Neratinib + fulvestrant + trastuzumab for HR-positive, HER2-negative, HER2-mutant metastatic breast cancer: outcomes and biomarker analysis from the SUMMIT trial

BACKGROUND

HER2 mutations are targetable alterations in patients with hormone receptor-positive (HR+) metastatic breast cancer (MBC). In the SUMMIT basket study, patients with HER2-mutant MBC received neratinib monotherapy, neratinib + fulvestrant, or neratinib + fulvestrant + trastuzumab (N + F + T). We report results from 71 patients with HR+, HER2-mutant MBC, including 21 (seven in each arm) from a randomized substudy of fulvestrant versus fulvestrant + trastuzumab (F + T) versus N + F + T.

PATIENTS AND METHODS

Patients with HR+ HER2-negative MBC with activating HER2 mutation(s) and prior cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) therapy received N + F + T (oral neratinib 240 mg/day with loperamide prophylaxis, intramuscular fulvestrant 500 mg on days 1, 15, and 29 of cycle 1 then q4w, intravenous trastuzumab 8 mg/kg then 6 mg/kg q3w) or F + T or fulvestrant alone. Those whose disease progressed on F + T or fulvestrant could cross-over to N + F + T. Efficacy endpoints included investigator-assessed objective response rate (ORR), clinical benefit rate (RECIST v1.1), duration of response, and progression-free survival (PFS). Plasma and/or formalin-fixed paraffin-embedded tissue samples were collected at baseline; plasma was collected during and at end of treatment. Extracted DNA was analyzed by next-generation sequencing.

RESULTS

ORR for 57 N + F + T-treated patients was 39% [95% confidence interval (CI) 26% to 52%); median PFS was 8.3 months (95% CI 6.0-15.1 months). No responses occurred in fulvestrant- or F + T-treated patients; responses in patients crossing over to N + F + T supported the requirement for neratinib in the triplet. Responses were observed in patients with ductal and lobular histology, 1 or ≥1 HER2 mutations, and co-occurring HER3 mutations. Longitudinal circulating tumor DNA sequencing revealed acquisition of additional HER2 alterations, and mutations in genes including PIK3CA, enabling further precision targeting and possible re-response.

CONCLUSIONS

The benefit of N + F + T for HR+ HER2-mutant MBC after progression on CDK4/6is is clinically meaningful and, based on this study, N + F + T has been included in the National Comprehensive Cancer Network treatment guidelines. SUMMIT has improved our understanding of the translational implications of targeting HER2 mutations with neratinib-based therapy.

The role of infiltrating lymphocytes in the neo-adjuvant treatment of women with HER2-positive breast cancer

Background

Pre-treatment tumour-associated lymphocytes (TILs) and stromal lymphocytes (SLs) are independent predictive markers of future pathological complete response (pCR) in HER2-positive breast cancer. Whilst studies have correlated baseline lymphocyte levels with subsequent pCR, few have studied the impact of neoadjuvant therapy on the immune environment.

Methods

We performed TIL analysis and T-cell analysis by IHC on the pretreatment and ‘On-treatment’ samples from patients recruited on the Phase-II TCHL (NCT01485926) clinical trial. Data were analysed using the Wilcoxon signed-rank test and the Spearman rank correlation.

Results

In our sample cohort (n = 66), patients who achieved a pCR at surgery, post-chemotherapy, had significantly higher counts of TILs (p = 0.05) but not SLs (p = 0.08) in their pre-treatment tumour samples. Patients who achieved a subsequent pCR after completing neo-adjuvant chemotherapy had significantly higher SLs (p = 9.09 × 10^–3) but not TILs (p = 0.1) in their ‘On-treatment’ tumour biopsies. In a small cohort of samples (n = 16), infiltrating lymphocyte counts increased after 1 cycle of neo-adjuvant chemotherapy only in those tumours of patients who did not achieve a subsequent pCR. Finally, reduced CD3 + (p = 0.04, rho = 0.60) and CD4 + (p = 0.01, rho = 0.72) T-cell counts in 'On-treatment' biopsies were associated with decreased residual tumour content post-1 cycle of treatment; the latter being significantly associated with increased likelihood of subsequent pCR (p < 0.01).

Conclusions

The immune system may be ‘primed’ prior to neoadjuvant treatment in those patients who subsequently achieve a pCR. In those patients who achieve a pCR, their immune response may return to baseline after only 1 cycle of treatment. However, in those who did not achieve a pCR, neo-adjuvant treatment may stimulate lymphocyte influx into the tumour.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10549-021-06244-1.

Abstract P5-03-02: Pre-clinical investigation of PP2A inhibitor LB-100 in overcoming and preventing lapatinib resistance in HER2-positive breast cancer

Background: HER2-positive breast cancer (BC) accounts for approximately 15% of all BC. HER2-targeted therapies, such as trastuzumab and lapatinib, have significantly improved the outcome for these patients. However, HER2-targeted therapy resistance is a common clinical issue. We have previously shown that protein phosphatase 2A (PP2A) plays a role in mediating acquired lapatinib resistance in HER2-positive BC and that response to lapatinib is enhancedin vitroby the lab-grade PP2A inhibitor, okadaic acid. The aim of this study was to examine the in vitro and in vivo efficacy of LB-100, a PP2A inhibitor that has completed phase I clinical testing (NCT01837667), in models of HER2-positive BC with acquired resistance to lapatinib.

Methods: HER2-positiveSKBR3 and HCC1954 BC cell lines were treated with 250 nM or 1 μM lapatinib, respectively, for 6 months to generate lapatinib-resistant SKBR3-L and HCC1954-L cell lines. In vitro sensitivity to lapatinib and LB-100 was assessed by 2D acid phosphatase assay. Combination index (CI) values were generated to identify synergistic combinations. Propidium iodide staining was used to determine cell cycle arrest and apoptosis. In order to examine the in vivo efficacy of LB-100, HCC1954-L cells were implanted into the mammary fat pad of BALB/c nude mice and treated with vehicle, lapatinib, LB-100, or lapatinib plus LB-100. To examine the prevention of the development of lapatinib resistance, SKBR3 and HCC1954 cells were treated twice weekly with lapatinib, LB-100 or the combination and stained with crystal violet when confluent.

Results: SKBR3-L and HCC1954-L cells were resistant to lapatinib at clinically relevant concentrations (IC50values = 2.37 ± 0.58 μM and 1.67 ± 0.34 μM). This represents a 46- and 5.2-fold decrease in lapatinib sensitivity. LB-100 had a greater anti-proliferative effect in the lapatinib-resistant SKBR3-L and HCC1954-L cell lines compared to their respective parental cell lines (IC50values = 2.12 ± 0.2 μM v 5.38 ± 0.6 μM, and 2.31 ± 0.19 μM v 5.32 ± 0.82 μM, respectively). LB-100 overcame lapatinib resistance in both models, as lapatinib plus LB-100 was synergistic in both cell lines (CI values = 0.56 ± 0.13 and 0.68 ±0.26). LB-100 caused cell death through the induction of apoptosis in SKBR3- L (p = 0.019) and HCC1954-L (p = 0.046) and the addition of lapatinib to LB-100 increased apoptotic induction in HCC1954-L cells (p=0.046).Lapatinib plus LB-100 was well tolerated in vivo. The HCC1954-L cell line maintained resistance to lapatinib in vivo and the combination of lapatinib and LB-100 significantly reduced HCC1954-L tumour volume compared to all other treatment arms (p = 0.0006). Interestingly, in vitro short-term resistance assays showed that the addition of LB-100 to lapatinib could also block the emergence of lapatinib resistance in both parental SKBR3 and HCC1954 cell lines.

Conclusions: This study indicates that LB-100 has in vitro and in vivo efficacy against lapatinib-resistant HER2-positive BC cell line models and justifies further investigation into its potential to circumvent or prevent lapatinib resistance in HER2-positive BC.

Citation Format: Conlon N, McDermott M, Browne B, Roche S, O'Neill F, Meiller J, Browne A, Eustace A, Collins DM, O'Donovan N, Crown J. Pre-clinical investigation of PP2A inhibitor LB-100 in overcoming and preventing lapatinib resistance in HER2-positive breast cancer [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 P5-03-02.

Abstract PD5-09: Immune parameters associated with survival in triple negative and HER2-positive breast cancer patients with 10 years of follow-up

The clinical utility of tumor-infiltrating lymphocytes (TIL) is actively being investigated in breast cancer (BC). It is unclear whether TIL spatial location and organization in tertiary lymphoid structures (TLS) have an impact on prognosis. Additionally, the significance of PD-1 and PD-L1 expression is being debated due to conflicting data from several studies. We hypothesize that the presence, extent and spatial location of multiple immune biomarkers, reflecting ongoing immune responses, will be consistently associated with a good prognosis in highly infiltrated BC [triple-negative (TNBC) and HER2+].

The relationship between these immune biomarkers and clinical outcome was examined in the TNBC and HER2+ cohorts of node-positive BC patients enrolled in the BIG 02-98 adjuvant phase III trial with available material for immunohistochemical (IHC) labeling (N=113 and N=136, respectively). HER2+ patients did not receive trastuzumab. Dual IHC staining was performed on full-face consecutive tissue sections. Scoring was independently performed by two pathologists, blinded to the clinical data, and included: global, intratumoral and stromal TIL and TLS, assessed on CD3/CD20 slides; the percentage and location of PD-1 and PD-L1 expression, assessed on PD-1/PD-L1 slides. TIL were considered as a categorical variable with different cut-offs used for each parameter and for each cohort (TNBC and HER2+). Invasive disease-free survival (I-DFS) and overall survival (OS) were analyzed (median follow-up: 10 years). Cox proportional hazard models were used for survival analyses.

