Soluble urokinase plasminogen activator receptor and cardiotoxicity in doxorubicin-treated breast cancer patients: a prospective exploratory study

BACKGROUND

Soluble urokinase plasminogen activator receptor is an inflammatory biomarker that may prognosticate cardiovascular outcomes. We sought to determine the associations between soluble urokinase plasminogen activator receptor and established markers of cardiotoxicity in breast cancer patients receiving doxorubicin.

METHODS

We conducted a prospective cohort study of women with newly diagnosed breast cancer receiving standard-dose doxorubicin (240 mg/m2) at Rush University Medical Center and Rush Oak Park Hospital (Chicago, IL) between January 2017 and May 2019. Left ventricular ejection fraction, global longitudinal strain, and cardiac biomarkers (N-terminal prohormone B-type natriuretic peptide, troponin-I, and high-sensitivity C-reactive protein) were measured at baseline and at intervals up to 12-month follow-up after end of treatment. The associations between soluble urokinase plasminogen activator receptor and these endpoints were evaluated using multivariable mixed effects linear regression.

RESULTS

Our study included 37 women (mean age 47.0 ± 9.3 years, 60% white) with a median baseline soluble urokinase plasminogen activator receptor level of 2.83 ng/dL. No participant developed cardiomyopathy based on serial echocardiography by one-year follow-up. The median percent change in left ventricular strain was -4.3% at 6-month follow-up and absolute changes in cardiac biomarkers were clinically insignificant. There were no significant associations between soluble urokinase plasminogen activator receptor and these markers of cardiotoxicity (all p > 0.05).

CONCLUSIONS

In this breast cancer cohort, doxorubicin treatment was associated with a very low risk for cardiotoxicity. Across this narrow range of clinical endpoints, soluble urokinase plasminogen activator receptor was not associated with markers of subclinical cardiotoxicity. Further studies are needed to clarify the prognostic utility of soluble urokinase plasminogen activator receptor in doxorubicin-associated cardiomyopathy and should include a larger cohort of leukemia and lymphoma patients who receive higher doses of doxorubicin.

Comparison of gut microbiome composition in colonic biopsies, endoscopically-collected and at-home-collected stool samples

Aim

The goal of this study is to compare microbiome composition in three different sample types in women, namely stool brought from home vs. solid stool samples obtained at the time of an unprepped sigmoidoscopy vs. biopsies of the colonic mucosa at the time of an unprepped sigmoidoscopy, using alpha- and beta-diversity metrics following bacterial 16S rRNA sequencing. The findings may have relevance to health and disease states in which bacterial metabolism has a significant impact on molecules/metabolites that are recirculated between the gut lumen and mucosa and systemic circulation, such as estrogens (as in breast cancer) or bile acids.

Methods

Concomitant at-home-collected stool, endoscopically-collected stool, and colonic biopsy samples were collected from 48 subjects (24 breast cancer, 24 control.) After 16S rRNA sequencing, an amplicon sequence variant (ASV) based approach was used to analyze the data. Alpha diversity metrics (Chao1, Pielou's Evenness, Faith PD, Shannon, and Simpson) and beta diversity metrics (Bray-Curtis, Weighted and Unweighted Unifrac) were calculated. LEfSe was used to analyze differences in the abundance of various taxa between sample types.

Results

Alpha and beta diversity metrics were significantly different between the three sample types. Biopsy samples were different than stool samples in all metrics. The highest variation in microbiome diversity was noted in the colonic biopsy samples. At-home and endoscopically-collected stool showed more similarities in count-based and weighted beta diversity metrics. There were significant differences in rare taxa and phylogenetically-diverse taxa between the two types of stool samples. Generally, there were higher levels of Proteobacteria in biopsy samples, with significantly more Actinobacteria and Firmicutes in stool (all p < 0.001, q-value < 0.05). Overall, there was a significantly higher relative abundance of Lachnospiraceae and Ruminococcaceae in stool samples (at-home collected and endoscopically-collected) and higher abundances of Tisserellaceae in biopsy samples (all p < 0.001, q-value < 0.05).

Conclusion

Our data shows that different sampling methods can impact results when looking at the composition of the gut microbiome using ASV-based approaches.

Abstract P5-16-02: Updated efficacy, safety and translational data from MARIO-3, a phase II open-label study evaluating a novel triplet combination of eganelisib (IPI-549), atezolizumab (atezo), and nab-paclitaxel (nab-pac) as first-line (1L) therapy for locally advanced or metastatic triple-negative breast cancer (TNBC)

