HER2- ABC pts, whose disease progressed on aromatase inhibitors (AIs), to receive PAL + ET vs capecitabine (CAPE). We performed a differential gene expression analysis in pre-treatment tumors in extreme responders to PAL using the HTG EdgeSeq Oncology Biomarker Panel (HTG Molecular Diagnostics, Inc.), containing 2534 cancer related genes. Samples were subset in 2 categories: refractory (progressive disease as best response) vs sensitive (progression-free survival (PFS) within the upper quartile). Cox regression and Significance Analysis of Microarrays (SAM) analysis adjusting for multiple comparisons were performed. Results: We analyzed 455 (75.7%) pts with pre-treatment tumors available [from them, PAL + ET arm: 229 (50.3%) pts; CAPE arm: 226 (49.7%) pts]. Fifty genes (false discovery rate (FDR)&lt;0.05) were differentially expressed in pts sensitive vs refractory to PAL (E2F target genes, epithelial-to-mesenchymal transition (EMT) and cell cycle genes, mainly). Unsupervised hierarchical clustering of pts based on the expression of these genes revealed two clusters. Cluster 1 is composed mostly of resistant tumors, highly proliferative (Ki67≥20%: 70%) with a great proportion of luminal B (59%) and non-luminal tumors (19%). Cluster 2 is composed of sensitive, low proliferative (Ki67&lt;20%: 58%), mostly luminal A tumors (75%). There was no difference in ESR1 mutations distribution between the two clusters (Table 1). Forty genes were up-regulated and associated with resistance, including CCNE1 and PLK1 (Polo Like Kinase 1). In the whole cohort, pts with high levels (&gt; median) of PLK1 (PLK1-high) treated with PAL, had a worse PFS in a multivariate model (5.7 months (m) vs 9.3 m of median PFS in PLK1-High vs -Low; HR=1.64, 95% CI (1.25-2.34), p=0.0008; adjusted model for confounders: age, site of disease, sites of metastasis, prior chemotherapy and Ki67). There were no differences in population treated with CAPE (9.9 m vs 9.4 m, PLK1-High vs -Low; HR=0.82, 95% CI (0.56-1.21), p=0.3189). In the METABRIC cohort, PLK1-High was associated with worse overall survival in HR+/HER2- BC but not in triple negative nor in HER2+ tumors. Among HR+/HER2- tumors, PLK1 expression was higher in luminal B and HER2-enriched intrinsic subtypes. We interrogated DepMap database and found that in BC cells lines there was an inverse correlation between PLK1 expression and effect on cell viability of CDK4 CRISPR knock-out (Pearson correlation r:0.54, p=0.009), but not of CDK6 knock-out. Also, HR+/HER2-/High Ki67 BC cell lines (HCC1428, EFM19 and MCF7) showed resistance to PAL on cell proliferation assays but sensitivity to the PLK1 inhibitor BI-2536. Conclusion: High expression of PLK1 is associated with intrinsic resistance to PAL and ET, this might be overcome with PLK1 inhibition.

Table 1PATIENT CHARACTERISTICSCluster 1Cluster 2ALLn=57n=47n=104RespondersSensitive42 (73.68%)14 (29.79%)56 (53.85%)Refractory15 (26.32%)33 (70.21%)48 (46.15%)ESR1Mutated9 (15.79%)13 (27.66%)22 (21.15%)Wild type45 (78.95%)34 (72.34%)79 (75.96%)Unknown3 (5.26%)0 (0%)3 (2.88%)PriorQTN42 (73.68%)31 (65.96%)73 (70.19%)Y15 (26.32%)16 (34.04%)31 (29.81%)SubtypeLumA43 (75.44%)10 (21.28%)53 (50.96%)LumB14 (24.56%)28 (59.57%)42 (40.38%)Non Luminal0 (0%)9 (19.15%)9 (8.65%)MetastasisOne21 (36.84%)15 (31.91%)36 (34.62%)Multiple36 (63.16%)32 (68.09%)68 (65.38%)KI67 20%KI67&lt;2033 (57.89%)7 (14.89%)40 (38.46%)KI67≥2016 (28.07%)33 (70.21%)49 (47.12%)Unknown8 (14.04%)7 (14.89%)15 (14.42%)Objective ResponseComplete1 (1.75%)0 (0%)1 (0.96%)Partial16 (28.07%)6 (12.77%)22 (21.15%)Progressive15 (26.32%)33 (70.21%)48 (46.15%)Stable25 (43.86%)8 (17.02%)33 (31.73%)

Citation Format: Angel Guerrero- Zotano, Christoph Zielinski, Miguel Gil-Gil, Manuel Ruiz-Borrego, Eva M. Ciruelos, Montserrat Munoz, Begoña Bermejo, Mireia Margeli, Antonio Antón, Tibor Csöszi, Andrés García-Palomo, Ana Santaballa, Jose Luis Alonso, Antonio Fernández, Massimo Corsaro, Jesús Herranz, Paula López, Rosalia Caballero, Christiane Thallinger, Miguel Martin. Plk1 expression & efficacy of palbociclib in advanced hormonal receptor-positive breast cancer patients from PEARL study (GEICAM 2012-03) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS2-01.

Circulating tumor DNA dynamics in advanced breast cancer treated with CDK4/6 inhibition and endocrine therapy

Circulating tumor DNA (ctDNA) levels may predict response to anticancer drugs, including CDK4/6 inhibitors and endocrine therapy combinations (CDK4/6i+ET); however, critical questions remain unanswered such as which assay or statistical method to use. Here, we obtained paired plasma samples at baseline and week 4 in 45 consecutive patients with advanced breast cancer treated with CDK4/6i+ET. ctDNA was detected in 96% of cases using the 74-gene Guardant360 assay. A variant allele fraction ratio (VAFR) was calculated for each of the 79 detected mutations between both timepoints. Mean of all VAFRs (mVAFR) was computed for each patient. In our dataset, mVAFR was significantly associated with progression-free survival (PFS). Baseline VAF, on-treatment VAF or absolute changes in VAF were not associated with PFS, nor were CA-15.3 levels at baseline, week 4 or the CA-15.3 ratio. These findings demonstrate that ctDNA dynamics using a standardized multi-gene panel and a unique methodological approach predicts treatment outcome. Clinical trials in patients with an unfavorable ctDNA response are needed.

Palbociclib in combination with endocrine therapy versus capecitabine in hormonal receptor-positive, human epidermal growth factor 2-negative, aromatase inhibitor-resistant metastatic breast cancer: a phase III randomised controlled trial-PEARL

BACKGROUND

Palbociclib plus endocrine therapy (ET) is the standard treatment of hormone receptor-positive and human epidermal growth factor receptor 2-negative, metastatic breast cancer (MBC). However, its efficacy has not been compared with that of chemotherapy in a phase III trial.

PATIENTS AND METHODS

PEARL is a multicentre, phase III randomised study in which patients with aromatase inhibitor (AI)-resistant MBC were included in two consecutive cohorts. In cohort 1, patients were randomised 1 : 1 to palbociclib plus exemestane or capecitabine. On discovering new evidence about estrogen receptor-1 (ESR1) mutations inducing resistance to AIs, the trial was amended to include cohort 2, in which patients were randomised 1 : 1 between palbociclib plus fulvestrant and capecitabine. The stratification criteria were disease site, prior sensitivity to ET, prior chemotherapy for MBC, and country of origin. Co-primary endpoints were progression-free survival (PFS) in cohort 2 and in wild-type ESR1 patients (cohort 1 + cohort 2). ESR1 hotspot mutations were analysed in baseline circulating tumour DNA.

RESULTS

From March 2014 to July 2018, 296 and 305 patients were included in cohort 1 and cohort 2, respectively. Palbociclib plus ET was not superior to capecitabine in both cohort 2 [median PFS: 7.5 versus 10.0 months; adjusted hazard ratio (aHR): 1.13; 95% confidence interval (CI): 0.85-1.50] and wild-type ESR1 patients (median PFS: 8.0 versus 10.6 months; aHR: 1.11; 95% CI: 0.87-1.41). The most frequent grade 3-4 toxicities with palbociclib plus exemestane, palbociclib plus fulvestrant and capecitabine, respectively, were neutropenia (57.4%, 55.7% and 5.5%), hand/foot syndrome (0%, 0% and 23.5%), and diarrhoea (1.3%, 1.3% and 7.6%). Palbociclib plus ET offered better quality of life (aHR for time to deterioration of global health status: 0.67; 95% CI: 0.53-0.85).

CONCLUSIONS

There was no statistical superiority of palbociclib plus ET over capecitabine with respect to PFS in MBC patients resistant to AIs. Palbociclib plus ET showed a better safety profile and improved quality of life.