The TNBC cohort revealed an association between global TIL and outcome [adjusted hazard ratio (HR) for I-DFS: 0.27 (0.15-0.51); OS: 0.26 (0.13-0.53)]. Similar results were observed for stromal and intratumoral TIL. PD-L1 expression within TLS was an independent predictor of OS, after adjustment for tumor size and age [HR: 0.30 (0.09-0.99)]. Multivariate analysis reveals this effect was principally driven by high stromal TIL (&gt;17.5% based on CD3/CD20 assessment) (χ2 OS: p=0.009). In contrast, no significant prognostic associations were found in the overall HER2+ cohort. However high T cell TIL were associated with improved I-DFS and OS in the ER-/HER2+ group [I-DFS: 0.34 (0.14-0.80); OS: 0.32 (0.12-0.86)] and stromal TIL were associated with improved I-DFS in the ER+/HER2+ group [HR: 0.29 (0.09-0.94)] (univariate analyses). No significant associations between the number of TLS nor the expression of PD-1 with outcomes were observed in either cohorts.

The presence of PD-L1+ TLS, driven by high baseline TIL, was associated with an excellent prognosis in node-positive TNBC. This observation might reflect specific immune activities taking place in these mini lymph node-like structures adjacent to the tumor bed where specific antitumor memory immune responses could be generated. No different prognostic impact was observed when analyzing TIL spatial location. Although the statistical power of the study might be limited, in line with previous findings our data reveal that, among the immune parameters evaluated, TIL are the strongest predictor of outcome in TNBC, while PD-L1+ TLS could be a new and important parameter that requires further investigation.

Citation Format: Solinas C, de Wind A, Van den Eynden G, Ameye L, Garaud S, De Silva P, Boisson A, Noel G, Langouo Fontsa M, Buisseret L, de Azambuja E, Francis PA, Di Leo A, Crown JP, Sotiriou C, Larsimont D, Paesmans M, Piccart-Gebhart M, Willard-Gallo K. Immune parameters associated with survival in triple negative and HER2-positive breast cancer patients with 10 years of follow-up [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 PD5-09.

Abstract PD3-11: HER2/ERBB2 status in “HER2 equivocal” breast cancers by FISH and ASCO-CAP guidelines: False-positives due to heterozygous deletions of alternative control loci

Background. The ASCO-CAP guidelines for HER2 testing by fluorescence in situ hybridization (FISH) have a category, referred to as “equivocal” (average HER2 copies per tumor cell &gt;4-6 with HER2/CEP17 ratio &lt;2·0), which is neither “HER2-positive” nor “HER2-negative”. Approximately 4% - 12% of invasive breast cancers are “HER2-equivocal” based on FISH. Cancers in this category may be resolved as “negative” or “positive” by FISH alternative control probes (2013/2014 guidelines) or HER2 immunohistochemistry (IHC) (2018 update). Our objectives were to evaluate the following hypotheses: 1.) Genetic loci used as alternative controls show heterozygous deletion in a substantial proportion of breast cancers; 2.) Use of these loci for assessment of HER2 by FISH leads to false-positives; 3.) HER2 FISH false-positive breast cancer patients have outcomes that do not differ from clinical outcomes for HER2-negative breast cancer patients; and 4.) HER2-equivocal breast cancers seldom show HER2 protein overexpression (IHC 3+).

Methods. We retrospectively assessed the use of chromosome 17 p-arm and q-arm alternative control genomic sites (TP53, D17S122, SMS, RARA, TOP2A), as recommended by the 2013/2014 ASCO-CAP guidelines, in patients whose data were available through the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC)(N=1980) or whose tissues were available from the BCIRG-005 clinical trial (N=3298). We used either FDA-approved HER2 IHC (HercepTest) or laboratory-developed HER2 (10H8) IHC assays to assess HER2 protein expression.

Results. Using METABRIC we found heterozygous deletions, particularly in specific p-arm sites, were common in both HER2-amplified and HER2-not-amplified breast cancers. Use of alternative control probes from these regions to assess HER2 by FISH in “HER2 equivocal” as well as HER2-not-amplified breast cancers resulted in high rates of false-positive ratios (HER2-to-alternative control ratio &gt;2·0) due to heterozygous deletions of control p-arm genomic sites used as ratio denominators. Misclassifications of HER2 status was observed not only in breast cancers with ASCO-CAP “equivocal” status but also in breast cancers with an average of &lt;4·0 HER2 copies per tumor cell. These deletions were also identified by FISH. IHC demonstrated &lt;1% of FISH “HER2-equivocal” breast cancers in BCIRG-005 had IHC3+ immunostaining, consistent with HER2-not-amplified status. Clinical outcomes of “HER2-equivocal” breast cancer patients with HER2-to-alternative control ratio &gt;2·0 did not differ significantly from clinical outcomes of those with HER2-to-alternative control ratio&lt;2·0.

Conclusion. Using chromosome 17 p-arm alternative controls, as recommended by 2013/2014 ASCO-CAP guidelines, instead of CEP17 for resolution of “HER2 equivocal” cases, is problematic due to frequent heterozygous deletions of these loci in breast cancers. The indiscriminate use of alternative control probes to calculate a HER2 FISH ratio in “HER2-equivocal” breast cancers leads to false-positive interpretations of HER2 status resulting from unrecognized heterozygous deletions in one or more of these alternative control genomic sites and incorrect HER2 ratio determinations.

Citation Format: Press MF, Seoane JA, Curtis C, Quinaux E, Guzman R, Sauter G, Eiermann W, Mackey JR, Robert N, Pienkowski T, Crown J, Martin M, Valero V, Bee V, Ma Y, Villalobos I, Slamon DJ. HER2/ERBB2 status in “HER2 equivocal” breast cancers by FISH and ASCO-CAP guidelines: False-positives due to heterozygous deletions of alternative control loci [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 PD3-11.

Abstract OT3-06-01: Phase Ib clinical trial of coPANlisib in combination with Trastuzumab emtansine (T-DM1) in pre-treated unresectable locally advanced or metastatic HER2-positive breAst cancer (BC) “PANTHERA”-CTRIAL-IE 17-13

Background:The phosphoinositide 3 kinase (PI3K) pathway is important in the oncogenic function of HER2. Aberrant activation of PI3K is implicated in resistance to trastuzumab and other HER2-targeted therapies and is frequent, with up to 22% of HER2 positive breast cancer having a PIK3CA mutation. Copanlisib is a pan-class 1 PI3K inhibitor administered i.v. with low nanomolar activity against both PI3Kα and PI3Kβ. Copanlisib has been shown to re-sensitise trastuzumab resistant cell lines to trastuzumab with synergism seen in some cell lines between copanlisib and HER2 targeted therapy.

Trial design: This is a phase Ib open label, single arm adaptive, multi-centre trial of copanlisib in combination with T-DM1. Eligible patients will receive T-DM1 at 3.6mg/kg i.v. on day 1 of a 21-day cycle plus copanlisib. Copanlisib will be administered i.v. according to the dose escalation scheme (dose level 1 is 45mg on days 1 and 8, dose level 2 is 60mg on days 1 and 8, dose level 3 is 60mg on days 1, 8, and 15). Dose level -1 will be 45 mg on day 1 in case dose de-escalation is needed. We will enrol 3 to 6 patients per dose level. All patients in each level must have completed at least the first cycle of therapy before enrolment in the next dose level. Patients not completing the first cycle for a reason other than toxicity will be replaced. Dose escalation and determination of the Maximum Tolerated Dose (MTD) will be based on the occurrence of Dose Limiting Toxicities (DLT).

Eligibility criteria:Eligible patients are those with unresectable locally advanced or metastatic HER2-positive BC who previously received trastuzumab and a taxane, separately or in combination. Participants must have adequate organ function and ECOG PS ≤ 2

Objectives:The primary objective is to determine the MTD for copanlisib in combination with T-DM1 in patients with pre-treated unresectable locally advanced or metastatic HER2-positive BC. Secondary objectives include evaluating the safety, efficacy and cardiotoxicity in patients treated with this regimen. Exploratory objectives include examining for predictive biomarkers in tumour tissue and blood or plasma and to examine molecular tumour adaptation to clinical trial therapy.

Statistical methods: Patients will be accrued in cohorts of 3 patients according to a standard 3+3 algorithm, with dose escalation and determination of MTD based on the occurrence of DLT, using the usual threshold probability of 33%. The final dose level will be expanded to include a total of 6 additional patients (expansion cohort).

Present accrual and target accrual:The trial will start accrual in October 2018. Maximum of 24 patients will be enrolled.

Citation Format: Hassan A, Gullo G, O'Reilly S, Ruiz-Borrego M, Toomey S, Grogan L, Breathnach O, Morris PG, Walshe JM, Crown J, O'Mahony D, Falcon A, Egan K, Hernando A, Teiserskiene A, Kelly CM, Coate L, Hennessy BT. Phase Ib clinical trial of coPANlisib in combination with Trastuzumab emtansine (T-DM1) in pre-treated unresectable locally advanced or metastatic HER2-positive breAst cancer (BC) “PANTHERA”-CTRIAL-IE 17-13 [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 OT3-06-01.

Abstract P3-06-13: Whole exome sequencing of HER2+ metastatic breast cancer (MBC) patients (pts) with extraordinary durable complete responses (ExdCR) to trastuzumab (T)

Background: Trastuzumab (T) has shown clinical efficacy in early-stage and MBC. However, within 1-year 40-50% develop resistance to T. The exact mechanism of the development of T resistance is not completely understood. Anecdotal observations suggest that a small fraction of patients with HER2+ MBC may be "extraordinary durable complete responders (ExdCR)". Indeed, we previously reported that 9% of MBC achieve dCR following T and chemotherapy. Understanding the genomic mechanisms underlying exceptional dCR to T may improve patient selection and treatment rationale to identify HER2+ MBC pts who are more likely to achieve dCR following T treatment.

Methods: Genomic DNA was extracted from paraffin embedded formalin fixed (FFPE) tissue. Whole exome sequencing (WES) on primary tumours from 9 MBC ExdCR &gt; 60 mo (5 matched T:N) and 6 non-responders (NR) or PR &lt; 6 mo (3 matched T:N). Tumours were analysed for single nucleotide variants (SNVs) point mutations, insertions/deletions (indels), copy number alterations (CNA), and tumour mutational burden. Detailed clinicopathologic data was collected for each patient and linked to the genomic information.