Background: Eganelisib is a first-in-class, oral, immuno-oncology macrophage reprogramming agent. The IMpassion130 randomized trial in 1L advanced TNBC has demonstrated improved efficacy with the addition of atezo to nab-pac in patients with PD-L1+ tumors. Adding eganelisib to the approved doublet of atezo and nab-pac is expected to improve patient benefit regardless of PD-L1 status. Methods: Eligible patients (pts) had measurable unresectable locally advanced or metastatic TNBC and no prior systemic therapy for advanced disease. A safety run-in assessed the safety of the triplet of oral eganelisib 30 mg daily in combination with IV nab-pac 100 mg/m2 given on days 1, 8, & 15, and IV atezo 840 mg given on days 1 & 15 of a 28 day cycle. After establishing tolerability and confirmation of the 30 mg dose in the safety run-in (n=6), the expansion phase of the phase II study was initiated to enroll approximately 60 pts (30 PD-L1+ and 30 PD-L1-). Cycles are repeated until loss of clinical benefit, unacceptable toxicity or consent withdrawal. The primary efficacy endpoint is confirmed complete response (CR) rate per RECIST v1.1. Secondary endpoints include the overall response rate (ORR), progression free survival and safety assessment. Results: As of 6/26/2021, data from the safety run-in and the expansion cohorts are reported for 43 pts evaluable for safety and 38 evaluable for efficacy defined as having at least one post-baseline tumor assessment. 2 CRs (2/38), 19 PRs (19/38), and 11 SDs (11/38) were observed with an ORR of 55.3% (21/38) and a disease control rate (DCR) of 84.2% (32/38). Responses were seen irrespective of PD-L1 status; in PD-L1+ pts, ORR is 66.7% (8/12) and DCR is 91.7% (11/12), and in PD-L1- pts, ORR is 47.8% (11/23) and DCR is 78.3% (18/23). The most common all-grade adverse events were nausea (51.2%), fatigue (48.8%), alopecia (32.6%), diarrhea (32.6%), rash maculo-papular (30.2%), ALT increased (27.9%), and AST increased (25.6%). The most common grade ≥3 adverse events were ALT increased (18.6%), AST increased (14.0%), neutrophil count decreased (9.3%) and rash maculo-papular (9.3%). The safety profile is acceptable and in line with expectations of component drugs with no additive or new safety signals. Translational data from paired biopsies show a shift in tumor associated macrophages towards an immune activated state as well as an increase in cytotoxic T cells. In addition, a subset of tumors with baseline PD-L1 negative status show conversion to PD-L1 positive status post treatment. Consistent with immune activation, increased interferon gamma signature, increased proinflammatory cytokines and T cell invigoration were observed in peripheral blood cells. Conclusions: The novel triplet regimen of eganelisib, atezo, and nab-pac shows promising anti-tumor activity (ORR 55.3% and DCR 84.2%) irrespective of PD-L1 status and has manageable toxicity. . Translational data from paired biopsies and peripheral blood show evidence of immune activation regardless of PD-L1 status as well as conversion from PD-L1 negative to PD-L1 positive subtype within a subset of patients treated with the triplet regimen. The expansion phase of the phase II study is currently enrolling. At the time of presentation, we will have updated efficacy, safety and translational data.

Citation Format: Soliman Hatem, Jeffrey Hargis, Anthony Elias, Arielle Lee, Rachel Swart, Shaker Dahkil, Alexandra Drakaki, Vu Phan, Frederic Kass, Melody Cobleigh, Sanil Babu, Katherine Tkaczuk, Brenda O'Connell, Jennifer Roberts, Nora Zizlsperger, Erika Hamilton. Updated efficacy, safety and translational data from MARIO-3, a phase II open-label study evaluating a novel triplet combination of eganelisib (IPI-549), atezolizumab (atezo), and nab-paclitaxel (nab-pac) as first-line (1L) therapy for locally advanced or metastatic triple-negative breast cancer (TNBC) [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 P5-16-02.

Abstract P2-13-07: Zanidatamab (ZW25), a HER2-targeted bispecific antibody, in combination with chemotherapy (chemo) for HER2-positive breast cancer (BC): Results from a phase 1 study