Alpelisib plus fulvestrant for PIK3CA-mutated, hormone receptor-positive, human epidermal growth factor receptor-2-negative advanced breast cancer: final overall survival results from SOLAR-1

BACKGROUND

Activation of the phosphatidylinositol-3-kinase (PI3K) pathway via PIK3CA mutations occurs in 28%-46% of hormone receptor-positive (HR+), human epidermal growth factor receptor-2-negative (HER2-) advanced breast cancers (ABCs) and is associated with poor prognosis. The SOLAR-1 trial showed that the addition of alpelisib to fulvestrant treatment provided statistically significant and clinically meaningful progression-free survival (PFS) benefit in PIK3CA-mutated, HR+, HER2- ABC.

PATIENTS AND METHODS

Men and postmenopausal women with HR+, HER2- ABC whose disease progressed on or after aromatase inhibitor (AI) were randomized 1 : 1 to receive alpelisib (300 mg/day) plus fulvestrant (500 mg every 28 days and once on day 15) or placebo plus fulvestrant. Overall survival (OS) in the PIK3CA-mutant cohort was evaluated by Kaplan-Meier methodology and a one-sided stratified log-rank test was carried out with an O'Brien-Fleming efficacy boundary of P ≤ 0.0161.

RESULTS

In the PIK3CA-mutated cohort (n = 341), median OS [95% confidence interval (CI)] was 39.3 months (34.1-44.9) for alpelisib-fulvestrant and 31.4 months (26.8-41.3) for placebo-fulvestrant [hazard ratio (HR) = 0.86 (95% CI, 0.64-1.15; P = 0.15)]. OS results did not cross the prespecified efficacy boundary. Median OS (95% CI) in patients with lung and/or liver metastases was 37.2 months (28.7-43.6) and 22.8 months (19.0-26.8) in the alpelisib-fulvestrant and placebo-fulvestrant arms, respectively [HR = 0.68 (0.46-1.00)]. Median times to chemotherapy (95% CI) for the alpelisib-fulvestrant and placebo-fulvestrant arms were 23.3 months (15.2-28.4) and 14.8 months (10.5-22.6), respectively [HR = 0.72 (0.54-0.95)]. No new safety signals were observed with longer follow-up.

CONCLUSIONS

Although the analysis did not cross the prespecified boundary for statistical significance, there was a 7.9-month numeric improvement in median OS when alpelisib was added to fulvestrant treatment of patients with PIK3CA-mutated, HR+, HER2- ABC. Overall, these results further support the statistically significant prolongation of PFS observed with alpelisib plus fulvestrant in this population, which has a poor prognosis due to a PIK3CA mutation. CLINICALTRIALS.

GOV ID

NCT02437318.

Capivasertib, an AKT Kinase Inhibitor, as Monotherapy or in Combination with Fulvestrant in Patients with AKT1 E17K-Mutant, ER-Positive Metastatic Breast Cancer

PURPOSE

The activating mutation AKT1 E17K occurs in approximately 7% of estrogen receptor-positive (ER+) metastatic breast cancer (MBC). We report, from a multipart, first-in-human, phase I study (NCT01226316), tolerability and activity of capivasertib, an oral AKT inhibitor, as monotherapy or combined with fulvestrant in expansion cohorts of patients with AKT1 E17K-mutant ER+ MBC.

PATIENTS AND METHODS

Patients with an AKT1 E17K mutation, detected by local (next-generation sequencing) or central (plasma-based BEAMing) testing, received capivasertib 480 mg twice daily, 4 days on, 3 days off, weekly or 400 mg twice daily combined with fulvestrant at the labeled dose. Study endpoints included safety, objective response rate (ORR; RECIST v1.1), progression-free survival (PFS), and clinical benefit rate at 24 weeks (CBR24). Biomarker analyses were conducted in the combination cohort.

RESULTS

From October 2013 to August 2018, 63 heavily pretreated patients received capivasertib (20 monotherapy, 43 combination). ORR was 20% with monotherapy, and within the combination cohort was 36% in fulvestrant-pretreated and 20% in fulvestrant-naïve patients, although the latter group may have had more aggressive disease at baseline. AKT1 E17K mutations were detectable in plasma by BEAMing (95%, 41/43), droplet digital PCR (80%, 33/41), and next-generation sequencing (76%, 31/41). A ≥50% decrease in AKT1 E17K at cycle 2 day 1 was associated with improved PFS. Combination therapy appeared more tolerable than monotherapy [most frequent grade ≥3 adverse events: rash (9% vs. 20%), hyperglycemia (5% vs. 30%), diarrhea (5% vs. 10%)].

CONCLUSIONS

Capivasertib demonstrated clinically meaningful activity in heavily pretreated patients with AKT1 E17K-mutant ER+ MBC, including those with prior disease progression on fulvestrant. Tolerability and activity appeared improved by the combination.

Phase III study to evaluate patient's preference of subcutaneous versus intravenous trastuzumab in HER2-positive metastatic breast cancer patients: Results from the ChangHER study (GEICAM/2012-07)

OBJECTIVE

We compared patients' preferences for intravenous (IV-t) versus subcutaneous (SC-t) trastuzumab administration.

METHODS

Phase III, open-label, multicentre study in HER2-positive metastatic breast cancer. Patients were receiving IV-t for at least 4 months without progression. Randomisation was 1:1 to administer 2 cycles of SC-t with vial followed by 2 cycles with single injection device (SID) or the reverse sequence (600mg SC-t every 3 weeks for 4 cycles).

PRIMARY OBJECTIVE

patients' preference for IV-t versus SC-t; secondary objectives: patients' preference for vial versus SID, healthcare professional (HCP) preference and safety.

RESULTS

We randomised 166 patients in 26 sites. Median number of previous lines of chemotherapy and/or endocrine therapy was 1 (1-7). Median duration of prior IV-t was 1.8 years (0.3-14). Of the159 patients completing the questionnaires, 86.2% preferred SC-t, 6.9% preferred IV-t, and 6.9% had no preference. Patients preferred SID (59.2%) over vial (26.3%). Most (87.2%) HCP preferred SC-t of whom 51.3% and 28.2% preferred SID and vial respectively. Related adverse events included G1-2 injection site reactions in 18 patients (10.8%), G1 pain in 8 (4.8%), G1-2 allergic reaction in 2 (1.2%), one G3 heart failure and 1 G2 ejection fraction decrease.

CONCLUSIONS

SC-t is preferred with no safety impact.

Time course and management of key adverse events during the randomized phase III SOLAR-1 study of PI3K inhibitor alpelisib plus fulvestrant in patients with HR-positive advanced breast cancer

BACKGROUND

Alpelisib (α-selective phosphatidylinositol 3-kinase inhibitor) plus fulvestrant is approved in multiple countries for men and postmenopausal women with PIK3CA-mutated, hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer following progression on or after endocrine therapy. A detailed understanding of alpelisib's safety profile should inform adverse event (AE) management and enhance patient care.

PATIENTS AND METHODS

AEs in the phase III SOLAR-1 trial were assessed in patients with and without PIK3CA mutations. The impact of protocol-specified AE-management recommendations was evaluated, including an amendment to optimize hyperglycemia and rash management.

RESULTS

Patients were randomly assigned to receive fulvestrant plus alpelisib (n = 284) or placebo (n = 287). The most common grade 3/4 AEs with alpelisib were hyperglycemia (grade 3, 32.7%; grade 4, 3.9%), rash (grade 3, 9.9%), and diarrhea (grade 3, 6.7%). Median time to onset of grade ≥3 toxicity was 15 days (hyperglycemia, based on fasting plasma glucose), 13 days (rash), and 139 days (diarrhea). Metformin alone or in combination with other antidiabetic agents was used by most patients (87.1%) with hyperglycemia. Preventive anti-rash medication resulted in lower incidence (any grade, 26.7% versus 64.1%) and severity of rash (grade 3, 11.6% versus 22.7%) versus no preventative medication. Discontinuations due to grade ≥3 AEs were lower following more-detailed AE management guidelines (7.9% versus 18.1% previously). Patients with PIK3CA mutations had a median alpelisib dose intensity of 248 mg/day. Median progression-free survival with alpelisib was 12.5 and 9.6 months for alpelisib dose intensities of ≥248 mg/day and <248 mg/day, respectively, compared with 5.8 months with placebo.

CONCLUSIONS

Hyperglycemia and rash occurred early during alpelisib treatment, while diarrhea occurred at a later time point. Early identification, prevention, and intervention, including concomitant medications and alpelisib dose modifications, resulted in less severe toxicities. Reductions in treatment discontinuations and improved progression-free survival at higher alpelisib dose intensities support the need for optimal AE management. CLINICALTRIALS.

GOV ID

NCT02437318.

Abstract P6-18-17: Ribociclib + letrozole in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) advanced breast cancer (aBC) with no prior endocrine therapy (ET) for ABC: CompLEEment-1 trial, preliminary results from Spanish population

Background: The phase III Monaleesa-2, Monaleesa-3 and Monaleesa-7 trials have shown significantly improved PFS for the combination ribociclib + ET vs ET + placebo in pre-, peri-, and postmenopausal women with HR+/HER2–, first and second line aBC. The Compleement-1 trial is a phase IIIb, single-arm, open-label, international study to assess the safety and efficacy of ribociclib + letrozole in men and women who have not received prior ET for HR+, HER2– ABC [J Clin Oncol 36, 2018 (suppl; abstr 1056)].