Results: WES of matched tumour:normal samples revealed differences in SNVs and indels between the ExdCR pts compared to NR. Mutations in TP53 were found in 2/5 ExdCR pts and in 0/3 NR. Initial analysis of CNA revealed that HER2 is significantly more amplified in ExdCR pts compared to NR, and this was also shown by IHC and FISH.

Conclusions: We present a genomic landscape of extraordinary durable complete responders compared to non-responders using WES. High variability exists in mutation profile of ExdCR pts with few overlapping genes. Further analysis into clinically relevant genomic and molecular alterations will be performed to potential aid in patient selection and choice of therapy, and novel drug targets.

Citation Format: Walsh N, Gullo G, Quinn C, Furney SJ, Crown J. Whole exome sequencing of HER2+ metastatic breast cancer (MBC) patients (pts) with extraordinary durable complete responses (ExdCR) to trastuzumab (T) [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 P3-06-13.

Abstract P4-07-08: Budesonide and loperamide do not impact the cytotoxicity of neratinib or HER2-directed monoclonal antibodies in HER2+ breast cancer cell lines

Background: Neratinib is an irreversible pan-HER tyrosine kinase inhibitor with demonstrated clinical activity in HER2+ and HER2-mutated breast cancers. The main toxicity of neratinib is diarrhea, which is common in the absence of prophylaxis. Preclinical models suggest that neratinib-associated diarrhea may involve inflammatory, bile acid malabsorption and secretory factors. The phase II CONTROL study is currently investigating the prophylactic efficacy of the opioid receptor antagonist loperamide in combination with budesonide (a corticosteroid used for inflammatory gastrointestinal conditions) or colestipol (bile acid sequestrant) on neratinib-associated diarrhea in early-stage HER2+ breast cancer (NCT02400476). This in vitro study examines the impact of loperamide and budesonide on the anti-proliferative activity of neratinib or trastuzumab and pertuzumab in HER2+ or HER2-low breast cancer cell lines.

Methods: HER2+ breast cancer cell lines SKBR3 (estrogen receptor [ER]–), BT474 (ER+), HCC1569 (ER–) and HER2-low, pertuzumab-sensitive MDA-MB-175-VII (ER+) breast cancer cells were investigated using a 5-day acid phosphatase-based proliferation assay to determine the concentrations required to inhibit growth by 50% (IC50). Fixed ratios of drugs were utilised in combination assays to generate Combination Index (CI) values (Calcusyn®) where available. Clinically relevant levels of neratinib, trastuzumab and pertuzumab were utilised in all experiments. Physiologically relevant levels of budesonide (˜4.2 nM) and loperamide (˜2.5 nM) were exceeded to provide IC50 values for these compounds.

Results: All cell lines tested had neratinib IC50 values in the nM range (Table). Trastuzumab and the trastuzumab/pertuzumab combination did not exceed 50% inhibition in the HER2+ cell lines. In the HER2+ breast cancer cell lines tested, loperamide had no impact on neratinib activity in BT474, enhanced neratinib activity in SKBR3, and the combination of loperamide and neratinib proved synergistic in HCC1569 (CI = 0.77 +/– 0.2). Budesonide produced strong synergism in combination with neratinib in SKBR3 (CI = 0.27 +/– 0.03), had no impact on neratinib activity in BT474 and improved response to neratinib in HCC1569. Loperamide and budesonide improved the activity of trastuzumab and pertuzumab in all three HER2+ models tested, and had no impact on pertuzumab activity in MDA-MB-175-VII. Interestingly, neratinib proved synergistic in combination with pertuzumab in MDA-MB-175-VII (CI = 0.75 +/– 0.5 nM).

Table.Anti-proliferative effects of agents testedBreast cancer cell lineNeratinib IC50, nMLoperamide IC50, nMBudesonide IC50, nMPertuzumab IC50, nMTrastuzumab (% inhibition, 2.5μg/ml)Trastuzumab/Pertuzumab (% inhibition, 2.5μg/ml)SKBR32.8 +/– 0.47.7 +/– 0.52.7 +/– 0.2NA26.3 +/– 1.3NABT4741.4 +/– 0.12.6 +/– 0.27 +/– 0.6NA40.1 +/– 4.3NAHCC156917.3 +/– 0.79.3 +/– 1.728.7 +/– 0.5No effectNo effect26.1 +/– 2.8MDA-MB-175-VII3 +/– 0.3&gt; 20&gt; 201.2 +/– 0.2NANANA = not acquired.

Conclusions: Our preclinical results suggest that budesonide and loperamide do not antagonise the anti-proliferative activity of neratinib or HER2-directed monoclonal antibodies in HER2+ breast cancer cell lines.

Citation Format: Collins DM, Gaynor N, Conlon N, Gullo G, Eustace AJ, Crown J. Budesonide and loperamide do not impact the cytotoxicity of neratinib or HER2-directed monoclonal antibodies in HER2+ breast cancer cell lines [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 P4-07-08.

Abstract P6-21-01: Xentuzumab (BI 836845), an insulin-like growth factor (IGF)-neutralizing antibody (Ab), combined with exemestane and everolimus in hormone receptor-positive (HR+) locally advanced/metastatic breast cancer (LA/mBC): Randomized phase 2 results

Background:

Xentuzumab (Xen), an IGF-1/-2-neutralizing Ab, binds IGF-1 and IGF-2, inhibits their growth-promoting signaling, and suppresses AKT activation by everolimus (Ev). This Phase 1b/2 trial evaluates Xen in combination with Ev and exemestane (Ex) in HR+/HER2− LA/mBC.

Methods:

The two-arm, open-label, randomized Phase 2 part enrolled female patients (pts) with HR+/HER2− LA/mBC not amenable to curative therapy and refractory to nonsteroidal aromatase inhibitors. Pts were randomized (1:1) to: oral Ev (10 mg/d) + Ex (25 mg/d); or Xen (1000 mg/wk iv) + Ev (10 mg/d) + Ex (25 mg/d). Randomization was stratified by visceral metastases (VM; Y vs N). Treatment continued in 28-day cycles until progression, intolerable adverse events (AEs) or other reasons for discontinuation. Primary endpoint was progression-free survival (PFS), with an interim futility analysis incorporated in the study design.

Results:

Following the results of the interim analysis, the Data Monitoring Committee (DMC) advised early termination of the trial and discontinuation of Xen treatment. Thus, Xen treatment exposure time and time-to-event data for the Xen+Ev+Ex arm are limited. Of the 139 women treated (Xen+Ev+Ex 70; Ev+Ex 69), 77% had VM. Median PFS was not significantly different between arms (Xen+Ev+Ex vs Ev+Ex, 7.3 vs 5.6 months; HR [95% CI] 0.97 [0.57–1.65]; p=0.91). In a pre-specified subgroup of pts without VM, Xen+Ev+Ex showed favorable PFS vs Ev+Ex (HR 0.21 [0.05–0.98]; Pint=0.0141). Pint values &lt;0.05 were also observed for ad hoc subgroups: measurable disease at baseline; bone-only metastases. Rates of total AEs/grade ≥3 AEs/drug-related AEs were similar between arms (Xen+Ev+Ex, 100/60/96%; Ev+Ex, 99/58/96%). The most common AEs overall were diarrhea (44 vs 33%), mucosal inflammation (39 vs 32%), rash (34 vs 33%) and stomatitis (34 vs 38%); most were grade 1/2. 6% of pts in the Xen+Ev+Ex arm discontinued Xen due to AEs. Ev/Ex discontinuations (Xen+Ev+Ex vs Ev+Ex) occurred in 13/6% vs 23/6%; 1 pt each in the Xen+Ev+Ex arm died from pneumonitis and liver injury and 1 pt each in the Ev+Ex arm died from Burkitt's lymphoma, acute kidney injury and metastases to the peritoneum.

Conclusion:

In the overall population, PFS did not improve with the addition of Xen to Ev+Ex and the trial was therefore discontinued early. Nevertheless, a favorable signal was observed in the pre-specified subgroup of pts without VM when treated with Xen+Ev+Ex, which warrants additional investigation. The safety profile was comparable between arms.

Citation Format: Crown J, Sablin M-P, Cortés J, Bergh J, Im S-A, Lu Y-S, Martínez N, Neven P, Lee KS, Morales S, Pérez-Fidalgo JA, Adamson D, Goncalves A, Prat A, Jerusalem G, Schlieker L, Espadero R-M, Bogenrieder T, Chin-Lun Huang D, Schmid P. Xentuzumab (BI 836845), an insulin-like growth factor (IGF)-neutralizing antibody (Ab), combined with exemestane and everolimus in hormone receptor-positive (HR+) locally advanced/metastatic breast cancer (LA/mBC): Randomized phase 2 results [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 P6-21-01.

Abstract P4-06-19: The effect of relieving adenosine-mediated immunosuppression on trastuzumab-mediated antibody-dependent cell-mediated cytotoxicity (T-ADCC) against HER2+ breast cancer cell lines

Introduction: Trastuzumab (T) is a monoclonal antibody therapy used in the treatment of HER2+ breast cancer. T inhibits HER2 intracellular signalling and is capable of engaging the immune system through ADCC. Adenosine is an important negative regulator of the immune response through its interaction with the A2A receptor (A2AR, ADORA2A). Relieving adenosine-mediated immunosuppression by inhibiting A2AR may improve NK cell-mediated T-ADCC against HER2+ breast cancer cells. In addition, we have previously shown that SKBR3 cells resistant to the EGFR/HER2 tyrosine kinase inhibitor (TKI) lapatinib are less sensitive to T-ADCC and showed increased A2AR protein levels. This study examines the effects of inhibiting A2AR signalling on NK cell-mediated T-ADCC against treatment naïve HER2+ breast cancer cell lines HCC1954 and SKBR3 and lapatinib and afatinib (irreversible pan-HER-family TKI)-resistant sublines of HCC1954 and SKBR3.