Background: Despite the availability of multiple HER2-targeted therapies, most patients (pts) with advanced HER2-positive BC experience disease progression, and an unmet medical need remains. Zanidatamab (zani) binds to HER2 across a range of expression levels and induces formation of receptor clusters, resulting in receptor internalization and downregulation that affect signal transduction. Zani potently activates antibody-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis, and complement-dependent cytotoxicity. In this ongoing phase 1 study (NCT02892123), data from BC pts treated with zani monotherapy have been previously reported. Here, we evaluated the safety and antitumor activity of zani in combination with chemo in HER2-positive BC pts. Methods: Pts with locally advanced and/or metastatic HER2-positive (immunohistochemistry [IHC] 3+ or IHC 2+/fluorescence in situ hybridization+) BC who received prior trastuzumab (tras), pertuzumab (pert), and T-DM1 were enrolled. Eligibility criteria included Eastern Cooperative Oncology Group performance status ≤1 and adequate organ function. Prior history of treated stable brain metastases was allowed. Zani (20 mg/kg Q2W or 30 mg/kg Q3W) was administered in combination with paclitaxel (pac), capecitabine (cap), or vinorelbine (vin). Zani + chemo was continued until disease progression or toxicity; if chemo was discontinued due to toxicity, zani treatment could be continued. Primary endpoints were safety and tolerability assessments; secondary efficacy endpoints included objective response rate (ORR) and disease control rate (DCR; complete response [CR] + partial response [PR] + stable disease [SD]) per RECIST v1.1, and progression-free survival (PFS). Clinical benefit rate (CBR) was defined as SD ≥24 weeks or best overall response of CR or PR. Results: As of 3 May 2021, 20 HER2-positive BC pts had enrolled (zani + pac, n=4; zani + cap, n=9; zani + vin, n=7). Ten pts were hormone receptor positive (data available for 19 pts), and 7 pts had a prior history of brain metastases. Median age was 53 years (range, 38-72), with median prior systemic therapies of 4.5 (range, 2-7) and median of 2 regimens in the metastatic setting. Pts received a median of 3 prior HER2 regimens; all pts received tras and T-DM1, 17 received pert, and 6 received tyrosine kinase inhibitors. In the 16 response evaluable (measurable disease and either post-baseline assessments or earlier death/progression) pts, confirmed ORR was 37.5% (with 1 additional response pending confirmation), CBR was 50%, and DCR was 81.3%. Median duration of response was not reached (range, 1.8+ to 16.8+ mo), with 4 of 6 confirmed responses ongoing. Among all pts (n=20), the most common (≥30% of pts) zani- and/or chemo-related adverse events (AEs) were diarrhea (65%), nausea (45%), peripheral neuropathy (35%), and fatigue (30%). One pt experienced grade 3 diarrhea leading to dose reduction of zani, and 1 pt discontinued zani due to AEs (abdominal pain and nausea, both grade ≤2). Four grade 4 AEs were observed in 4 (20%) pts: neutrophil count decreased (2 pts) and neutropenia (1 pt), all related to chemo, and hyponatremia (1 pt, not related to study treatment). Serious AEs were observed in 2 (10%) pts (pleural effusion, 1 pt; pneumonitis and upper respiratory tract infection, 1 pt), none related to zani. No grade 5 AEs were reported. Conclusions: Zani in combination with chemo is well tolerated, with encouraging and durable antitumor activity in heavily pretreated (including prior tras, pert, and T-DM1) pts with HER2-positive BC. These data support further investigation of zani as a novel therapeutic for these pts. The cap and vin cohorts continue to enroll, and additional cohorts are evaluating zani ± chemo in combination with tucatinib.

Citation Format: Philippe L Bedard, Seock-Ah Im, Elena Elimova, Sun Young Rha, Rachel Goodwin, Cristiano Ferrario, Keun-Wook Lee, Diana Hanna, Funda Meric-Bernstam, Jose Mayordomo, Murali Beeram, Erika Hamilton, Jorge Chaves, Melody Cobleigh, Tony Mwatha, Joseph Woolery, Do-Youn Oh. Zanidatamab (ZW25), a HER2-targeted bispecific antibody, in combination with chemotherapy (chemo) for HER2-positive breast cancer (BC): Results from a phase 1 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 P2-13-07.

Abstract P3-08-04: The genomic and transcriptomic landscape of PIK3R1 mutated breast cancers

Background: Human breast cancers may harbor pathogenic somatic alterations in PIK3R1, which encodes the regulatory subunit—p85a—of the PI3K signaling complex. Prior studies developed an isogenic cellular system lacking p85a and investigated therapeutic approaches for breast cancers that lack functional p85a. For instance, somatic loss of PIK3R1 may sensitize breast cancer cells to MEK inhibition; work in patient-derived xenograft models confirmed this observation. Here, we wanted to investigate the significance of PIK3R1 mutations (PIK3R1MUT) in human breast cancer by using real-world data to characterize the genomic landscape of breast cancer patients with PIK3R1MUT. Additionally, our methodology allows us to assess the effect of PIK3R1MUT on corresponding mRNA expression-levels, tumor mutational burden (TMB), and microsatellite instability (MSI) to better understand the molecular-level effects of this important gene. Methods: We used the Tempus LENS platform to retrospectively analyze next-generation sequencing (NGS) data from 3400 HER2-negative (HER2-) advanced or metastatic breast cancer patients with confirmed hormone receptor status (HR+/-). Our cohort consisted of molecularly profiled, deidentified breast cancer cases using the Tempus xT solid tumor assay (DNA-seq of 595-648 genes at 500x coverage, and full transcriptome RNA-seq). This assay assesses mutations in both germline and somatic tissue, and characterizes nucleotide variants, insertions/deletions, and copy number variations. Results: The prevalence of PIK3R1MUT in HER2- breast cancer was 2.3% (77/3400). PIK3R1MUT occurred more frequently than expected in HR- breast cancer relative to the proportion we observed for wild-type PIK3R1 (Chi-squared test, p&lt;0.001). In the HR+ subtype, high TMB (defined as 10 mutations/MB) occurred more frequently in PIK3R1MUT tumors than in samples with wild-type PIK3R1 (PIK3R1WT) status (Fisher’s exact test, p=0.039). Further, MSI-high status was absent in PIK3R1MUT tumors but was observed in PIK3R1WT samples. We assessed co-mutational patterns and found that pathogenic or likely pathogenic mutations in PTEN, TP53. and NF1 were more frequent in PIK3R1MUT samples, whereas mutations in PIK3CA were more frequent in the PIK3R1WT cohort (Table 1). At the transcriptional-level, PIK3R1 expression was similar in HR+ samples regardless of PIK3R1 mutational status but PIK3R1 transcript expression was significantly higher among PIK3R1MUT samples (Wilcoxon rank-sum test, p&lt;0.001). Conclusions: Our study used real-world evidence to build on previous pre-clinical studies, and illustrates the importance of PIK3R1MUT in breast cancer. We found that certain mutations associated with poor outcomes and endocrine therapy resistance (e.g., PTEN, and NF1) were more frequent in PIK3R1MUT tumor samples. Interestingly, we did not find evidence that PIK3R1MUT results in decreased PIK3R1 mRNA expression but instead observed that in the HR- subtype PIK3R1MUT gene expression was significantly higher. Overall, this study shows that PIK3R1 may be an important therapeutic target in breast cancer.