Methods: 526 patients with HR+, HER2– ABC, ≤1 line of prior CT, and no prior ET for aBC were enrolled in the Compleement-1trial in Spain from April 2017 to January 2018. Patients received ribociclib (600 mg/day, 3 weeks on/1 week off) + letrozole (2.5 mg/day); men and premenopausal women received concomitant goserelin (3.6 mg subcutaneous implant every 28 days). The primary objective was safety and tolerability. Here we report on a sub-analysis from the Spanish population of Compleement-1 trial including baseline characteristics and early safety results for the first patients enrolled who completed at least 56 days of follow-up or discontinued before the cut-off date (3rd Oct 2017).

Results: One hundred fifty four patients constituted the analytical cohort for this sub-analysis. Demographics and baseline characteristics: median age was 52 years (range 24-82); 1% of patients were male, 31.8% female pre-menopausal and 67.5% female post-menopausal; 44.2% vs 38.3% of patients had visceral disease vs bone only disease; 49.9% patients had ≥2 metastatic sites; and 34.4% of patients presented as de novo stage IV. The median exposure for study treatment was 1.8 months (range 0.8-1.8). The grade 3/4 events reported &gt;1% included neutropenia (50%), increased GGT levels (3.2%), leukopenia (1.3%), and increased ALT (1.3%). QTcF prolongation &gt;480ms based on ECG data was reported in 1.2% patients. Median dose intensity for ribociclib was 600mg/day (range 476.5-600); 11% of patients required one dose reduction (8.4% due to AEs), 59.7% had at least one dose interruption (57.1% due to AEs) and 9.7% were permanently discontinued (4.5% due to AEs).

Conclusions: Preliminary safety results from this Compleement-1 sub-analysis including Spanish population are consistent with previous data presented from Monaleesa-2, Monaleesa-3, Monaleesa-7 and Compleement-1. These data support the predictable and manageable safety profile of ribociclib in combination with letrozole. Clinical trial information: NCT02941926

Citation Format: Salvador J, Ciruelos EM, Prat A, Jiménez-Rodríguez B, de la Cruz L, Martínez N, Villanueva Vázquez R, de Toro R, Antón A, Moreno F, Alvarez I, Gavila J, Quiroga V, Vicente E, de la Haba J, González-Santiago S, Díaz N, Barnadas A, Cantos Sánchez de Ibargüen B, Delgado JI, Bellet M, Gimeno A, Sanz S, Martin M. Ribociclib + letrozole in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) advanced breast cancer (aBC) with no prior endocrine therapy (ET) for ABC: CompLEEment-1 trial, preliminary results from Spanish population [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-18-17.

Abstract GS4-02: Randomized comparison of adjuvant aromatase inhibitor exemestane (E) plus ovarian function suppression (OFS) vs tamoxifen (T) plus OFS in premenopausal women with hormone receptor positive (HR+) early breast cancer (BC): Update of the combined TEXT and SOFT trials

Background: The combined results of TEXT and SOFT, after 5.7 years median follow-up, found adjuvant E+OFS significantly improved disease-free survival (DFS) vs T+OFS in premenopausal women with HR+ BC (Pagani et al, NEJM 2014). Follow-up was immature for overall survival (OS). We report a planned update with visit cut-off of 31Dec16 after 9 years median follow-up.

Methods: TEXT and SOFT enrolled premenopausal women with HR+ early BC from Nov 2003 to Apr 2011 (2660 TEXT, 3047 SOFT in the intention-to-treat populations). TEXT randomized women within 12wk of surgery to 5 yrs E+OFS vs T+OFS; chemotherapy (CT) was optional and concurrent with OFS. SOFT randomized women to 5 yrs E+OFS vs T+OFS vs T alone, within 12wk of surgery if no CT planned, or within 8mo of completing (neo)adjuvant CT after premenopausal status was (re-)established. OFS was by choice of 5yr GnRH agonist triptorelin, oophorectomy or ovarian irradiation. Both trials were stratified by CT use. The primary endpoint was DFS: randomization until invasive local, regional, distant recurrence or contralateral breast; invasive second malignancy; death. Secondary endpoints included invasive breast cancer-free interval (BCFI), distant recurrence-free interval (DRFI) and OS. Stratified Cox models estimated hazard ratios; Kaplan-Meier method estimated 8yr endpoint rates. NCT00066703/NCT00066690.

Results: DFS for patients assigned E+OFS (n=2346) continued to be significantly improved over T+OFS (n=2344): 8yr DFS was 86.8% vs. 82.8%. The 8yr BCFI was improved by 4.1% (89.3% vs 85.2%) and 8yr DRFI by 2.1% (91.8% vs 89.7%). There was no difference in OS in patients assigned E+OFS vs T+OFS: 93.4% vs 93.3% OS at 8yrs. For 1996 women without CT there have been 45 deaths, with 98% OS at 8yrs with both treatments.

EndpointN. EventsHazard Ratio (95% CI) E+OFS vs T+OFSDFS7200.77 (0.67-0.90); P&lt;0.001BCFI6000.74 (0.63-0.87)DRFI4330.80 (0.65-0.96)OS3200.98 (0.79-1.22)

Overall toxicity was not significantly worse with E+OFS than with T+OFS (32% vs 31% grade 3-4 targeted AEs). Hot flashes, musculoskeletal symptoms and hypertension were the most frequent targeted grade 3-4 AEs. Overall, 15% of patients stopped all protocol-assigned treatment early. Patients assigned E+OFS had increased risk of assigned oral endocrine therapy cessation (25% vs 19% for patients assigned T+OFS by 4yrs) but not of triptorelin cessation (18% vs 19% by 4yrs, respectively).

Conclusions: After 9 yrs median follow-up, adjuvant E+OFS, as compared with T+OFS, shows a sustained reduction of the risk of recurrence but did not improve overall survival. As in postmenopausal women, oncologists need to consider potential absolute benefits and properly select patients at sufficient risk for recurrence for whom E+OFS seems indicated. Follow-up continues, which will further clarify the effect of E+OFS for safety, late recurrence and overall survival.

Citation Format: Pagani O, Regan MM, Fleming GF, Walley BA, Colleoni M, Láng I, Gomez HL, Tondini C, Burstein HJ, Goetz MP, Ciruelos EM, Stearns V, Debled M, Martino S, Geyer Jr CE, Pinotti G, Coates AS, Goldhirsch A, Gelber RD, Francis PA. Randomized comparison of adjuvant aromatase inhibitor exemestane (E) plus ovarian function suppression (OFS) vs tamoxifen (T) plus OFS in premenopausal women with hormone receptor positive (HR+) early breast cancer (BC): Update of the combined TEXT and SOFT trials [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr GS4-02.

Abstract GS4-03: Randomized comparison of adjuvant tamoxifen (T) plus ovarian function suppression (OFS) versus tamoxifen in premenopausal women with hormone receptor-positive (HR+) early breast cancer (BC): Update of the SOFT trial

Background: The primary results of SOFT at 5.6 years median follow-up found adding OFS to T did not provide a significant benefit in the overall study population of premenopausal women with HR+ BC (Francis et al, NEJM 2015). For those women at sufficient risk for recurrence to warrant adjuvant chemotherapy (CT) and who remained premenopausal, the addition of OFS improved disease outcomes. Follow-up was immature for overall survival (OS). We report a planned update with visit cut-off of 31Dec16 after 8 yrs median follow-up.

Methods: SOFT randomized premenopausal women with HR+ BC from Nov 2003 to Jan 2011 to 5 yrs of T vs T+OFS vs Exemestane(E)+OFS. OFS was by choice of GnRH agonist triptorelin, oophorectomy or ovarian irradiation. SOFT was stratified by the use of prior CT; 47% received no CT and 53% remained premenopausal after prior CT, determined by premenopausal estradiol level within 8 months of CT completion. The primary endpoint was invasive disease-free survival (DFS; randomization until invasive local, regional, distant recurrence or contralateral breast; invasive second malignancy; death). Secondary endpoints included invasive breast cancer-free interval (BCFI), distant recurrence-free interval (DRFI) and OS. NCT00066690.

Results: DFS for patients assigned T+OFS (n=1015) was significantly improved over T (n=1018; HR=0.76 [95%CI 0.62-0.93]) and 8yr DFS was 83.2% vs 78.9%, respectively; BCFI and DRFI results were supportive (see Table). Hazard ratios for these 3 endpoints showed no heterogeneity by use of prior CT. For patients with prior CT, 8yr DFS was 76.7% with T+OFS vs 71.4% with T (Δ=5.3%); in those without CT, 8yr DFS was 90.6% vs 87.4% (Δ=3.2%). E+OFS (n=1014) improved outcomes relative to T (Table); 8yr DFS for E+OFS was 85.9% (80.4% with use of prior CT and 92.5% for those without CT). OS was improved with T+OFS vs T (8yr OS 93.3% vs 91.5%). 8yr OS was 92.1% with E+OFS. 201/225 deaths occurred in women with prior CT. For women without CT there have been 10, 5 and 9 deaths in the T+OFS, T and E+OFS groups (total n=1419), respectively, only half of these deaths after breast cancer event.