Methods: HER2+ breast cancer cell lines SKBR3 and HCC1954 were exposed to afatinib (150nM) or lapatinib (1μM) for 6 months to generate TKI-resistant SKBR3-A and HCC1954-L cell lines. Acid-phosphatase-based proliferation assays were used to confirm resistance to TKI treatment. Western blotting was used to examine A2AR and HER2 protein levels in cell lines. NK cells were isolated from healthy volunteer whole blood by MACSxpress isolation kits. Immune cell-mediated cytotoxicity was determined at a 1:1 (NK cell: TC) ratio over 12 hours using a flow cytometry-based method. Direct cytotoxicity and T-ADCC were determined +/- A2AR agonist CGS21680 (1 μM) and/or A2AR antagonist preladenant (100 nM) for all cell lines. Experiments were carried out three times with three separate volunteer samples with representative results presented.

Results: HCC1954-L cells were 5.3-fold resistance to lapatinib (IC50 1.65 μM +/- 0.22 μM) vs. HCC1954 (IC50 0.31 μM +/- 0.15 μM). SKBR3-A cells were 33-fold resistant to afatinib (IC50 0.28 μM +/- 0.006 nM) vs. the parental SKBR3 cell line (IC50 0.009 μM +/- 0.006 μM). SKBR3 and HCC1954 expressed detectable protein levels of A2AR. A2AR and HER2 levels were not significantly changed between parental and resistant cell lines. Levels of direct cytotoxicity and T-ADCC elicited by NK cells were higher against SKBR3-A (p=0.002) and HCC1954-L cells (p=0.0004) than parental cell lines. The A2AR agonist CGS21680 alone had inconsistent effects on direct cytotoxicity and T-ADCC in all cell lines tested. The addition of A2AR antagonist preladenant to CGS21680, but not preladenant alone, increased T-ADCC against the parental HCC1954 cells by 12.7 +/- 3.4% and parental SKBR3 cells by 9.5 +/- 3.6%. T-ADCC levels in the targeted therapy-resistant HCC1954-L and SKBR3-A cell lines were not impacted by the CGS21680/preladenant combination.

Conclusions: A HER2-targeted therapy resistance phenotype is associated with increased T-ADCC in the models tested. Inhibition of activated A2AR can increase T-ADCC elicited by NK cells against treatment naïve HER2+ breast cancer cell lines but not TKI-resistant sublines. Further work is warranted to examine the impact of targeting A2AR in HER2+ breast cancer.

Citation Format: Gaynor N, Noone J, Monedero J, Murphy EE, O'Gorman DJ, Crown J, Collins DM. The effect of relieving adenosine-mediated immunosuppression on trastuzumab-mediated antibody-dependent cell-mediated cytotoxicity (T-ADCC) against HER2+ breast cancer cell lines [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 P4-06-19.

Abstract P5-11-03: Tumor CXCL16/CXCR6 expression and soluble CXCL16 in HER2+ breast cancer (BC)

Background: CXCL16 is a pro-inflammatory chemokine associated with chemotaxis of CXCR6-expressing lymphocytes (T cells, NKT cells, NK cells) and the promotion of breast cancer cell proliferation, migration, and invasion in vitro. CXCL16 exists in a transmembrane or a cleaved, soluble form. There is limited clinically relevant data available on the CXCL16/CXCR6 signaling axis in HER2+ BC. This preliminary study examines tumor CXCL16 and CXCR6 mRNA expression and patient outcome in publicly available datasets and examines soluble CXCL16 in the plasma of 32 HER2+ BC patients enrolled in ICORG 10-05 (neo-adjuvant chemotherapy (docetaxel/carboplatin) +/- trastuzumab, lapatinib or trastuzumab/lapatinib).

Methods: CXCL16 and CXCR6 mRNA expression was interrogated in publicly available datasets using BreastMark, a web-based tool for preliminary assessment of putative biomarkers in breast cancer.A median cut-off was used for all analyses. Pre-treatment and post-treatment (2 weeks pre-surgery) blood samples were collected from patients enrolled in ICORG 10-05. Plasma CXCL16 levels were determined by Luminex xMAP assay. Pre- and post-treatment levels of CXCL16 were compared directly or based on response (pathological complete response, CR, n=14 or non-pathological complete response, nCR, n=18). Stromal lymphocyte (SL) and tumor-infiltrating lymphocyte (TIL) levels were determined from Haematoxylin and Eosin-, AE1/AE3- and CD45FFPE- stained formalin-fixed paraffin embedded tissue. Pre-treatment lymphocyte levels were correlated with pre- and post-treatment levels of CXCL16 (Pearson's product-moment correlation).

Results: In BC as a whole, analysis of publicly available datasets reveals tumor CXCL16 expression is not associated with outcome (n=1238, HR=0.9953, p=0.9516) but high tumor CXCR6 expression is (n=2652, HR=1.127, p=0.0476). Within a HER2+ cohort, inverse correlative analysis suggests high CXCR6/low CXCL16 tumor expression is significantly associated with a worse outcome (n=61, HR=2.731, p=0.01). For ICORG 10-05 patients, circulating CXCL16 plasma levels were significantly higher post-treatment (p&lt;0.0001). The magnitude of this increase was significantly greater in CR than nCR patients (p&lt;0.009). Post-treatment circulating CXCL16 levels negatively correlate with pre-treatment total (SL+TIL) lymphocyte counts (correlation coefficient -0.50 (CI -0.75- -0.13), p=0.01) in ICORG 10-05 patients. SL and total lymphocyte (SL+TIL) counts were higher in CR (n=13) vs. nCR (n=13) patients but the difference was not significant (SL, p=0.22; SL+TIL, p=0.29).

Conclusions: Our preliminary results suggest tumor levels of CXCL16/CXCR6 are associated with patient outcome and circulating levels of soluble CXCL16 are altered by treatment and correlate with tumor immune infiltrate in HER2+ BC patients. Further examination of tumor CXCL16/CXCR6 expression and circulating CXCL16 as potential biomarkers of response is warranted in a larger cohort of HER2+ BC patients.

Citation Format: Collins DM, Madden SF, Eustace AJ, Toomey S, Kay EW, Fay J, O'Donovan N, Gallagher WM, Hennessy B, Crown J. Tumor CXCL16/CXCR6 expression and soluble CXCL16 in HER2+ breast cancer (BC) [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 P5-11-03.

Abstract P5-20-05: Impact of type of (neo)adjuvant systemic therapy (AdjTx) and total exposure to trastuzumab (TET) on long-term outcome of HER2-positive (HER2+) early stage breast cancer (ESBrCa)

Background

Trastuzumab (T) administered for 12 months (mos) as part of a taxane (Tax)– or Tax+anthracycline (Anthra)–based AdjTx is the standard of care as (neo)AdjTx of HER2+ ESBrCa. Several prospective randomized trials have investigated a shorter duration of Adj T (i.e. 9 weeks or 6 mos) compared to standard 12 mos of T. However, the results have not been conclusive so far. The impact of administering non-Tax/non-Anthra-based AdjTx and single-agent T on long-term outcome of HER2+ ESBrCa is not fully known.

Methods

We conducted a retrospective analysis on a prospectively maintained departmental database of all patients (pts) with Stage I-III HER2+ ESBrCa treated with at least one dose of (neo)Adj T. Pre-planned duration of T was 12 mos for all pts. TTE was defined as the interval in weeks between the first and the last dose of T. In order to ensure that most pts had a minimum FU of 3 yrs we included all pts who received 1st T before March 31st 2014. The database was locked for outcome analyses on March 31st 2017.

Results

506 pts treated between October 2001 and March 2014 were included in the study. Main pts characteristics: median age: 55 years (range: 26-85), oestrogen (ER) and/or progesterone (PR) receptors positive: 321 (63%), axillary lymph nodes positive: 266 (52%), Adj T: 386 (76%), neoAdj T: 120 (24%), Tax- and Tax/Anthra–based AdjTx: 457 (90%), non-Tax/non-Anthra AdjTx and single-agent T (without chemotherapy): 49 (10%). Median FU is 73.3 months (range: 1.4-176.3). In the overall population, DFS and OS rates are 83% and 91%, respectively. Pts treated with non-Tax/non-Anthra AdjTx had a significantly higher risk of BrCa relapse [DFS: HR 3.54 (95%CI:1.24 to 10.06, p=0.018)], and death [OS: HR 2.73 (95%CI:0.63 to 11.77 p=0.176)] compared to those treated with Tax–based AdjTx (e.g. TCH [docetaxel/carboplatin/T]). Pts who received single-agent T also had highly significantly worse DFS [HR 4.21 (95%CI:2.18 to 8.38, p&lt;0.0001)] and OS [HR 6.75 (95%CI:3.13 to 14.6 p=&lt;0.0001)] compared to those treated with Tax-based AdjTx. When adjusted for age (&lt;55 vs &gt;55 yrs), the detrimental impact of type of AdjTx remained highly statistically significant (p&lt;0.0001). Patients with TTE&lt;24 weeks had a highly significantly worse DFS [HR 4.7 (95%CI:2.34-9.47, p&lt;0.0001)] and OS [HR 5.36 (95%CI:2.39-12.01, p&lt;0.0001)] compared to pts with TTE&gt;24weeks. In most cases, shorter duration of T was due to reduction in LVEF or patients refusal. In the multivariate model, positive lymph nodes, type of (neo)AdjTx and TET (&lt;24 weeks vs &gt;24 weeks) remained all significant and independent variables associated with worse DFS and OS.

Conclusions

Our mature results indicate that the administration of non-Tax/non-Anthra-based AdjTx and single-agent T is associated with a significant increase in the risk of disease relapse and death and should not be considered as therapeutic options for pts with HER2+ ESBrCa. The administration of T for &lt;24weeks irrespective of the type of AdjTx is also associated with significantly worse outcome.

Citation Format: Gullo G, Walsh N, Fennelly D, Walshe J, O'Mahony K, Silva N, Ballot J, Calzaferri G, Quinn C, McDonnell D, Crown J. Impact of type of (neo)adjuvant systemic therapy (AdjTx) and total exposure to trastuzumab (TET) on long-term outcome of HER2-positive (HER2+) early stage breast cancer (ESBrCa) [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 P5-20-05.