Table 1.- Co-mutations and PIK3R1 transcript abundance in PIK3R1MUT vs PIK3R1WT samples.Correlation of Gene Co-mutations with PIK3R1MUTGenesPIK3R1MUT (n=77)n (%)PIK3R1WT (n=3323)n (%)p-valuePositively correlatedPTEN21 (27%)176 (5.3%)&lt;0.001NF113 (17%)134 (4.0%)&lt;0.001TP5344 (57%)1289 (39)0.001Negatively CorrelatedPIK3CA9 (12%)861 (26%)0.005PIK3R1 gene expressionSub-typeNormalized expressionNormalized expressionp-valueHR+3.34 (n=30)3.28 (n=1720)0.2HR-3.45 (n=33)3.23 (n=678)&lt;0.001

Citation Format: Melody Cobleigh, Emmanuel Okeke, Brett Mahon, Elizabeth Mauer, Alex Barrett, Abde Abukhdeir. The genomic and transcriptomic landscape of PIK3R1 mutated breast cancers [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 P3-08-04.

The phase II MutHER study of neratinib alone and in combination with fulvestrant in HER2 mutated, non-amplified metastatic breast cancer

PURPOSE

HER2 mutations (HER2^mut) induce endocrine resistance in estrogen receptor positive (ER+) breast cancer.

EXPERIMENTAL DESIGN

In this single arm multi-cohort phase II trial, we evaluated the efficacy of neratinib plus fulvestrant in patients with ER+/HER2^mut, HER2-non-amplified metastatic breast cancer (MBC) in the fulvestrant-treated (n=24) or fulvestrant-naïve cohort (n=11). Patients with ER-negative/HER2^mut MBC received neratinib monotherapy in an exploratory ER- cohort (n=5).

RESULTS

The clinical benefit rate (CBR: 95% CI) was 38% (18-62%), 30% (7-65%), and 25% (1-81%) in the fulvestrant-treated, fulvestrant-naïve, and ER- cohort, respectively. Adding trastuzumab at progression in 5 patients resulted in 3 partial responses and 1 stable disease {greater than or equal to}24 weeks. CBR appeared positively associated with lobular histology and negatively associated with HER2 L755 alterations. Acquired HER2^mut were detected in 5 of 23 patients at progression.

CONCLUSION

Neratinib and fulvestrant is active for ER+/HER2^mut MBC. Our data supports further evaluation of dual HER2 blockade for the treatment of HER2^mut MBC.

Abstract CT026: A phase II trial of neratinib (NER) or NER plus fulvestrant (FUL) (N+F) in HER2 mutant, non-amplified (HER2mut) metastatic breast cancer (MBC): Part II of MutHER

Introduction: The irreversible pan-HER inhibitor NER showed modest single agent activity for HER2mut MBC in Part I of MutHER trial. In Part II, we hypothesized that (1) N+F would improve activity in estrogen receptor positive (ER+) HER2mut MBC due to ER-HER2 crosstalk and (2) dual HER2 blockade by adding trastuzumab at disease progression (PD) could overcome resistance.

Methods: Pts with ER+HER2mut MBC were enrolled to 2 cohorts (FUL treated or naive) to receive N+F with diarrhea prophylaxis. ER- pts received NER in an exploratory ER- cohort. Trastuzumab was added at PD if approved by insurance. Simon's Minimax 2-stage phase II design with the primary endpoint of clinical benefit rate (CBR: rates of complete/partial response [CR/PR] plus stable disease [SD] &gt;24 weeks [wks]), with anticipated vs null hypothesis being CBR of 55% vs 35% (FUL treated) or 65% vs 40% (FUL naïve) with 80% power, 1 sided 0.05 alpha, was used. Secondary endpoints included progression free survival (PFS) and adverse events (AEs). Serial blood samples were analyzed for circulating tumor DNA (ctDNA) by Guardant360 for concomitant mutations, HER2mut variant allele frequency (VAF) dynamics, and resistance mechanisms.