N. EventsHazard Ratio (95% CI)Endpoint(3 arms)T+OFS vs TE+OFS vs TDFS5180.76 (0.62-0.93) P=0.0090.65 (0.53-0.81)BCFI4370.76 (0.61-0.95)0.64 (0.51-0.81)DRFI3060.86 (0.66-1.13)0.73 (0.55-0.96)OS2250.67 (0.48-0.92)0.85 (0.62-1.15)

Overall toxicity was worse with T+ OFS than with T, including 32% vs 25% grade 3+ targeted AEs. Early cessation of tamoxifen occurred for 19% assigned T+OFS and 22% of women assigned T; the cumulative incidence of early cessation of triptorelin on the T+OFS arm was 23% by 4yrs. Early cessation of exemestane occurred for 28% and of triptorelin for 21% by 4yrs on the E+OFS arm.

Conclusions: With additional follow-up to a median of 8yrs, SOFT further supports the value of OFS for some premenopausal women. Follow-up continues, which will further clarify the safety and the benefit of OFS for late recurrence and overall survival. Oncologists appear to be able to select a low risk group (no chemotherapy) for whom treatment escalation is unlikely to improve survival.

Citation Format: Fleming G, Francis PA, Láng I, Ciruelos EM, Bellet M, Bonnefoi HR, Climent MA, Pavesi L, Burstein HJ, Martino S, Davidson NE, Geyer Jr CE, Walley BA, Coleman RE, Kerbrat P, Buchholz S, Ingle JN, Rabaglio-Poretti M, Colleoni M, Regan MM. Randomized comparison of adjuvant tamoxifen (T) plus ovarian function suppression (OFS) versus tamoxifen in premenopausal women with hormone receptor-positive (HR+) early breast cancer (BC): Update of the SOFT trial [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr GS4-03.

A phase II study of combined ridaforolimus and dalotuzumab compared with exemestane in patients with estrogen receptor-positive breast cancer

PURPOSE

Combining the mTOR inhibitor ridaforolimus and the anti-IGFR antibody dalotuzumab demonstrated antitumor activity, including partial responses, in estrogen receptor (ER)-positive advanced breast cancer, especially in high proliferation tumors (Ki67 > 15%).

METHODS

This randomized, multicenter, international, phase II study enrolled postmenopausal women with advanced ER-positive breast cancer previously treated with a nonsteroidal aromatase inhibitor (NCT01234857). Patients were randomized to either oral ridaforolimus 30 mg daily for 5 of 7 days (once daily [qd] × 5 days/week) plus intravenous dalotuzumab 10 mg/kg/week or oral exemestane 25 mg/day, and stratified by Ki67 status. Due to a high incidence of stomatitis in the ridaforolimus-dalotuzumab group, two sequential, nonrandomized, reduced-dose cohorts were explored with ridaforolimus 20 and 10 mg qd × 5 days/week. The primary endpoint was progression-free survival (PFS).

RESULTS

Median PFS was 21.4 weeks for ridaforolimus 30 mg qd × 5 days/week plus dalotuzumab 10 mg/kg (n = 29) and 24.3 weeks for exemestane (n = 33; hazard ratio = 1.00; P = 0.5). Overall survival and objective response rates were similar between treatment arms. The incidence of drug-related, nonserious, and serious adverse events was higher with ridaforolimus/dalotuzumab (any ridaforolimus dose) than with exemestane. Lowering the ridaforolimus dose reduced the incidence of grade 3 stomatitis, but overall toxicity remained higher than acceptable at all doses without improved efficacy.

CONCLUSIONS

The combination of ridaforolimus plus dalotuzumab was no more effective than exemestane in patients with advanced ER-positive breast cancer, and the incidence of adverse events was higher. Therefore, the combination is not being further pursued.

Phase I study of the combination of balixafortide (CXCR4 inhibitor) and eribulin in HER2-negative metastatic breast cancer (MBC) patients (pts)

2555

Background: Balixafortide (POL6326) is a cyclic peptide and a potent, selective antagonist of the chemokine receptor CXCR4. Evidence suggests that CXCR4 inhibition interferes with the tumor-protective microenvironment and sensitizes tumor cells to chemotherapy. The combination of balixafortide (B) and eribulin (E) was safe with early signs of efficacy in the dose escalation part of this study. Methods: The expanded cohort of thisopen label phase I study was designed to assess the anti-tumor activity, safety and pharmacokinetics of the addition of the recommended phase 2 dose (RP2D) of B to E in pts with MBC and with any CXCR4 expression level at the tumor site. Patients received E (1.4 mg/m2) on days 2 and 9, flanked by B (5.5 mg/kg) on days 1-3, and 8-10 of 21-day cycles. Results: 24 pts with relapsed MBC (median age 59 [33-82]) were enrolled in the expanded cohort. Median number of prior chemotherapies for MBC was 2 (range 1-3). 20/24 (83%) pts were ER and/or PR positive; 3/24 (13%) pts had TNBC. Objective response rate (ORR) was 33%. 8/24 (33%) pts achieved a partial response and 4/24 (17%) pts had meaningful (≥ 6 months) stable disease for a Clinical Benefit Ratio of 50%. Median duration of treatment was 15.3 weeks (range 5-40) with 11 pts still on treatment. The most common Gr 3-4 adverse events were neutropenia (9/24, 38%) and leucopenia (3/24, 13%); 2 pts had febrile neutropenia and 1 patient died from sepsis. 15/24 (63%) pts experienced histamine-like infusion reactions related to B that were manageable with anti-histamines. Conclusions: The therapeutic activity of this treatment regimen appears promising with an ORR of 33% in patients with advanced MBC. B (5.5 mg/kg) can be combined safely with E (1.4 mg/m2) and the safety profile resembles E monotherapy as previously reported. This is the first study of the treatment combination of E with B in relapsed MBC pts. Further confirmatory studies are being considered. Clinical trial information: NCT01837095.

CORALLEEN: A phase 2 clinical trial of chemotherapy or letrozole plus ribociclib as neoadjuvant treatment for postmenopausal patients with luminal B/HER2-negative breast cancer

TPS594

Background: Dysregulation of cyclin D-CDK4/6-Rb pathway is associated with endocrine resistance in hormone receptor–positive (HR+) breast cancer. Recently, a CDK4/6 inhibitor has shown unprecedented efficacy in metastatic disease, leading to its regulatory approval. Several others are currently in clinical development for the management of HR+ breast cancer in the early and advanced settings. However, it is vital to gain insights into the molecular and biological effects of this class of agents and could identify patients who can benefit the most, delaying or avoiding the use of chemotherapy.The neoadjuvant setting provides an ideal scenario to carry out these investigations. Hence, we propose to conduct an exploratory study to evaluate the biological effects and the efficacy of ribociclib in patients with primary luminal B tumors.We hypothesize that the combination of ribociclib plus letrozole may offer clinical benefit in the preoperative setting. Methods: This is a parallel, multicenter, two-arm, randomized exploratory study in postmenopausal women with primary operable HR+/HER2-negative Luminal B breast cancer designed to evaluate the clinical benefit of ribociclib plus letrozole. Eligibility includes stage I-III operable breast cancer, Luminal B by PAM50, ECOG 0-1. They will be randomized 1:1 to receive either six 28-days cycles of ribociclib (600mg; 3-weeks-on/1-week-off) plus daily letrozole (2.5mg) or chemotherapy: four cycles of AC (doxorubicin 60 mg/m2, cyclophosphamide 600 mg/m2 every 21 days) followed by weekly paclitaxel during 12 weeks. Baseline, Day 15 on-treatment, and surgical specimens will be collected for molecular characterization and evaluation of response (decrease in Ki67, change to ROR low disease) The primary endpoint is the rate of Residual Cancer Burden (RCB) per MD Anderson Cancer Center procedures. A rate of RCB 0 and 1 score at surgery, with a rank between 20% to 25% with 47 evaluable patients by group of treatment will offer a precision between 11.5% and 12.4%, respectively (95%CI). Ninety-four patients will be enrolled in 20 sites across Spain.