Abstract P4-03-15: Targeting Src kinase blocks development of afatinib resistance in HER2-positive breast cancer

Background: Afatinib is an irreversible pan-HER inhibitor approved for non-small cell lung cancer. We have previously shown that afatinib inhibits growth of HER2-positive breast cancer cells and enhances response to trastuzumab. However, we have also shown that long-term exposure to tyrosine kinase inhibitors leads to the development of acquired resistance. To determine if acquired afatinib resistance develops in HER2-positive breast cancer cells, we exposed a HER2-positive breast cancer cell line to afatinib for 6 months and investigated alterations in the cells following long-term exposure.

Methods: SKBR3 cells were treated with 150 nM afatinib twice-weekly for 6 months. Growth response to drug inhibitors was assessed by acid phosphatase assay. Drug sensitivity was examined in four HER2-positive cell lines (SKBR3, EFM192A, BT474 and HCC1954) and three acquired trastuzumab resistant cell lines (SKBR3-T, BT474-T and EFM192A-T). Reverse phase protein array (RPPA) was used to determine alterations in key signaling pathways. Src, p-Src, EGFR, p-EGFR, ERK1/2, p-ERK 1/2 levels were examined by Western blotting. To examine the prevention of the development of afatinib resistance, cells were treated twice weekly with afatinib, dasatinib, or the combination and stained with crystal violet when confluent.

Results: Following 6 months of afatinib treatment, the SKBR3-A cells were more resistant to afatinib compared to parental cells (IC50 SKBR3-A 284 ± 28.2 nM vs SKBR3-Par 10.9 ± 3.4 nM). Furthermore, the resistant cells were cross-resistant to lapatinib, neratinib and trastuzumab. RPPA interrogation of the SKBR3-A cells showed alterations in several pathways, including significantly increased levels of p-Src (Y416). SKBR3-A cells were more sensitive to Src inhibition with dasatinib compared to SKBR3-Par cells and the combination of afatinib and dasatinib was highly synergistic in SKBR3-A cells (CI value = 0.09 ± 0.06). The combination of afatinib and dasatinib was also synergistic in the trastuzumab resistant SKBR3-T cells (Table). Afatinib and dasatinib inhibited EGFR and Src activation and ERK 1/2 signalling in SKBR3-A cells.

Short-term resistance assays showed that the addition of dasatinib to afatinib blocks the emergence of resistant cells in three of four HER2 positive cell lines tested and two of the three acquired trastuzumab resistant cell lines tetsed.

Conclusion: HER2-positive breast cancer cells that are highly sensitive to afatinib can develop acquired resistance to afatinib within six months. Src is a potential target to prevent the development of afatinib resistance and thus combined treatment with afatinib and dasatinib may be beneficial in patients with HER2-positive breast cancer.

Percentage growth in HER2-positive cells treated with afatinib and/or dasatinib for 5 days. 20 nM Afatinib40 nM Dasatinib20 nM Afatinib + 40 nM DasatinibSKBR325.2 ± 6.1109.9 ± 6.222.6 ± 6.2SKBR3-A62.1 ± 0.787.3 ± 11.036.3 ± 0.3*SKBR3-T42.6 ± 4.9107.4 ± 9.729.3 ± 3.5*BT47418.2 ± 3.079.5 ± 5.213.3 ± 1.1BT474-T6.9 ± 2.795.3 ± 2.06.2 ± 2.3EFM192A39.1 ± 4.7105.7 ± 3.135.3 ± 2.7EFM192A-T30.4 ± 5.299.8 ± 2.528.5 ± 4.4HCC195461.8 ± 8.180.5 ± 8.219.4 ± 3.6** indicates enhanced anti-proliferative response for the combination compared to the single agents.

Citation Format: Conlon N, Canonici A, Morgan C, Cremona M, Hennessey BT, Eustace A, O'Brien N, Slamon D, Crown J, O'Donovan N. Targeting Src kinase blocks development of afatinib resistance in HER2-positive breast cancer [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 P4-03-15.

Abstract P2-05-02: Functional genomic screening identifies ubiquitin-specific protease 11 (USP11) as a novel regulator of ER-alpha transcription in breast cancer

Approximately 70% of breast cancers overexpress the estrogen receptor α (ERα) and depend on this key transcriptional regulator for growth and differentiation. The discovery of novel mechanisms controlling ERα function represent major advances in our understanding of breast cancer progression and potentially offer attractive new therapeutic opportunities. Here, we investigated the role of deubiquitinating enzymes (DUBs), which act to remove ubiquitin moieties from proteins, in regulating transcriptional activity of ERα in breast cancer.

To identify DUBs involved in the regulation of ERα transcriptional activity, we performed an RNAi loss-of-function screen using a library of shRNA vectors targeting all human DUB genes. The DUB library consisted of pools of four non-overlapping shRNAs targeting all 108 known or putative DUBs (432 shRNAs in total). We found that suppression of a number of DUBs markedly repressed or enhanced the activity of an estrogen-response-element (ERE) luciferase reporter following estradiol (E2) stimulation. Of particular interest, suppression of the BRCA2-associated DUB, USP11, was found to down-regulate ERα transcriptional activity.

Subsequent validation using two individual siRNAs targeted to USP11 revealed a notable reduction in expression of endogenous ERα target genes in the ZR-75-1 cell line, as quantified using qRT-PCR. Further validation was carried out in a HEK293T USP11 knockout cell line, where reduced activity of an ERE-luciferase reporter was detected when compared to wild-type cells. This phenotype was rescued with a USP11 overexpression vector, both in the presence and absence of E2. Furthermore, USP11 expression was found to be upregulated in the estrogen-independent cell line LCC1 when compared to their parental MCF7 cells. Knockdown of USP11 in LCC1 cells resulted in decreased mRNA expression of a panel of ERα target genes, while RNA-seq revealed a downregulation of several putative ERα target genes and a downregulation of many cell cycle-associated proteins.

To support the prognostic relevance of USP11, immunohistochemical staining of a breast cancer tissue microarray (103 ER+ patients available for final analysis) was performed. Kaplan-Meier analysis of this cohort revealed a highly significant association between high USP11 expression and poor overall (p=0.030) and breast cancer-specific survival (p=0.041). In silico analysis of publically available breast cancer gene expression datasets further supported an association between high USP11 mRNA levels and poor prognosis. We observed a significant correlation between high expression of USP11 mRNA in ER-positive patients and poor distant metastasis-free survival (HR 2, CI 1.37-2.91, p=0.00023). This correlation was also significant in ER-positive patients who had received tamoxifen only (HR 2.9, CI 1.63-5.15, p=0.00015).

These results suggest a role for USP11 in driving cellular growth and identify USP11 as novel therapeutic target in breast cancer.

Citation Format: Dwane L, Das S, Moran B, O'Connor AE, Mulrane L, Dirac AM, Jirstrom K, Crown JP, Bernards R, Gallagher WM, Ní Chonghaile T, O'Connor DP. Functional genomic screening identifies ubiquitin-specific protease 11 (USP11) as a novel regulator of ER-alpha transcription in breast cancer [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 P2-05-02.

Abstract P6-08-17: Pregnancy associated breast cancer: Evaluating maternal outcomes. A multicentre study

Background

Pregnancy associated breast cancer (PABC) is defined as breast cancer (BC) diagnosed during the gestational period (GP) or in the first year postpartum (PP). Despite its infrequent occurrence, the incidence of PABC appears to be rising due to the increasing propensity for women to delay childbirth. We have established the first combined prospective and retrospective registry study of PABC in Ireland to examine specific clinicopathological characteristics, treatments and maternal outcomes. We present the retrospective findings to date.

Methods

We performed a retrospective multicentre observational study of patients (pts) with PABC treated in the eight Irish cancer centres from August 2001 to March 2017. Data extracted included information on pt demographics, tumour biology, staging, treatment administered and maternal outcomes. Standard biostatistical methods were used for analysis.

Results

111 PABC patients were identified. Sixty pts (54%) were diagnosed during the GP and 51 (46%) within 1 year PP. Median age at diagnosis was 36 years (yrs). Table 1 illustrates baseline characteristics. Two thirds of pts were node positive and a similar proportion had grade 3 pathology. Seventy pts (63%) were estrogen receptor (ER) positive, 36 (32%) HER2 positive, 25 (22%) triple negative. Twenty-two pts (20%) were metastatic at presentation. Seven pts (6%) had a known BRCA 1/2 mutation. The median OS (overall survival) and DFS (disease free survival) for the entire cohort was 107.4 and 94.2 months respectively (resp). There was no survival difference between those diagnosed during the GP versus PP. 5 yr DFS and OS was 68.6% and 69.2% resp. This compares unfavourably to results reported by the National Cancer Registry of Ireland in a similar age-matched BC population between 2000-2012 where the 5 yr OS was 86.5%. Variables in our study associated with poorer outcomes included younger age, tumour size, node positivity and lack of estrogen expression.

Baseline characteristics PABC patients (n=11) %(n)Diagnosed in GP (n=60) %(n)Diagnosed 1yr PP (n=51) %(n)p valueDemographic    Age at diagnosis3636(25-49)36(21-44)0.31Stage    I-II54(60)55(33)53(27)0.85III23(26)23(14)23(12)1IV20(22)18(11)22(11)0.81Unknown3(3)3(2)2(1)1Pathology    Grade 366(74)70(42)63(32)0.43Node positive66(73)68(41)63(32)0.55ER+/HER2-41(45)38(23)43(22)0.69ER+/HER2+23(25)28(17)16(8)0.17ER-/HER2+14(16)17(10)12(6)0.59Triple negative22(25)17(10)29(15)0.11Surgery    Breast conservation23(26)25(15)21(11)0.82Mastectomy56(63)57(34)59(30)0.84Adjuavnt/Neoadjuvant treatment    Chemotherapy73(81)77(46)69(35)0.39Anthracycline68(55)78(36)54(19)0.03Taxane89(72)93(43)83(29)0.16Anti HER2 agent21(23)18(11)24(12)0.63Endocrine therapy64(52)63(29)66(23)0.84Radiotherapy79(64)74(34)86(30)0.85Relapse in Stage I-III    Local relapse15(13)12(6)18(7)0.55Distant relapse24(21)22(11)25(10)0.80

Conclusions

PABC patients may have a poorer outcome. Our study reported higher rates of triple negative and HER2 positive breast cancer which are associated with more aggressive biology. Prospective evaluation of clinicopathological features, pharmacokinetics of treatments selected and maternal and fetal outcomes is imperative in this distinct pt group.