Results: Between Sep. 2015 and Oct. 2020, 40 pts with HER2mut MBC were enrolled, completing the 1st stage of each ER+ cohort. 35 pts (21 FUL treated, 10 FUL naïve, 4 ER-) were evaluable for response, with median age 63 (35-82) years, 3 (0-12) prior MBC regimen, lobular BC in 13 (37%) and visceral mets in 32 (91%) pts. 21 (68%) ER+ pts had prior CDK4/6 inhibitor. All but 1 pt has come off study due to PD. Table 1 shows the efficacy by cohort. Further enrollment is closed per protocol. Adding trastuzumab at PD induced CB in 4 (3 PR, 1 SD≥24 wks) of 5 pts (1 ER-, 4 ER+), with PFS 28 (95% CI 18~NA) wks. Common AEs across cohorts were diarrhea (G3 21%) and fatigue (G3 5%). No G4 AEs.

ctDNA HER2mut was detected in 72% (23/32) baseline (BL) samples tested. In pts with paired samples, HER2mut VAF decreased at C1D15/C2D1 from BL in 75% (15/20) and rose in 89% (16/18) at PD. Acquired HER2mut, including the T798I gatekeeper mutation, were detected in 2 pts at PD. Mutations in TP53 (53%), PIK3CA (43%), and CDH1 (35%) were common, but none significantly associated with PFS in all or ER+ pts.

Conclusions: NER, or N+F, is active for HER2mut MBC with good tolerability. Adding trastuzumab at PD induced further response, supporting dual HER2 blockade for HER2mut MBC.

Table 1.EfficacyCohortFUL treatedFUL naïveER-Best Response, n evaluablen = 21n = 10n = 4CR, n100PR, n431SD (≥ 24 wks), n300SD (&lt; 24 wks), n1030PD, n343CBR, n with CB/total n evaluable, % (95% CI)8 of 20*, 40% (19~64%)3 of 10, 30% (7~65%)1 of 4, 25% (0.6~81%)mPFS (95% CI), wks, ITT (n)24 (16~31) wks, (n = 24)20 (8~NA) wks, (n = 11)8.5 (8~NA) wks, (n = 5)*20 of 21 pts are evaluable for CBR in the FUL treated Cohort as 1 pt had SD as best response and treatment is still ongoing. ITT (intent to treat) population is used for mPFS estimate.

Citation Format: Cynthia X. Ma, Jingqin Luo, Rachel A. Freedman, Timothy Pluard, Julie Nangia, Janice Lu, Frances Valdez-Albini, Melody Cobleigh, Jason Jones, Nancy U. Lin, Eric Winer, P. Kelly Marcom, Shana Thomas, Jill Anderson, Brittney Haas, Kimberly M. Hamann, Richard Bryce, Alshad S. Lalani, Lisa Carey, Matthew Goetz, Feng Gao, Gretchen Kimmick, Mark Pegram, Matthew J. Ellis, Ron Bose. A phase II trial of neratinib (NER) or NER plus fulvestrant (FUL) (N+F) in HER2 mutant, non-amplified (HER2mut) metastatic breast cancer (MBC): Part II of MutHER [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT026.

Baseline characteristics and first-line treatment patterns in patients with HER2-positive metastatic breast cancer in the SystHERs registry

BACKGROUND

Systemic Therapies for HER2-Positive Metastatic Breast Cancer Study (SystHERs, NCT01615068) was a prospective, observational disease registry designed to identify treatment patterns and clinical outcomes in patients with HER2-positive metastatic breast cancer (MBC) in real-world treatment settings.

METHODS

SystHERs enrolled patients aged ≥ 18 years with recently diagnosed HER2-positive MBC. Treatment regimens and clinical management were determined by the treating physician. In this analysis, patients were compared descriptively by first-line treatment, age, or race. Multivariate logistic regression was used to examine the associations between baseline variables and treatment selections. Clinical outcomes were assessed in patients treated with trastuzumab (Herceptin [H]) + pertuzumab (Perjeta [P]).

RESULTS

Patients were enrolled from June 2012 to June 2016. As of February 22, 2018, 948 patients from 135 US treatment sites had received first-line treatment, including HP (n = 711), H without P (n = 175), or no H (n = 62) (with or without chemotherapy and/or hormonal therapy). Overall, 68.7% received HP + taxane and 9.3% received H without P + taxane. Patients aged < 50 years received HP (versus H without P) more commonly than those ≥ 70 years (odds ratio 4.20; 95% CI, 1.62-10.89). Chemotherapy was less common in patients ≥ 70 years (68.2%) versus those < 50 years (88.0%) or 50-69 years (87.4%). Patients treated with HP had median overall survival of 53.8 months and median progression-free survival of 15.8 months.

CONCLUSIONS

Our analysis of real-world data shows that most patients with HER2-positive MBC received first-line treatment with HP + taxane. However, older patients were less likely to receive dual HER2-targeted therapy and chemotherapy.