A phase 3 study of alpelisib (ALP) plus fulvestrant (FUL) in men and postmenopausal women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) ABC progressing on or after aromatase inhibitor (AI) therapy: SOLAR-1

TPS1111

Background: Patients (pts) with HR+ breast cancer (BC) often havedysregulatedphosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway, which further leads to resistance to endocrine therapy (ET). In a phase 1 study, alpelisib (BYL719), a PI3Kα-specific inhibitor in combination with fulvestrant (FUL) has demonstrated antitumor activity in pts with estrogen receptor-positive, HER2– advanced BC (ABC) with PIK3CA-altered tumors. SOLAR-1 (NCT02437318) aims to assess the efficacy of ALP + FUL in PIK3CA-mutant and non-mutant tumors in HR+, HER2– ABC setting. Methods: SOLAR-1 is a phase 3, randomized, double-blind study conducted in men and postmenopausal women with HR+, HER2– ABC. Pts are randomly (1:1) allocated to oral alpelisib/placebo (300 mg qd) and intramuscular FUL (500 mg) until disease progression or treatment (tx) discontinuation. Stratification factors are presence of liver and/or lung metastases and prior use of CDK4/6 inhibitors. The eligibility criteria for the targeted BC patient population are shown in the Table. The primary endpoint is progression-free survival (PFS; RECIST v1.1; local assessment), while overall survival (OS) is a key secondary endpoint in the PIK3CA-mutant cohort. Other secondary endpoints are PFS and OS in the PIK3CA non-mutant cohort, the association between PFS and baseline PIK3CAstatus in ctDNA, overall response rate, clinical benefit rate, and safety. Recruitment of the planned 560 pts is currently ongoing. Clinical trial information: NCT02437318. [Table: see text]

Abstract OT2-01-04: SOLAR-1: A phase III study of alpelisib and fulvestrant in men and postmenopausal women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) advanced breast cancer (BC) progressing on or after aromatase inhibitor (AI) therapy

Background: The phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway is often dysregulated in HR+ BC and is associated with resistance to endocrine therapy (ET). Alpelisib (BYL719; PI3Kα-specific inhibitor) and fulvestrant showed signs of antitumor activity in patients (pts) with estrogen receptor-positive (ER+), HER2– advanced BC (phase I), especially in PIK3CA-altered tumors (Janku et al. SABCS 2014, PD5-5).

Methods: SOLAR-1 (NCT02437318) is a phase III, randomized, double-blind study in men and postmenopausal women with HR+, HER2– advanced BC. Pts are assigned to 1 of 2 cohorts based on PIK3CA tumor status (mutant vs non-mutant), and randomized 1:1 to oral alpelisib/placebo (300 mg once daily) and intramuscular fulvestrant (500 mg on Day 1 and 15 of Cycle 1; Day 1 of Cycles ≥2 [28-day cycles]) until disease progression or discontinuation. Randomization is stratified by presence of liver and/or lung metastases and prior CDK4/6 inhibitor therapy. Key inclusion criteria: recurrence or progression on or after AI therapy, ≥1 measurable lesion (RECIST v1.1) or predominantly lytic bone lesion, and ECOG performance status ≤1. Key exclusion criteria: symptomatic visceral disease or disease burden precluding ET, acute pancreatitis ≤1 year prior to screening or history of chronic pancreatitis, and prior therapy with fulvestrant, chemotherapy (except [neo]adjuvant), or PI3K/AKT/mTOR inhibitors.

The primary and key secondary endpoints are progression-free survival (PFS; RECIST v1.1; local assessment) and overall survival (OS), respectively, in the PIK3CA-mutant cohort. Other secondary endpoints include PFS and OS in the PIK3CA non-mutant cohort, PFS (Blinded Independent Central Review; RECIST v1.1), the association between PFS and baseline PIK3CA status in circulating tumor DNA, overall response rate, clinical benefit rate, safety, and pharmacokinetics. The primary endpoint will be analyzed by a stratified log-rank test at one-sided 2% level of significance.

Recruitment of the planned 560 pts is ongoing.

Citation Format: Andre F, Kaufman B, Juric D, Ciruelos EM, Iwata H, Mayer IA, Rugo HS, Conte P, Liobl S, Rubovszky G, Inoue K, Tesch H, Lu Y-S, Ryvo L, Longin A-S, Mills D, Wilke C, Germa C, Campone M. SOLAR-1: A phase III study of alpelisib and fulvestrant in men and postmenopausal women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) advanced breast cancer (BC) progressing on or after aromatase inhibitor (AI) therapy [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr OT2-01-04.

Abstract P4-07-09: Differential expression of microRNAs (miRNAs) in HER2 negative breast cancer (BC)

Background:

MiRNAs are non-coding single-stranded RNAs that control gene expression by directing their target mRNAs for degradation and/or posttranscriptional repression. Compared to mRNA signatures, miRNAs have better and stronger biomarker properties with 20 times more power in biomarker studies as compared to mRNAs (when comparing 20,000 mRNAs to ~ 1,000 miRNAs). Global downregulation of miRNAs has emerged as a common theme in human breast tumors and has been shown to contribute to oncogenesis

Hormone receptor (HR) status is one of the most important factors influencing BC outcome. Several data indicate the extensive alterations in miRNAs regulation upon estrogen pathway and suggest the utility of considering miRNAs expression in the understanding the development of cancer disease, invasiveness, metastasis and treatment failure.

Our aim was to identify differential expression miRNAs in HER2 negative BC. We previously reported a set of miRNAs deregulated in HR+/HER2- BC vs. Triple negative BC (TNBC). In this work we have validate these differences in a new cohort of BC patients.

Methods:

Total RNA was extracted samples extracted from primary breast cancer FFPE tissue. MicroRNAs expression was analyzed by RT-qPCR using TaqMan Arrays from Applied Biosystems. Normalization was performed using de DCt method with two housekeeping miRNAs identified previously identified using NorMean. MicroRNA expression values in each group were compared by the Mann Whitney test.

Results:

121 patients with early HER2 negative BC were included in the present study. All patients showed absence of nodal involvement at the time of diagnosis. The median age at diagnosis was 56 years, 89 cases (74%) had positive estrogen receptor and 53 cases (44%) grade 3. miR-20a, miR-19a, miR-106a, miR-18a and miR-135b expression were significantly higher in TNBC samples, whereas miR-190b, miR-375, miR-449a, miR-342, miR-149, miR-193b, miR-214, miR-30a*and miR-30e* were significantly more expressed in ER+/HER2- samples. No significant differences were found in miR-139-5p expression between both groups.

Conclusions:

We have validated fourteen miRNAs that are differentially expressed between ER+/HER2- and TNBC breast cancer subtypes. Altered expression of miRNAs could be a potential therapeutic tool and promising biomarker in personalized treatment.

Citation Format: Pascual T, Gámez-Pozo A, Camara-Jurado M, Manso LM, Pérez-Campos A, Trilla L, Fresno-Vara JA, Ciruelos EM. Differential expression of microRNAs (miRNAs) in HER2 negative breast cancer (BC) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-07-09.

Abstract P4-21-16: Phase III trial to evaluate patient´s preference for subcutaneous versus intravenous trastuzumab administration in patients with HER2 positive advanced breast cancer (ABC) under IV trastuzumab (IV-t) treatment for at least 4 months. ChangHER-SC study (GEICAM/2012-07)

Background: Patients with HER2-positive ABC, receive anti-HER2 treatment for several months or even years. IV-t is administered weekly or 3-weekly, mandating patients to visit the hospital on a regular basis to receive infusions. This has inconveniences for patients and increase treatment costs. Subcutaneous administration could improve convenience of trastuzumab therapy. This study was designed to evaluate patient's preference for IV-t or SC trastuzumab (SC-t) in ABC patients.

Methods:This is a phase III, open label, multicenter study inpatients with HER2 positive ABC, receiving IV-t for at least 4 months and without evidence of disease progression. Patients received 600 mg of SC-t, either from a vial or from a single injection device (SID), every 3 weeks for 4 cycles. Before starting SC-t, patients received an additional IV-t cycle. Patients were randomized 1:1 to arm A, receiving 2 cycles of SC-t with vial followed by 2 cycles with SID or arm B, receiving the opposite sequence. After cycle 4, patients decided to continue with IV-t or SC-t till disease progression. Stratification criteria were the associated therapy (Chemotherapy, Hormone-therapy or none) and its administration route (IV, oral or none). Patients completed a questionnaire of experiences and preferences at three time points: before starting SC-t, after cycle 2 and after cycle 4. Health Care Professionals completed a satisfaction questionnaire every 5 patients. The primary objective was to evaluate patient´s preference for IV-t or SC-t (after cycle 2) and, secondary objectives were, to evaluate patient´s preference between the two SC-t administrations (vial or SID) after cycle 4, Health Care Professional satisfaction, associated costs of the administration options (Time and Motion pharmacoeconomic study) and safety.

Results: From September-13 to July-15, 166 patients were randomized (81 arm A, 85 arm B) in 26 Spanish sites from GEICAM. Median age was 60 years (35-93), 88% of patients were postmenopausal and 123 and 42 had an ECOG PS of 0 and 1, respectively. The median duration of prior IV-t for ABC was 1.8 years (range: 0.3-14). Patients received a median of 2 previous lines of Chemotherapy and/or Hormone-therapy (range: 1-9). Twenty patients were receiving pertuzumab at inclusion. According to patient questionnaires completed after cycle 2, 137 patients preferred the SC-t (66 arm A, 71 arm B), 11 the IV-t (6 arm A, 5 arm B), 11 didn't have a preference (4 arm A, 7 arm B), and 7 didn't answer (3 progressed, 2 withdrew participation before cycle 2 and 2 unknown reason). Three of the 11 patients choosing IV-t were receiving IV treatment as accompanying therapy; after cycle 4 five of these 11 patients finally continued with SC-t, 5 with IV-t and 1 progressed. From the 11 patients without any preference 7 received SC-t, 2 receive IV-t and 2 progressed; from the 137 patients preferring SC-t, 125 actually received it, 3 received IV-t and 9 progressed.