Citation Format: Prior L, Teo M, Greally M, Ward C, O'Leary C, Aslam R, Darwish W, Ahmed N, Watson G, Kelly D, Kiely L, Hassan A, Gleeson J, Featherstone H, Lim M, Murray H, Gallagher D, Westrup J, Hennessy B, Leonard G, Grogan L, Breathnach O, Horgan A, Coate L, O'Mahony D, Coate L, O'Reilly S, Gupta R, Keane M, Duffy K, O'Connor M, Kennedy J, McCaffrey J, Higgins M, Kelly C, Carney D, Gullo G, Crown J, Walshe J. Pregnancy associated breast cancer: Evaluating maternal outcomes. A multicentre study [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 P6-08-17.

Abstract OT3-06-05: A phase Ib/II trial of coPANlisib in combination with tratuzumab in pretreated recurrent or metastatic HER2-positive breast cancer “PantHER”

Background

The phosphoinositide 3 kinase (PI3K) pathway is important in the oncogenic function of HER2. Aberrent activation of PI3K is implicated in resistance to trastuzumab and other HER2-targeted therapies and is frequent, with up to 22% of HER2 positive breast cancer having a PIK3CA mutation. Copanlisib is a pan-class 1 PI3K inhibitor that shows particular activity against PI3Kα, the isoform encoded by the PIK3CA gene. Copanlisib has been shown to re-sensitise trastuzumab resistant cell lines to trastuzumab with synergism seen in some cell lines between copanlisib and HER2 targeted therapy.

Trial design

The study is a phase Ib/II open label, single arm adaptive, multi-centre trial of copanlisib in combination with trastuzumab. Eligible patients are treated with a dose escalation schedule of copanlisib IV on Days 1, 8 and 15 of a 28 day cycle with trastuzumab 2 mg/kg weekly (loading dose of 4 mg/kg in cycle 1). The phase II dose will be based on the maximum tolerated dose (MTD) established in Phase Ib. Patients are treated until radiologic or symptomatic progression, unacceptable toxicity, consent withdrawal or physician's decision.

Eligibility criteria

Eligible patients must have recurrent incurable or metastatic HER2-positive breast cancer that has progressed on at least one prior line of trastuzumab or T-DM1-based treatment regimen in this setting. Patients with treated and controlled brain metastases are eligible. Participants must have adequate organ function and ECOG PS ≤ 2. Patients recruited for the Phase II part of the study must have a PIK3CA mutation. Patients with uncontrolled arterial hypertension, uncontrolled diabetes or recent clinically serious infections are excluded.

Specific aims

The primary end point for the phase Ib part of this study is to determine the MTD for the combination. For the phase II study is anti-tumour efficacy, measured by Clinical Benefit Rate (CBR).

Secondary end points are evaluation of safety and tolerability, progression-free survival, time to treatment failure, duration of response and overall survival. Incorporated translational endpoints include examination of molecular tumor adaptation in tissue and blood. Given the role of PI3K in cellular glucose metabolism, an additional exploratory objective is to determine if quantitive reduction in metabolic signal on Positron Emission Tomography-Computed Tomography (PET-CT) is predictive of benefit from therapy.

Statistical methods

To establish the MTD, we use a modified 3+3 design where 3 additional patients will be accrued even if the first 3 patients accrued experience no dose limiting toxicities (DLT) in sequential cohorts for a planned 12 patients. To determine the CBR, a one sample exact binomial test with a one sided significance level of 5%, 19 evaluable patients will provide &gt;80% power to detect a difference between the null hypothesis proportion of 30% for CBR versus the alternative hypothesis proportion of 65%.

Present accrual and target accrual

There are 9 patients recruited so far to the phase Ib part of this study. Target accrual is 12 and for phase II is 19 patients.

Contact information for people with a specific interest in the trial

Prof Bryan Hennessy, Beaumont Hospital, Dublin Ireland

Funded by Bayer

Citation Format: Keegan NM, Walshe J, Gullo G, Kennedy J, Bulger K, Kelly CM, Crown J, Toomey S, Egan K, Kerr J, Given M, Hernando A, Teiserskiene A, Grogan L, Breathnach O, Morris PG, Keane M, Hennessy BT. A phase Ib/II trial of coPANlisib in combination with tratuzumab in pretreated recurrent or metastatic HER2-positive breast cancer “PantHER” [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 OT3-06-05.

Abstract P4-21-27: Plasma chemokine profile of HER2+ breast cancer (BC) patients treated with docetaxel (D) and carboplatin (C) in combination with trastuzumab (T) and/or lapatinib (L) in the neo-adjuvant setting

Background: Chemokines (chemotactic cytokines) are key regulators of the immune response, attracting immune cells to sites of inflammation, activating adhesion molecules, promoting extravasation and influencing T-cell subset polarization. Recent clinical data has shown a strong correlation between tumor infiltrating lymphocytes (TILs) and response to T therapy in HER2+ BC while the combination of chemotherapy, T and L has proven superior to chemotherapy and T alone in the neo-adjuvant setting (NeoALTTO). This preliminary study examines the levels of 40 circulating chemokines in 32 HER2+ BC patient plasma samples from ICORG 10-05 (neo-adjuvant DCT, DCL or DCTL) to investigate differences in chemokine profiles between treatment arms and patient's response to treatment.

Methods: Pre-treatment blood samples were collected before commencement of chemotherapy; post-treatment samples were collected two weeks prior to surgery. All patients received G-CSF concurrent with treatment. A panel of 40 chemokines and chemokine-associated cytokines were assessed by Luminex xMAP multiplex assay. Matched patient samples were run in single replicates and analysed together (n=32) or by comparing DCT (n=12) and DCTL (n=14) treatment arms (using a paired Mann-Whitney test and adjusting for multiple testing using Bonferroni correction). DCL (n=6) was omitted from the arm comparison due to low numbers. In addition, principle components analysis (PCA) was used to explore any trends within the data based on patient response (pathological complete response (pCR, n=15), partial response (PR, n=12), and non-response (NR, n=4)). 12 non-age matched healthy volunteer controls were also included in the PCA.

Results: PCA shows a clear separation between pre- and post-treatment samples. 30 of the 40 chemokines examined were significantly differentially expressed (adjusted p-value of &lt;0.05) post-treatment across all treatment arms. When comparing DCT and DCTL, nine chemokines were significantly altered post-therapy in both arms with two chemokines, CCL24 (p=0.039) and IL-16 (p=0.039), increased in DCT only and ten chemokines, CCL11 (p=0.009), CX3CL1 (p=0.004), CXCL1 (p=0.009), CCL1 (p=0.024), IL-2 (p=0.043), IL-6 (p=0.034), IL-8 (p=0.004), CXCL11 (p=0.004), CXCL16 (p=0.004) and TNF-alpha (p=0.004) altered in DCTL only. PCA identified no trend between pre- and post-treatment chemokine levels and response.

Conclusions: DCT and DCTL produce statistically different alterations in the plasma chemokine profiles of HER2+ BC patients. Pre- or post-treatment levels of the chemokines examined are not collectively predictive of patient response to treatment. Further work is required to elucidate the relevance of DCT- and DCTL-specific chemokine alterations to response.

Citation Format: Collins DM, Madden SF, Gaynor N, Gallagher WM, O'Donovan N, Crown J. Plasma chemokine profile of HER2+ breast cancer (BC) patients treated with docetaxel (D) and carboplatin (C) in combination with trastuzumab (T) and/or lapatinib (L) in the neo-adjuvant setting [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 P4-21-27.

Abstract P5-14-12: Long-term outcome of HER2-normal early stage breast cancer (ESBC) patients (Pts) treated with docetaxel-cyclophosphamide (TC) chemotherapy (CTx): Mature results of a single-institution experience

BACKGROUND

Anthracycline(A)-containing regimens (AReg) became an established standard (neo)adj CTx for ESBC following fairly consistent demonstration of a modest superiority over older anti-metabolite/alkylating CTx. However, substantial translational data and a recently presented pooled analysis [Blum, 2016] suggest that this superiority could be largely driven by greater benefits in specific ESBC subgroups, i.e. HER2-altered BrCa (due to co-amplification of topoisomerase 2 and HER2), and triple-negative BrCa (TNBC). A are cardiotoxic (including late onset of cardiomyopathic congestive heart failure) and potentially leukaemogenic. In late 2006, following the results of the first USONC randomized clinical trial that showed superior outcomes of the non-AReg TC (docetaxel/cyclo­phosphamide) over AC, we established a routine, uniform policy of TC for all Pts receiving (neo)adj CTx for HER2-normal ESBC. We report the mature follow up of this single-institution unselected experience.

METHODS

We performed a retrospective outcome analysis of all Pts who received at least 1 cycle of (neo)adj TC (docetaxel 75 mg/m2 + cyclophosphamide 600 mg/m2 IV every 3 weeks) at our Department for HER2-normal ESBC and with at least 5 years of follow up (FU). Pts were identified by systematic analysis of the dataset of the Oncology Pharmacy Unit. Information on tumour characteristics [e.g. axillary lymph nodes (N) metastases, hormonal receptors (HR) and HER2 status] and Pts FU were retrieved and collected into an ad hoc designed database. Pts with node-positive (N+) ESBC received TC×6 cycles, and Pts with high-risk node-negative (N−) [e.g. primary tumour (T) &gt;2 cm, or HRneg, or T &gt;3 cm] ESBC received TC×4 cycles. Pts received adjuvant hormone therapy and radiotherapy as per standard of care. From 2008 on, many lower risk HR+/N− Pts were not given CTx due to OncotypeDx availability.