Abstract PD3-08: Tucatinib vs placebo in combination with trastuzumab and capecitabine for patients with locally advanced unresectable or HER2-positive metastatic breast cancer (HER2CLIMB): Outcomes by hormone receptor status

Background Tucatinib (TUC) is a highly selective oral tyrosine kinase inhibitor of HER2 with minimal inhibition of EGFR. It was recently approved by the FDA for patients (pts) with HER2+ metastatic breast cancer (MBC), including pts with brain metastases (BM) whose cancers have progressed on at least 1 prior anti-HER2 regimen in the metastatic setting. In the HER2CLIMB (NCT02614794) pivotal trial, pts with HER2+ MBC previously treated with trastuzumab (T), pertuzumab, and trastuzumab emtansine (T-DM1) were randomized to receive TUC or placebo in combination with T and capecitabine (C). The addition of TUC resulted in clinically meaningful and statistically significant improvements in overall survival (OS), progression-free survival (PFS), and objective response rate (ORR) in HER2+ MBC pts. Primary methods and outcomes have been reported previously (Murthy, NEJM 2019). Here we present an exploratory analysis describing the outcomes in the HER2CLIMB trial based on hormone receptor (HR) status.

Methods Pts were randomized 2:1 to receive TUC or placebo in combination with T and C. All pts had a baseline brain MRI and randomization was stratified by presence of BM, ECOG status, and geographic region. All pts with HER2+ MBC who were positive for either or both estrogen receptor and progesterone receptor (&gt; 1%) were assigned to the HR “positive” subgroup. Pts not meeting the above criteria were assigned to the HR “negative” subgroup. For the exploratory HR+/HR- efficacy analysis presented here, PFS per RECIST 1.1 by blinded independent central review was evaluated in the first 480 pts enrolled. OS, PFS in pts with baseline BM, and confirmed ORR in pts with measurable disease were evaluated in the total study population. P values presented for PFS are nominal.

Results Overall, 612 pts were enrolled to HER2CLIMB; 370 pts (60%) had HR+ and 242 (40%) had HR- tumors. Baseline demographics and disease characteristics in HR+/HR- subgroups were generally balanced between treatment arms. In the HR+ group, there was a 42% reduction in the risk of progression or death in the TUC arm (hazard ratio: 0.58; 95% CI: 0.42, 0.80; P=0.0008); median (95% CI) PFS was 7.6 mo (7.4, 9.5) in the TUC arm vs 5.6 mo (4.3, 7.4) in the control arm. In the HR- group, there was a 46% reduction in the risk of progression or death in the TUC arm (hazard ratio: 0.54; 95% CI: 0.34, 0.86; P=0.008); median (95% CI) PFS was 8.1 mo (7.0, 11.6) in the TUC arm vs 4.2 mo (3.1, 8.6) in the control arm. In the total population, median OS was 21.7 mo vs 18.2 mo in HR+ in the TUC arm vs control arm, respectively; median OS in HR- was 31.1 mo in the TUC arm vs 14.1 mo in the control arm. In pts with BM in the HR+ group (n=166 [45%]), there was a 52% reduction in the risk of progression or death (hazard ratio: 0.48; 95% CI: 0.31, 0.75; P=0.0008); median (95% CI) PFS was 7.5 mo (5.6, 9.5) in the TUC arm vs 5.1 mo (4.1, 5.7) in the control arm, and median OS was 18.1 mo vs 12.8 mo, respectively. In pts with BM in the HR- group (n=125 [52%]), there was a 50% reduction in the risk of progression or death (hazard ratio: 0.50; 95% CI: 0.27, 0.95; P=0.03); median (95% CI) PFS was 7.8 mo (6.1, 11.6) in the TUC arm vs 5.4 mo (2.9, 8.6) in the control arm, and median OS was 18.5 mo vs 11.5 mo, respectively. In the total population, ORR was numerically higher in the TUC arm vs the control arm regardless of HR status (HR+: 37.4% [95% CI: 30.8, 44.5] vs 27.1% [95% CI: 19.0, 36.6], respectively and HR-: 45.3% [95% CI: 36.7, 54.0] vs 15.6% [95% CI: 7.8, 26.9], respectively).

Conclusions Among pts with HER2+ MBC previously treated with T, pertuzumab, and T-DM1, the addition of TUC to T and C showed clinically meaningful improvements of PFS, OS, and ORR independent of HR status. Furthermore, pts with HR+ and HR- MBC with BM derived similar benefit from the addition of TUC to T and C.

Citation Format: Erika Hamilton, Mattea Reinisch, Sherene Loi, Alicia Okines, Paula R. Pohlmann, Eva Harder Brix, Hugues Bourgeois, Belinda Yeo, Cheryl Aylesworth, Melody Cobleigh, Anthony Goncalves, Rebecca Moroose, Katherine H.R. Tkaczuk, Michaela Tsai, Christine Simmons, Michael Andersson, Hatem Soliman, Michelina Cairo, Lisa A. Carey, David Cameron, Jorge Ramos, Wentao Feng, Mafalda Oliveira. Tucatinib vs placebo in combination with trastuzumab and capecitabine for patients with locally advanced unresectable or HER2-positive metastatic breast cancer (HER2CLIMB): Outcomes by hormone receptor status [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 PD3-08.