Conclusions: Our study shows that 82.5% of patients preferred the SC-t over the IV-t. Treatment choice was not influenced by the accompanying therapy.

Citation Format: Ciruelos EM, Montaño Á, Rodríguez CA, González-Flores E, Lluch A, Garrigós L, Quiroga V, Antón A, Malón D, Chacón JI, Velasco M, Gonzalez-Cortijo L, Jolis L, Pascual T, Amigo Y, Casas M, Cámara MC, Carrasco E, Casas A. Phase III trial to evaluate patient´s preference for subcutaneous versus intravenous trastuzumab administration in patients with HER2 positive advanced breast cancer (ABC) under IV trastuzumab (IV-t) treatment for at least 4 months. ChangHER-SC study (GEICAM/2012-07) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-21-16.

Safety of everolimus plus exemestane in patients with hormone-receptor-positive, HER2-negative locally advanced or metastatic breast cancer progressing on prior non-steroidal aromatase inhibitors: primary results of a phase IIIb, open-label, single-arm, expanded-access multicenter trial (BALLET)

BACKGROUND

This European phase IIIb, expanded-access multicenter trial evaluated the safety of EVE plus EXE in a patient population similar to BOLERO-2.

PATIENTS AND METHODS

Post-menopausal women aged ≥18 years with hormone receptor-positive, human epidermal growth factor-receptor-2-negative advanced breast cancer (ABC) recurring/progressing during/after prior non-steroidal aromatase inhibitors were enrolled. The primary objective was safety of EVE plus EXE based on frequency of adverse events (AEs), and serious AEs (SAEs). The secondary objective was to evaluate AEs of grade 3/4 severity.

RESULTS

The median treatment duration was 5.1 months [95% confidence interval (CI) 4.8-5.6] for EVE and 5.3 months (95% CI 4.8-5.6) for EXE. Overall, 2131 patients were included in the analysis; 81.8% of patients experienced EVE- or EXE-related or EVE/EXE-related AEs (investigator assessed); 27.2% were of grade 3/4 severity. The most frequently reported non-hematologic AEs were (overall %, % EVE-related) stomatitis (52.8%; 50.8%) and asthenia (22.8%; 14.6%). The most frequently reported hematologic AEs were (overall %, % EVE-related) anemia (14.4%; 8.1%) and thrombocytopenia (5.9%; 4.6%). AE-related treatment discontinuations were higher in elderly (≥70 years) versus non-elderly patients (23.8% versus 13.0%). The incidence of EVE-related AEs in both elderly and non-elderly patients appeared to be lower in first-line ABC versus later lines. The incidence of AEs (including stomatitis/pneumonitis) was independent of BMI status (post hoc analysis). Overall, 8.5% of patients experienced at least one EVE-related SAE. Of the 121 on-treatment deaths (5.7%), 66 (3.1%) deaths were due to disease progression and 46 (2.2%) due to AEs; 4 deaths were suspected to be EVE-related.

CONCLUSIONS

This is the largest ever reported safety dataset on a general patient population presenting ABC treated with EVE plus EXE and included a sizeable elderly subset. Although the patients were more heavily pretreated, the safety profile of EVE plus EXE in BALLET was consistent with BOLERO-2.

CLINICAL TRIAL REGISTRATION

EudraCT Number: 2012-000073-23.

Abstract P4-13-10: Stomatitis following everolimus (EVE) plus exemestane (EXE) in patients with hormone receptor-positive (HR+), HER2– advanced breast cancer (ABC) in the BALLET trial (CRAD001YIC04)

Background

Stomatitis is the most common adverse event (AE) associated with mTOR inhibitors, including EVE. In the pivotal BOLERO-2 trial, stomatitis was reported for 59% vs 12% (Gr3, 8% vs &lt;1%) of pts with HR+, HER2– ABC who received EVE + EXE vs EXE alone. Of the limited real world evidence available, the BRAWO trial showed a stomatitis incidence of 39.8% (Gr3, 3.4%) in a similar pt population. Additional data are warranted to better understand the stomatitis incidence and time-course in order to minimize treatment discontinuations.

Methods

BALLET is a Phase 3b, European, multi-center, open-label, single-arm, expanded-access study that evaluated safety of EVE (10 mg/d) and EXE (25 mg/d) in 2131 postmenopausal women with HR+, HER2– ABC that progressed on prior NSAI treatment. Primary endpoint was safety; secondary endpoint was characterization of grade 3/4 AEs. In this exploratory analysis, we split the pts in two groups based on having experienced at least one all grade stomatitis event in the first 8 wks (cut-off chosen based on reports that 89.4% of stomatitis events occurred within 8 wks of EVE initiation [Rugo, ASCO 2014]) vs none.

Results

This subgroup analysis included 919 pts with stomatitis (43.1% of the full population). Baseline pt characteristics were comparable to the overall study population, except for more comorbidity (cardiovascular and metabolic disorder) in stomatitis subset. Pts with stomatitis had a longer EVE treatment duration vs pts who didn't (5.8 mo [95%CI, 5.0-6.2] vs 4.7 mo [95%CI, 4.4-5.3]; hazard ratio, 1.121 [95%CI, 0.97-1.28] censored by pts who switched to commercial drug). The relative risk of initial onset of stomatitis at 6 wks was ∼40%; median time to onset was 28 days. Majority of stomatitis events were of grade 1/2 severity (80%); grade 3/4 stomatitis was reported for 20% of pts. Most frequent reasons for treatment discontinuation in pts with stomatitis were reimbursement (37.6%), disease progression (35.0%), and AEs (16.2%). Most frequent AEs which led to treatment discontinuation in these pts were stomatitis in 3.7% (Grade 3/4, 2%), pneumonitis in 2.9% (Grade 3/4, 1.3%) and asthenia in 1.8% (Grade 3/4, 1%). Median EVE relative dose intensity in pts with stomatitis was 0.92. In the stomatitis subset, dose interruptions and reductions were required for 66.7% and 37.6% of pts, respectively; most frequent reasons for dose adjustments were AEs (65.9%) which included stomatitis (46.8%), asthenia (6.3%), and pneumonitis (5.3%). Median time to first dose modification in pts with stomatitis was 30 days; median duration of dose interruptions was 16 days. On-treatment deaths (4.4%) were due to progressive disease (2.1%), AEs (1.7%), and other reasons (0.5%).

Conclusions

These results confirmed the stomatitis time-course observed previously and that the majority of these events are of low grade. Stomatitis was the most common cause of dose reductions and interruptions due to AEs and was manageable with dose adjustments; there was a positive association between stomatitis and longer treatment duration. Therefore, proactive management, diligent monitoring and appropriate dose modifications, are recommended to keep pts on treatment.

Citation Format: Ciruelos EM, Jerusalem G, Generali D, Lang I, Gavila JG, Michelotti A, Tjan-Heijnn VCG, Mariani G, Conte P, Beliera A, Camozzi M, Lorizzo K, Martin M. Stomatitis following everolimus (EVE) plus exemestane (EXE) in patients with hormone receptor-positive (HR+), HER2– advanced breast cancer (ABC) in the BALLET trial (CRAD001YIC04). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-10.

Abstract P3-07-40: Pharmacogenetic study of exemestane and everolimus in metastatic breast cancer patients progressing on prior non-steroidal aromatase inhibitors

Background: Activation of the mTOR pathway has been observed in patients (pts) with metastatic breast cancer (MBC) progressing on endocrine therapy. BOLERO-2 trial demonstrated a significant increase in progression free survival (PFS) obtained with everolimus (EVE) and exemestane (EXE) versus EXE alone in pts refractory to a prior non-steroidal aromatase inhibitors (NSAI). However, there is large interindividual variability in toxicity and efficacy profiles of EXE-EVE treatment. Single Nucleotide Polymorphisms (SNPs) have been proposed to explain some of these differences. The objective of this study was to perform a pharmacogenetic analysis to identify SNPs associated with EVE toxicity and activity.

Methods: This is a prospective unicentric clinical trial for postmenopausal pts with hormone receptor-positive, HER2 negative, MBC progressing on prior NSAI, treated with EXE-EVE.

Blood samples were obtained from all pts, and 12 SNPs in key genes involved in EXE pharmacokinetics (ABCB1, CYP2C8, CYP3A4, CYP3A5) and pharmacodynamics (AKT1, AKT2, FGFR4, PHLPP2, PIK3R1, RAPTOR) were genotyped. EVE pharmacokinetics data was available for a subset of 37 pts. The association between the SNPs and EVE pharmacokinetic parameters were analyzed using U-Mann-Whitney test. A selection of clinically relevant toxicities (non-infectious pneumonitis (NIP), mucositis, hyperglycemia and hematological) was analyzed using binary logistic regression. Cox regression was used to analyze the association of SNPs with time to treatment modifications (reduction or interruption) due to toxicity, PFS and OS.