RESULTS

Between September 2006 and December 2015, 810 female HER2-normal ESBC Pts were treated with (neo)adj TC. In the final outcome analysis we included 464 Pts treated before June 2011 thus having a minimum FU of 5 years. Pts characteristics are: median age 53 yrs (range 30-77), N− 246 (53%), N+ 218 (47%), hormone receptors positive (HR+) 391 (84%), TNBC 73 (16%). The database was locked as of June 1st 2016. Median FU from first cycle of TC is 7.5 yrs (range 5.3-10). 63 BrCa-specific relapse events (defined as time to local, regional or distant recurrence, invasive contralateral breast cancer, excluding non-breast second primaries) have been observed, accounting for an overall Relapse-Free Survival (RFS) rate of 86.4%. 42 deaths have occurred, 36 (86%) due to BrCa, accounting for an Overall Survival (OS) rate of 91%. RFS and OS rates for the different Pts subgroups are reported in Table 1

Table 1 - Outcome parameters RFS (%)OS (%)All Pts8691HR+/N-9396HR+/N+8190TN/N-9191TN/N+5858

CONCLUSIONS

These mature data with long FU suggest that the outcome for a large cohort of unselected Pts with HER2-normal HR+ ESBC (regardless of nodal status) and for TN/N− ESBrCa treated with nonAReg TC is excellent. However, N+TN ESBrCa in this setting remains a significant clinical challenge.

Citation Format: Losurdo A, Gullo G, Buckley C, Lowry C, Ballot J, Silva N, Hammond L, Crown J. Long-term outcome of HER2-normal early stage breast cancer (ESBC) patients (Pts) treated with docetaxel-cyclophosphamide (TC) chemotherapy (CTx): Mature results of a single-institution experience [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 P5-14-12.

Abstract P1-05-18: Genomic copy number alterations (CNA) associated with pCR in HER2-positive (HER2+) early-stage breast cancer (BrCa) patients receiving neoadjuvant trastuzumab (T)

Introduction: Genetic alterations such as amplifications and deletions frequently contribute to tumorigenesis. These alterations can change gene expression which alters the normal cell growth and survival regulatory mechanisms. Characterisation of DNA copy number alterations (CNA) is important to understand cancer progression and response to therapy. The aim of this study is to determine patterns of CNAs in HER2+ early-stage BrCa patients achieving pathological complete response (pCR) to neoadjuvant T therapy.

Methods: Retrospective analysis of our database of 95 HER2+ BrCa (stages I-III) who received T neoadjuvantly revealed 46 % (44/95) achieved pCR compared with 53 % (51/95) who did not respond (NR). DNA from pre-treatment tumour biopsy specimens from neoadjuvant T therapy patients was extracted, and array-based comparative genomic hybridization (aCGH, n = 8; 6 pCR:2 NR) was used to identify CNAs, which correlated with pCR. Pathway analysis was then used to identify functionally relevant genes in aberrant regions.

Results: aCGH analysis of DNA from pCR and NR identified distinct patterns of CNAs. HER2 amplicon was confirmed by IHC and aCGH in all samples. Although there was no significant difference in the average CNAs between groups (20±17 vs 17±2), there was greater variation in the range of CNAs in pCR (8-56 CNA) compared to NR (15-19 CNA). More gains and amplifications were observed in pCR patients with more deletions in the NR group. The most common chromosomal amplification region included chr8q12.1-q24 with 87.5% of all cases displaying gains. Of the 6 patients who achieved pCR, 50% displayed a deletion in chr9 spanning p24.3-p21.3, consistent with a deletion of tumour suppressor CDKN2A. No aberrations in chr9 were observed in NR cohort. The deleted genomic region contained 65 common protein-coding genes, with the interferon biological pathway as the most significant (p=1.03E-36).

Conclusions: Distinct genomic CNAs were observed between patients achieving pCR compared to NR. However, of the 8 pts characterised here, none have relapsed. Follow-up data revealed a relapse rate of 6.8 % (3/44) vs 11.8 % (6/51) in the pCR and NR groups, respectively. To further elucidate the immunological response, we will present CNA data patterns on relapse and response and compare the impact of CNAs, immune-related proteins and pCR as surrogate predictors for outcome.

Citation Format: Walsh N, Gullo G, Maguire A, O'Donovan N, Quinn C, Crown J. Genomic copy number alterations (CNA) associated with pCR in HER2-positive (HER2+) early-stage breast cancer (BrCa) patients receiving neoadjuvant trastuzumab (T) [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 P1-05-18.

Mutant p53: a novel target for the treatment of patients with triple-negative breast cancer?

The identification and validation of a targeted therapy for patients with triple-negative breast cancer (TNBC) is currently one of the most urgent needs in breast cancer therapeutics. One of the key reasons for the failure to develop a new therapy for this subgroup of breast cancer patients has been the difficulty in identifying a highly prevalent, targetable molecular alteration in these tumors. Recently however, the p53 gene was found to be mutated in approximately 80% of basal/TNBC, raising the possibility that targeting the mutant p53 protein product might be a new approach for the treatment of this form of breast cancer. In this study, we investigated the anti-cancer activity of PRIMA-1 and PRIMA-1^MET (APR-246), two compounds which were previously reported to reactivate mutant p53 and convert it to a form with wild-type (WT) properties. Using a panel of 18 breast cancer cell lines and 2 immortalized breast cell lines, inhibition of proliferation by PRIMA-1 and PRIMA-1^MET was found to be cell-line dependent, but independent of cell line molecular subtype. Although response was independent of molecular subtype, p53 mutated cell lines were significantly more sensitive to PRIMA-1^MET than p53 WT cells (p = 0.029). Furthermore, response (measured as IC₅₀ value) correlated significantly with p53 protein level as measured by ELISA (p = 0.0089, r=-0.57, n = 19). In addition to inhibiting cell proliferation, PRIMA-1^MET induced apoptosis and inhibited migration in a p53 mutant-dependent manner. Based on our data, we conclude that targeting mutant p53 with PRIMA-1^MET is a potential new approach for treating p53-mutated breast cancer, including the subgroup with triple-negative (TN) disease.

Impact of palbociclib plus letrozole on pain severity and pain interference with daily activities in patients with estrogen receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer as first-line treatment

Background Palbociclib is a recently approved drug for use in combination with letrozole as initial endocrine-based therapy for the treatment of postmenopausal women with advanced estrogen receptor-positive/human epidermal growth factor receptor 2-negative (ER+/HER2-) breast cancer. This report assesses the impact of palbociclib in combination with letrozole versus letrozole alone on patient-reported outcomes of pain. Methods Palbociclib was evaluated in an open-label, randomized, phase II study (PALOMA-1/TRIO-18) among postmenopausal women with advanced ER+/HER2- breast cancer who had not received prior systemic treatment for their advanced disease. Patients received continuous oral letrozole 2.5 mg daily alone or the same letrozole dose and schedule plus oral palbociclib 125 mg, given once daily for 3 weeks followed by 1 week off over repeated 28-day cycles. The primary study endpoint was investigator-assessed progression-free survival in the intent-to-treat population, and these results have recently been published (Finn et al., Lancet Oncol 2015;16:25-35). One of the key secondary endpoints was the evaluation of pain, as measured using the Brief Pain Inventory (BPI) patient-reported outcome tool. The BPI was administered at baseline and on day 1 of every cycle thereafter until disease progression and/or treatment discontinuation. Clinical trial registration This study is registered with ClinicalTrials.gov (NCT00721409). Results There were no statistically significant differences in Pain Severity or Pain Interference scores of the BPI between the two treatment groups for the overall population or among those with any bone disease at baseline. A limitation of the study is that results were not adjusted for the concomitant use of opioids or other medications used to control pain. Conclusions The addition of palbociclib to letrozole was associated with increased efficacy without negatively impacting pain severity or pain interference with daily activities.

Long-term outcomes after adjuvant treatment of sequential versus combination docetaxel with doxorubicin and cyclophosphamide in node-positive breast cancer: BCIRG-005 randomized trial

BACKGROUND

The optimal regimen for adjuvant breast cancer chemotherapy is undefined. We compared sequential to concurrent combination of doxorubicin and cyclophosphamide with docetaxel chemotherapy in women with node-positive non-metastatic breast cancer. We report the final, 10-year analysis of disease-free survival (DFS), overall survival (OS), and long-term safety.

PATIENTS AND METHODS

A total of 3298 women with HER2 nonamplified breast cancer were randomized to doxorubicin and cyclophosphamide every 3 weeks for four cycles followed by docetaxel (AC → T) every 3 weeks for four cycles or docetaxel, doxorubicin, and cyclophosphamide (TAC) every 3 weeks for six cycles. The patients received standard radiotherapy and endocrine therapy and were followed up for 10 years with annual clinical evaluation and mammography.

RESULTS

The 10-year DFS rates were 66.5% in the AC → T arm and 66.3% in the TAC arm (P = 0.749). OS was 79.9% in the AC → T arm and 78.9% in the TAC arm (P = 0.506). TAC was associated with higher rates of febrile neutropenia, although G-CSF primary prophylaxis greatly reduced this risk. AC → T was associated with a higher rate of myalgia, hand-foot syndrome, fluid retention, and sensory neuropathy.

CONCLUSION

This 10-year analysis of the BCIRG-005 trial confirmed that the efficacy of TAC was not superior to AC → T in women with node-positive early breast cancer. The toxicity profiles differ between arms and were consistent with previous reports. The TAC regimen with G-CSF support provides shorter adjuvant treatment duration with less toxicity.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT00312208.

Abstract P1-13-07: Superiority of tandem high-dose chemotherapy (HDC) versus conventionally dosed chemotherapy (CDC) in patients with metastatic breast cancer (MBC): Long term follow-up of IBDIS: A prospective random assignment trial (PRT)

Background

The partial chemo-sensitivity of MBC, together with pre-clinical models, provided a rationale for studies of extreme dose-escalation with autologous haematopoietic progenitor support (ASCT). Early studies of HDC as salvage following failure of CDC produced high rates of temporary response. Subsequent single arm studies in pts who were preselected for responsiveness to CDC yielded 10-20% durable remissions suggesting that HDC might cure some MBC pts. The likelihood of selection bias mandated randomised trials of this CDC induction-HDC consolidation approach. We hypothesised that an alternative strategy-accelerated multi-cycle HDC- might provide an optimal HDC strategy (Crown J, Norton L, Ann Oncol 1996).