Paired tumor sequencing and germline testing in breast cancer management: An experience of a single academic center

BACKGROUND

Genetic testing for cancer predisposition is recommended to women with breast cancer who meet the criteria for such testing. After the FDA approvals of the poly ADP ribose polymerase (PARP) inhibitors, olaparib and talazoparib, for treatment of metastatic breast cancer, carrying germline mutations in BRCA1 and BRCA2 genes, the genetic testing result has become critical in their care. With the recent FDA approval of alpelisib for the treatment of PIK3CA-mutated hormone-receptor positive metastatic breast cancer, tumor molecular profiling to identify somatic mutations and potential molecularly targeted agents is increasingly utilized in the treatment of advanced breast cancer.

AIM

Combining germline and somatic sequencing (paired testing) offers an advantage over a single technique approach. Our study evaluates the role of paired testing on the management of breast cancer patients.

METHODS AND RESULTS

Forty-three breast cancer patients treated at Rush University Medical Center underwent paired germline and somatic variant testing in 2015 to 2017. A retrospective chart review was conducted with the analysis of demographic, clinical, and genomic data. Three actionable germline variants were found in the CHEK2 (2) and ATM (1) genes. 95% of tumors had somatic mutations. Seventy-seven percent of tumors had genomic alterations targetable with agents approved for breast cancer and 88% had molecular targets for agents approved for other cancers. Clinical examples of such use are described and potential future directions of tumor and paired testing are discussed.

CONCLUSIONS

Germline variants were present in a relatively small patient group not routinely tested for inherited alterations. Potentially targetable somatic alterations were identified in the majority of breast cancers. Paired testing is a feasible and efficient approach that delivers valuable information for the care of breast cancer patients and eliminates serial testing.

Baseline Characteristics, Treatment Patterns, and Outcomes in Patients with HER2-Positive Metastatic Breast Cancer by Hormone Receptor Status from SystHERs

PURPOSE

We report treatments and outcomes in a contemporary patient population with HER2-positive metastatic breast cancer (MBC) by hormone receptor (HR) status from the Systemic Therapies for HER2-positive Metastatic Breast Cancer Study (SystHERs).

EXPERIMENTAL DESIGN

SystHERs (NCT01615068) was an observational, prospective registry study of U.S.-based patients with newly diagnosed HER2-positive MBC. Endpoints included treatment patterns and clinical outcomes.

RESULTS

Of 977 eligible patients (enrolled from 2012 to 2016), 70.1% (n = 685) had HR-positive and 29.9% (n = 292) had HR-negative disease. Overall, 59.1% (405/685) of patients with HR-positive disease received any first-line endocrine therapy (with or without HER2-targeted therapy or chemotherapy); 34.9% (239/685) received HER2-targeted therapy + chemotherapy + sequential endocrine therapy. Patients with HR-positive versus HR-negative disease had longer median overall survival (OS; 53.0 vs 43.4 months; hazard ratio, 0.70; 95% confidence interval, 0.56-0.87). Compared with patients with high HR-positive staining (10%-100%, n = 550), those with low HR-positive staining (1%-9%, n = 60) received endocrine therapy less commonly (64.2% vs 33.3%) and had shorter median OS (53.8 vs 40.1 months). Similar median OS (43.4 vs 40.1 months) was observed in patients with HR-negative versus low HR-positive tumors (1%-9%).

CONCLUSIONS

Despite evidence that first-line HER2-targeted therapy, chemotherapy, and sequential endocrine therapy improves survival in patients with HR-positive, HER2-positive disease, only 34.9% of patients in this real-world setting received such treatment. Patients with low tumor HR positivity (1%-9%) had lower endocrine therapy use and worse survival than those with high tumor HR positivity (10%-100%).

Abstract P5-06-24: Validation of the Johns Hopkins oncotype DX recurrence score estimator

Objective

Oncotype DX (ODX) is a 21-gene assay used to predict the benefit of adjuvant chemotherapy in hormone receptor-positive, HER2-negative, lymph node-negative breast cancer. However, the test is expensive and the incremental contribution of this assay to routinely available clinicopathological information and how to integrate that information to best inform clinical decision making is unknown. Several models have been developed to predict whether there are cases in which a clinician or patient could opt to forgo ODX because the outcome of the test might be predicted with a high degree of accuracy using routinely available measures. One such model was developed and validated at Johns Hopkins University. Here we used their recurrence score estimator to learn whether we could safely adopt the calculator for use at our institution to improve resource utilization.

Methods

An IRB-approved prospective database was created in 2010 for patients seen by a single medical oncologist at Rush University Medical Center and for whom oncotype DX was performed. From this database, patients were identified with HR+, HER2-negative, node-negative breast cancer and for whom age at diagnosis, tumor size, grade and Ki-67 were known. These data were entered into the Johns Hopkins breast cancer recurrence score estimator (http://www.breastrecurrenceestimator.onc.jhmi.edu). This model categorizes patients with a recurrence score (RS) of less than or equal to 25 as low risk and those with a score of greater than 25 as high risk.