Results: 90 patients with median age of 62 yrs were included. At data cut off, a total of 77 pts had discontinued treatment. Major reasons for discontinuation were: disease progression (80%), adverse events (17%) and death (2%). Number of prior chemotherapy lines: 0; 50%, 1;18%, 2;10%, ≥3; 22%. 76% of pts experienced at least one adverse event related to EVE.

CYP3A4 rs35599367 (CYP3A4*22 allele) heterozygous pts had higher EVE concentration in blood compared to wild type pts (P=0.019), in agreement with previous data.

Regarding EVE toxicities, ABCB1 SNP rs1045642 showed a higher risk of mucositis (HR=2.3, 95%CI=1.1-4.8, P=0.031; multivariable analysis), and PIK3R1 rs10515074 variant was inversely associated with hyperglycemia (HR=0.24, 95%CI=0.1-0.8, P=0.016; multivariable analysis). RAPTOR rs9906827 protected for NIP (HR=0.38, 95%CI=0.2-0.9, P=0.024; multivariable analysis). When analyzing the time to treatment modification due to any toxicity, we observed a trend for FGFR4 rs351855 and RAPTOR rs9906827 (HR=0.59, 95%CI=0.3-1.0, P=0.06 and HR=0.71, 95%CI=0.5-1.1, P=0.12; respectively, in multivariable analysis).

Regarding activity, RAPTOR rs9906827 was also associated with longer PFS (dominant model HR=0.48, 95%CI=0.3-0.8, P=0.006; multivariable analysis). No SNP was significantly associated with OS.

Conclusions: We found altered EVE pharmacokinetics for CYP3A4*22 carriers and protection for NIP and longer PFS for RAPTOR rs9906827. This study supports prospective trials for genetic testing prior to EXE-EVE therapy to stratify patients according to toxicity and efficacy risk profiles.

Citation Format: Pascual-Martínez T, Apellániz-Ruiz M, Pernaut C, Cueto-Felgueroso C, Villalba P, Alvarez C, Manso L, Rodriguez-Antona C, Ciruelos EM. Pharmacogenetic study of exemestane and everolimus in metastatic breast cancer patients progressing on prior non-steroidal aromatase inhibitors. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-07-40.

Abstract P5-19-02: Everolimus in combination with exemestane in hormone receptor-positive locally advanced or metastatic breast cancer (BC) patients progressing on prior non-steroidal AI (NSAIs): Ballet study (CRAD001YIC04)

Background:

Despite progress, a large number of breast cancer patients experience metastatic relapse and death.

Hyperactivation of the mTOR pathway has been observed in patients (pts) with BC progressing on endocrine therapy. The BOLERO-2* trial demonstrated significant doubling of PFS obtained via dual blockade with everolimus (EVE) and exemestane (EXE), versus EXE alone in pts refractory to NSAIs.

Methods:

BALLET is a European multi-center open-label, single-arm, expanded-access study to evaluate the safety of EVE (10 mg/day) and EXE (25 mg/day) in postmenopausal women with hormone receptor-positive HER2 negative locally advanced or metastatic BC progressing on prior NSAIs. Study treatment continued until disease progression, unacceptable toxicity, death, drug locally reimbursed, discontinuation from the study for any other reason or last patient last visit (June 30th, 2014), whichever occurred first. Here we report an ad hoc-analysis that includes all pts recruited from May 12th 2012 till Dec 31st 2013 with cut-off date March 17th 2014 (final database will be available on October 31st 2014).

Results:

2.133 pts were recruited in 269 sites across 14 European countries. Baseline characteristics were median age: 64 yrs; PS (ECOG) 0/1/2: 64%/30%/3%; median time from first diagnosis: 8 yrs; Stage IV pts: 99%. At the data cut off, a total of 1795 pts (84%) had discontinued the treatment. Reasons for discontinuation were: disease progression (38%), drug reimbursement (35%), adverse events (15 %), consent withdrawn (4%), death (1.5%) and others (6.5%). EVE and EXE were administered as first line treatment in 10% of pts, as second line in 23%, as third line in 22% and as fourth line or beyond in 45% of pts. 74% of pts received more than 1 line of chemotherapy in the metastatic setting. 80% of pts experienced at least one adverse event (AE) referred by the investigators as related to EVE [45% stomatitis, 7% non-infectious pneumonitis (NIP)]. The most frequent grade 3-4 drug related AEs were stomatitis (8.9%), asthenia (3.2%), GGT increase (2.4%), hyperglycemia (2.4%), and NIP (1.8%).The median time to onset of stomatitis and NIP was 3-4 weeks and 2-3 months respectively.

Conclusions:

These results confirm that the combination of EVE + EXE is a tolerable treatment in a real world setting even in pts more heavily pretreated by chemotherapy compared to BOLERO 2. The better understanding of side effects leading to treatment discontinuation in this large European study where investigators frequently administered the drug for the first time, will allow defining priority actions for better management of side effects including patient education and early interventions.

Longer follow up with mature data (expected in October 2014) will give additional information on the safety profile, stratified by line of treatment.

* Everolimus in Postmenopausal Hormone- Receptor–Positive Advanced Breast Cancer. J. Baselga et al, NEJM 2012.

Citation Format: Guy Jerusalem, Gabriella Mariani, Eva M Ciruelos, Miguel Martin, Vivianne CG Tjan-Heijnen, Patrick Neven, Joaquin Gavila Gregori, Andrea Michelotti, Filippo Montemurro, Istvan Lang, Josef Mardiak, Bjoem Naume, Maura Camozzi, Katia Lorizzo, Dariusz Brenski, Pierfranco Conte. Everolimus in combination with exemestane in hormone receptor-positive locally advanced or metastatic breast cancer (BC) patients progressing on prior non-steroidal AI (NSAIs): Ballet study (CRAD001YIC04) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-19-02.

Abstract S3-08: Randomized comparison of adjuvant tamoxifen (T) plus ovarian function suppression (OFS) versus tamoxifen in premenopausal women with hormone receptor-positive (HR+) early breast cancer (BC): Analysis of the SOFT trial

Background It is uncertain if the addition of OFS to adjuvant endocrine therapy with T improves outcomes in premenopausal HR+ BC. The SOFT trial was designed to determine the value of OFS in women who remain premenopausal and are treated with T (OFS question) and also to test whether an AI improves outcome in premenopausal women with HR+ BC treated with OFS (AI question). In the combined analysis of the TEXT and SOFT trials (AI question), the group treated with the AI exemestane+OFS had a significantly better disease-free survival (DFS) than those with T+OFS. This abstract presents the results of the OFS question (n=2,045).

Patients and Methods Between November 2003 and January 2011, the SOFT phase 3 trial randomized 3066 premenopausal women with HR+ BC to 5 years of adjuvant endocrine therapy with exemestane+OFS versus T+OFS versus T alone, with OFS initiated by choice of GnRH agonist triptorelin, oophorectomy or ovarian irradiation. Prior chemotherapy was allowed, provided women had confirmed premenopausal estradiol levels within 8 months of completing chemotherapy. The primary end point was DFS which included invasive local, regional, distant and contralateral breast events, second non-breast malignancies and deaths without prior cancer. Because of a lower-than expected overall event rate and to ensure results within a reasonable time-frame, a protocol amendment in 2011 changed the originally event-driven analysis plan. The amendment (1) designated the comparison of T+OFS versus T alone as the primary analysis for SOFT (n=2045), recognizing that the statistical power for the original three pairwise comparisons would be substantially reduced and (2) specified that the primary analysis of T+OFS versus T be undertaken when median follow-up was at least 5 years. The comparison would be tested at the 2-sided 0.05 level with no interim analysis. Based on the projected number of events at the lower rates, the estimated power to detect hazard ratios of 0.75, 0.70, and 0.66 for the comparison would be 52%, 69%, and 80%.

Results The SOFT trial completed planned patient enrollment with an international collaboration involving 426 centres from BIG and NABCG led by the International Breast Cancer Study Group (IBCSG). Numbers of patients randomized, randomization strata, and pt age are summarized in the Table. The database lock for the primary analysis of the OFS question will occur in September 2014 and the final analysis will be completed by October 15, 2014.

SOFT Patients (%)Tamoxifen alone1021 (33%)Tamoxifen+OFS1024 (33%)Exemestane+OFS1021 (33%)*  Prior Chemotherapy54%Lymph node positive35%Median age (% &lt; 40 years)43 years (30%)*Patients randomized to Exemestane+OFS are not part of the current analysis

Conclusions We will present the primary analysis of outcomes and toxicities by treatment for women randomized to receive T+OFS versus T and address the value of OFS in addition to T as adjuvant endocrine therapy for premenopausal women with HR+ BC.