Methods

In IBDIS, pts received a brief phase of CDC induction (doxorubicin/docetaxel-"AT"), followed by tandem cycles of HDC, or, further CDC (AT followed by CMF), as initial CRx for MBC. Hormone receptor-positive patients received endocrine therapy post-chemotherapy, and pts with localized metastases received consolidative radiotherapy.

Results: Accrual failed in the aftermath of the disclosure of research fraud involving a South African HDC study, and the reporting of negative PRCTs at ASCO 1999. Only 110 of a planned 264 patients were enrolled, but it was decided to maintain follow-up, which is now 15 years. HDC and CDC groups were well-balanced for prior adjuvant (25 v 25), prior anthracycline (8 v 10), positive receptor status (32 v 31). There were 8 treatment-related deaths (6-HDC, 2 CDC). Complete and overall response rates (CR/OR) were significantly superior for HDC v CDC (CR-29% v 6%, OR-71% v 44%). Event-free-survival at median 5 yrs were HDC 6 (11%) versus CDC 0 (p=.027). At fifteen years three HDC pts remain alive and free from relapse. All CDC are deceased. The hazard ratio for PFS is currently 0.59 (0.39-0.88) favouring HDC p=.009. The HR for overall survival is 0.72 (0.48-1.08)p=.11

Discussion:

Despite accrual failure, IBDIS was and remains a positive study for its primary endpoint of PFS. The 100% relapse and death rate for CDC on our study is typical of the published literature. Data from IBDIS are included in the Cochrane meta-analysis of HDC which showed an advantage for PFS. The contention that HDC produced superior activity to CDC appears to have been correct, however the magnitude of the benefit is smaller than was hoped by investigators in the field.

While our data support the hypothesis that there is a dose response relationship in the chemotherapy of MBC, the small benefit and high toxicity of HDC, preclude it being recommended as a standard treatment for any pts with MBC.

Citation Format: Crown J. Superiority of tandem high-dose chemotherapy (HDC) versus conventionally dosed chemotherapy (CDC) in patients with metastatic breast cancer (MBC): Long term follow-up of IBDIS: A prospective random assignment trial (PRT). [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 P1-13-07.

Abstract P4-14-15: Pre-treatment stromal tumour-infiltrating lymphocytes (S-TILs) are correlated with complete response (CR) to chemotherapy (Chemo) plus trastuzumab (T) in HER2-positive (H+) metastatic breast cancer (MBC)

Background. We have previously reported that ChemoT produces durable (&gt;5 years) CR in a minority of pts with H+MBC, prompting a search for predictive markers. Extensive lymphocytic infiltration of cancers is correlated with high levels of immune gene signatures. International consensus guidelines on TILs define "lymphocyte-predominant BC" at a threshold of S-TILs of 50-60% versus tumour cells. High levels of S-TILs has been correlated with improved outcome in HER2+ early stage BC pts treated with ChemoT. We investigated the degree of S-TIL infiltration in metastatic biopsies from pts with HER2+MBC prior to ChemoT, and attempted to determine whether S-TILs predicted CR in HER2+MBC.

Methods. We searched a database of all pts with HER2+ MBC treated at our institution with anti-HER2 therapy over 15yrs to identify pts who achieved CR according to RECIST 1.0 criteria, which lasted for at least 6 months. We matched them with an equal number of pts from the database who were treated during the same period, but who had progressive (POD) or stable disease (SD) as best response to T. Pts must have at least one pre-treatment tumour sample available for S-TILs assessment, and adequate clinical and follow-up information. S-TILs (mononuclear cells including lymphocytes and plasma cells) contained within the boundaries of invasive tumour were identified on a representative haematoxylin and eosin stained slide and scored as a percentage of the stromal area alone, according to the International TILs Working Group 2014 methodology [Salgado R, 2015]. S-TILs were assessed specifically for this study by a senior pathologist who scored the samples and who was blinded to pts response and clinical details.

Results. Out of 246 MBC pts registered in the HER2+ database we identified 31 CR pts with at least one available pre-treatment metastatic sample. A cohort of 31 matching POD-SD pts was randomly obtained from the same database. In 8 cases (7 CR / 1 POD-SD) S-TILs could not be assessed due to inadequate material, or for other technical reasons. The final study sample is 54 pts (24 CR / 30 POD-SD). Pts characteristics are as follows: median age (range): CR 55 (29-78) / POD-SD 56 (26-89), hormone receptor (HR) pos: CR 12 (50%) / POD-SD 18 (60%), De Novo MBC at diagnosis: CR 13 (54%) / POD-SD 8 (27%) [p&lt;0.05]. All pts received chemotherapy with T (+ lapatinib in 3 pts as part of a clinical trial), and continued on T until POD. Pre-treatment S-TILs &gt;50% were statistically significantly more frequent in CR (50% of pts) than POD/SD (20%) [chi-square p=0.02]. No statistically significant difference in the HR status was observed between the two groups (CR vs POD-SD) or between the high and low S-TILs pts.

Conclusions. S-TILs &gt;50% in the pre-treatment tumour biopsy of HER2+MBC were significantly correlated with subsequent CR to ChemoT, supporting the hypothesis that the immunological effects of T may play a role in determining response. Speculatively, S-TILs might identify pts with a higher likelihood of benefit from T. Further study of the potential role of S-TILs as predictors of T benefit are required.

Citation Format: Gullo G, Quinn C, Zacchia A, Fennelly D, Defrein A, Ballot J, Zanoni D, Walshe J, Maltese M, McDermott E, Crown J. Pre-treatment stromal tumour-infiltrating lymphocytes (S-TILs) are correlated with complete response (CR) to chemotherapy (Chemo) plus trastuzumab (T) in HER2-positive (H+) metastatic breast cancer (MBC). [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 P4-14-15.

Abstract P4-13-02: Treatment patterns of post-disease progression in the PALOMA-1/TRIO-18 trial

Background

Palbociclib (P) is an oral CDK4/6 inhibitor. In PALOMA-1/TRIO-18, a randomized phase 2 trial, addition of P to letrozole (L) significantly prolonged progression-free survival (PFS) (20 mo with P+L vs 10 mo with L alone; HR = 0.488, P=0.0004; Finn et al, Lancet Oncol, 2015) in postmenopausal women with estrogen-receptor-positive (ER+), HER2-negative advanced breast cancer (ABC) in the first-line setting. At the time of final PFS analysis, overall survival (OS) was immature.

Objectives

It is clinically important to understand whether patients (pts) benefit from standard of care endocrine therapy (ET) after they progressed on P+L as first-line treatment for ABC. We report patterns of post-progression treatment in the next line of therapy immediately following participation in the PALOMA-1 trial.

Methods

Postmenopausal women with ER+ and HER2- ABC who had not received any treatment for their advanced disease were randomized to receive P+L (N = 84) or L alone (N = 81) in the first-line setting. The primary endpoint was investigator-assessed PFS. Tumor assessment was performed every 8 weeks. Post-progression treatment data was captured and analyzed.

Results

As of the data cut-off (Nov 29, 2013), 40 progression events had occurred in the P+L arm and 59 in the L alone arm. 50% of pts in the P+L arm vs. 64% in the L alone arm received ET after progression on study treatment. 60% of pts in the P+L arm vs. 66% in the L alone arm received chemotherapy (CT) after progression on study treatment. The time to 1st subsequent ET/ CT after progression on study treatment, duration of 1st subsequent ET/CT, and choice of 1st subsequent ET/ CT are shown in Table 1.

Table 1 P + LL N=84N=81Patients (pts) with Disease Progression, NN (%)a40 (47.6)59 (72.8)Pts who received subsequent Endocrine Therapy (ET) after progression on study treatment, n(%)b20 (50.0)*38 (64.4)*Time from randomization to 1st subsequent ET (days), median (range)465.5 (239-1100)368.5 (65-1102)Duration of 1st subsequent ET (days), median (range)**153 (24-592)151 (16-1135)Choice of 1st subsequent ET, n(%)bFulvestrant9 (22.5)15 (25.4)Exemestane6 (15.0)9 (15.3)Medroxyprogesterone4 (10.0)1 (1.7)Letrozole1 (2.5)5 (8.5)Tamoxifen08 (13.6)Pts who received subsequent Chemotherapy (CT) after progression on study treatment, n(%)b24 (60.0)*39 (66.1)*Time from randomization to 1st subsequent CT (days), median (range)388.5 (69-918)281 (46-1013)Duration of 1st subsequent CT (days), median (range)**92 (1-457)120 (1-1143)Choice of 1st subsequent CT, n(%)bCapecitabine1 (2.5)10 (17.0)Mitoxantrone13 (32.5)1 (1.7)Paclitaxel013 (22.0)Other10 (25)15 (25.4)apercentages are based on N as denominator; bpercentages based on NN as denominator; *some patients had both ET and CT after progression; **calculated as treatment stop date minus treatment start date +1; if treatment was ongoing at time of data cut-off, stop date was imputed as Nov 29, 2013.

Conclusions

P+L delayed the time to ET/CT as compared to L alone. Pts benefited from standard of care ET/CT after they progressed on P+L as first-line treatment for ABC as demonstrated by the length of time on subsequent therapies; no difference was observed from the L alone arm.

Clinical Trial Information: NCT00721409

Funding Source: Pfizer.

Citation Format: Finn RS, Crown JP, Ettl J, Pinter T, Thummala A, Shparyk Y, Patel R, Randolph S, Kim S, Huang X, Nadanaciva S, Huang Bartlett C, Slamon DJ. Treatment patterns of post-disease progression in the PALOMA-1/TRIO-18 trial. [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 P4-13-02.