Citation Format: Aron Goldhirsch, Richard D Gelber, Prudence A Francis, Meredith M Regan, Gini F Fleming, Istvan Lang, Eva M Ciruelos, Meritxell Bellet, Herve Bonnefoi, Miguel A Climent, Lorenzo Pavesi, Harold J Burstein, Silvana Martino, Nancy E Davidson, Charles E Geyer Jr, Barbara A Walley, Robert E Coleman, Pierre Kerbrat, Manuela Rabaglio-Poretti, Alan S Coates. Randomized comparison of adjuvant tamoxifen (T) plus ovarian function suppression (OFS) versus tamoxifen in premenopausal women with hormone receptor-positive (HR+) early breast cancer (BC): Analysis of the SOFT trial [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr S3-08.

The Long-HER study: clinical and molecular analysis of patients with HER2+ advanced breast cancer who become long-term survivors with trastuzumab-based therapy

Background

Trastuzumab improves survival outcomes in patients with HER2+ metastatic breast cancer. The Long-Her study was designed to identify clinical and molecular markers that could differentiate long-term survivors from patients having early progression after trastuzumab treatment.

Methods

Data were collected from women with HER2-positive metastatic breast cancer treated with trastuzumab that experienced a response or stable disease during at least 3 years. Patients having a progression in the first year of therapy with trastuzumab were used as a control. Genes related with trastuzumab resistance were identified and investigated for network and gene functional interrelation. Models predicting poor response to trastuzumab were constructed and evaluated. Finally, a mutational status analysis of selected genes was performed in HER2 positive breast cancer samples.

Results

103 patients were registered in the Long-HER study, of whom 71 had obtained a durable complete response. Median age was 58 years. Metastatic disease was diagnosed after a median of 24.7 months since primary diagnosis. Metastases were present in the liver (25%), lungs (25%), bones (23%) and soft tissues (23%), with 20% of patients having multiple locations of metastases. Median duration of response was 55 months. The molecular analysis included 35 patients from the group with complete response and 18 patients in a control poor-response group. Absence of trastuzumab as part of adjuvant therapy was the only clinical factor associated with long-term survival. Gene ontology analysis demonstrated that PI3K pathway was associated with poor response to trastuzumab-based therapy: tumours in the control group usually had four or five alterations in this pathway, whereas tumours in the Long-HER group had two alterations at most.

Conclusions

Trastuzumab may provide a substantial long-term survival benefit in a selected group of patients. Whole genome expression analysis comparing long-term survivors vs. a control group predicted early progression after trastuzumab-based therapy. Multiple alterations in genes related to the PI3K-mTOR pathway seem to be required to confer resistance to this therapy.

Abstract P2-16-04: A phase 2 study of ridaforolimus (RIDA) and dalotuzumab (DALO) in estrogen receptor positive (ER+) breast cancer

Background: Preclinical studies indicate that the dual inhibition of IGFR and mTOR may be additive or synergistic and abrogates the feedback activation of AKT due to rapamycin analog mTOR inhibitors. A phase 1 study of the mTOR inhibitor RIDA and the anti-IGFR antibody DALO demonstrated that the combination was feasible and well-tolerated at doses that were nearly those used for the two single agents. The dose limiting toxicity was stomatitis, similar to RIDA monotherapy. Preliminary signals of anti-tumor activity, including partial responses and prolonged progression free survival (PFS), were observed in ER+ advanced breast cancer (ABC), especially in high proliferation tumors (Ki67 ≥15%). Methods: The trial was a multi-center, international randomized study with PFS as the primary endpoint. Key eligibility included ABC with prior treatment with a non-steroidal aromatase inhibitor. The original phase 2 study design was a two-part, adaptive design intended to first test the combination of RIDA (30 mg by mouth daily for 5 out of every 7 days), -DALO (10 mg/kg IV weekly) against a standard agent, exemestane in Part A. Patients were stratified into high and low proliferation strata based on baseline Ki67. Following a demonstration of PFS benefit of the combination in Part A, Part B was intended to show the PFS benefit of the combination over each single agents by comparing RIDA-DALO to RIDA and DALO. Results: The study was initiated in October 2011. Accrual was suspended after the first 66 patients were randomized due to a higher than expected rate of stomatitis in the RIDA-DALO arm. Preliminary data indicated an overall incidence of any grade stomatitis was 68% (22/33 pts), and of grade 3 stomatitis was 35% (11/33 pts). In an effort to identify a more tolerable regimen, the study was amended to eliminate Part B and to evaluate two sequential reduced dose RIDA-DALO cohorts in a non-randomized design: 20mg and 10mg for 5 out of every 7 days. The dose of DALO was unchanged. Preliminary safety results of overall and grade 3 stomatitis in the 20 mg were 81.5% (22/27 pts) and 37% (10/27 pts), respectively. Although the incidence of overall stomatitis in the 10 mg cohort remained high, 88% (22/25 pts), grade 3 stomatitis was dramatically reduced to 8% (2/25 pts). Conclusion: Preliminary evaluation of safety from this phase 2 study demonstrates that the previously recommended phase 2 dose of RIDA-DALO was not tolerable. However lower doses of RIDA (10 mg) in combination with DALO appeared to be tolerable with markedly reduced rates of grade 3 stomatitis. Final results of efficacy, safety and RNA profiling analysis from the two RIDA-DALO dose cohorts as well as from the randomized portion of the study will be available at the time of the meeting.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-16-04.

Lapatinib with trastuzumab for heavily treated HER2-positive metastatic breast cancer (mBC)

e11561

Background: Trastuzumab and lapatinib show complementary and non-cross resistant mechanisms of anti-HER2 action. Dual HER2 blockade has been preclinically and clinically assessed with encouraging results. Trastuzumab and lapatinib combination is effective in terms of survival in patients with heavily pretreated HER2-positive mBC. We aim to report our experience with lapatinib plus trastuzumab in this setting. Methods: Descriptive retrospective study of trastuzumab plus lapatinib activity in patients with HER2-overexpressing metastatic breast cancer treated in two institutions from 01/2007 to 12/2012. The objective of this analysis is to report the response rate (RR), progression-free survival (PFS) and toxicity. Results: 23 HER2-positive mBC patients previously treated with trastuzumab received trastuzumab plus lapatinib based therapy. 15 patients (65%) received 2 or more previous lines. 17 patients (74%) had visceral disease. Chemotherapy (CT) was added to the dual HER2 blockade treatment in 13 patients (56%) whereas hormonotherapy (HT) was added in 8 patients (35%) and 2 patients (9%) received lapatinib plus trastuzumab without any other agent. Chemotherapeutic drugs most used were: capecitabine (54%) and vinorelbine (15%). RR: partial response 22% (5/23), stable disease 39% (9/23). Median of follow-up was 11 months. PFS in the overall population was 4 months. PFS in patients with CT was 5 months, while PFS in patients with HT was only 2. PFS in hormone receptor positive and negative was 3 and 5 months respectively. The most common toxicities were: diarrhea (48%), anemia (39%), asthenia (39%) and hand-and-foot syndrome (17%). Grade ≥ 3 toxicity was diarrhea (26%) and hand-and-foot syndrome (9%). The incidence of cardiotoxicity was 9% (grade 2). Conclusions: These findings suggest that dual HER2 blockade in combination with CT is feasible and active in heavily pretreated HER2-positive mBC patients. However, further investigation is warranted to demonstrate superiority over sequential blockade with trastuzumab and lapatinib in this setting.

Abstract P5-10-11: Clinical significance of microRNA expression as a prognostic factor in early N+ breast cancer (BC)

Background: microRNAs (miRNAs) are small noncoding RNA molecules that post-transcriptionally regulate gene expression. In the present study, we describe miRNA expression in early node-positive BC and identify a 8-miRNA score that could contribute to prognosis assessment.

Methods: First, microarray analysis was performed using RNA samples extracted from primary breast cancer. The expression of miRNAs was analyzed by RT-qPCR using the TaqMan Arrays from Applied Biosystems. After a suitable normalization of the 677 miRNAs analyzed, 123 presented a good correlation between their levels of expression in frozen tissue and paraffin tissue. A supervised analysis was done in order to identify MIR that could predict relapse.

Results: 172 patients with node-positive chemotherapy-treated early BC were included in the present study. The median age at diagnosis was (53.7) years, 128 cases (74.4%) had positive estrogen receptor, and 163 patients (94,7%) received adjuvant chemotherapy. After a median follow up of 8,1 years, 71p (41.2%) relapsed. Supervised analyses identified 8 microRNAs (has miR-30e, miR-30a, miR-21, miR-210, miR-93, miR-150, miR-99b, miR-572) associated with higher risk of relapse (5 year PFS 50% vs 90%, HR 3.75, 95% CI 2.27–6.19) and with estimated overall survival (median not reached, HR 4.51, 95% CI 2.36–8.61). Interestingly, miRNAs defined 2 prognostic groups (high and low risk) regardless of type of adjuvant chemotherapy (with or without anthracyclines) and histological subtype (luminal A, B or triple negative).