Results

There were 189 patients. The mean age, tumor size, ER%, PR% and Ki-67% were 58 years old, 1.5 cm, 88%, 44% and 15% respectively. 14% had a RS greater than 25. The estimator assigned 65 patients to low risk, 59 of whom had a low RS and 6 with a high RS. The estimator assigned 4 patients to high risk, all of whom had a high RS.

Conclusions

The Johns Hopkins recurrence score estimator assigned 69 patients to low or high risk with 91.3% accuracy. Future analysis of a larger sample size is needed to optimize the accuracy of this estimator nationally. It may also be beneficial to separately analyze patients aged 50 or younger with an ODX score between 16 and 25 who had chemotherapy benefit in the TAILORx study in order to improve the utility of this risk estimator.

Citation Format: Kristen Millado, Louis Fogg, Ritu Ghai, Melody Cobleigh. Validation of the Johns Hopkins oncotype DX recurrence score estimator [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-06-24.

Abstract B001: Safety and efficacy of ZW25, a HER2-targeted bispecific antibody, in combination with chemotherapy in patients with locally advanced and/or metastatic HER2-expressing gastroesophageal cancer

Background: Up to 30% of gastroesophageal adenocarcinoma (GEA) overexpress HER2. ZW25 is a novel bispecific antibody that targets HER2 domains ECD2 and ECD4, resulting in multiple differentiated and unique mechanisms of action, including increased antibody binding density and improved receptor internalization and downregulation relative to trastuzumab. In an ongoing phase 1 trial (ZWI-ZW25-101; NCT02892123), single-agent ZW25 was well tolerated and showed promising anti-tumor activity across HER2-expressing solid tumors. This abstract presents data for GEA patients treated with ZW25 in combination with chemotherapy in Study ZWI-ZW25-101. Methods Eligible patients had HER2-expressing (IHC 3+, IHC 2+/FISH+, or IHC 2+/FISH-) GEA and had disease progression after 1–3 lines of prior chemotherapy for advanced and/or metastatic disease. Fresh or archived tumor tissue was required for central review of HER2 status, although patients could be enrolled based on local results. Patients received ZW25 in combination with paclitaxel or capecitabine. Evaluations included standard safety assessments, tumor re-staging (Q8W by RECIST 1.1), and assessment of peak/trough pharmacokinetic (PK) levels during each cycle. Results To date, 14 patients have been enrolled, with safety and efficacy data available for 11. ZW25 was administered in combination with paclitaxel (n=5) or capecitabine (n=6). The median age was 62 yrs (range, 26-80). The median number of prior anti-cancer regimens was 3 and the median number of prior HER2-targeted therapies was 1. Six patients (55%) were HER2 IHC3+ or IHC2+ and FISH+ per central review. The most common adverse events (AEs) considered related to ZW25 or ZW25 and chemotherapy were diarrhea (n=5; 45%), fatigue (n=3; 27%), and nausea (n=3; 27%); the majority of events were Grade 1 or 2. Grade 3 or higher events considered related to ZW25 or ZW25 and chemotherapy occurred in 3 patients (27%), including fatigue, hypokalemia, and neutropenia (n=1 each). One additional patient experienced a Grade 5 serious adverse event of pneumonitis, reported as related to the combination of ZW25 and paclitaxel. This patient had been previously treated with trastuzumab, cisplatin, and capecitabine; pembrolizumab and margetuximab; and most recently DS8201, and had asymptomatic interstitial lung disease at study entry. A total of 9/11 patients (82%) had measurable disease and 8/9 (89%) were response-evaluable. The objective response rate was 63% (95% CI: 25, 92) (5/8 patients; all partial responses, with 4 confirmed to date) and the disease control rate was 75% (6/8 patients). Responses were seen in patients with FISH+ and FISH- disease, as well as in combination with either paclitaxel or capecitabine. Patients have received between 1 and 12 cycles of treatment and 4 patients remain on treatment. PK data will be presented at the meeting. Conclusions The combination of ZW25 with chemotherapy was generally well tolerated in heavily pre-treated patients with HER2 high- and low-expressing GEA and the preliminary anti-tumor activity is promising. Further evaluation of the safety and efficacy of ZW25 in combination with standard of care chemotherapy regimens has been initiated in frontline GEA (ZW25-201; NCT03929666).

Citation Format: Funda Meric-Bernstam, Jorge Chaves, Do-Youn Oh, Jeeyun Lee, Yoon-Koo Kang, Erika Hamilton, Jose Mayordomo, Melody Cobleigh, Christos Vaklavas, Elena Elimova, Jaffer Ajani, Jordi Rodon, Gerry Rowse, Todd Gray, Rose Lai, Diana Hanna. Safety and efficacy of ZW25, a HER2-targeted bispecific antibody, in combination with chemotherapy in patients with locally advanced and/or metastatic HER2-expressing gastroesophageal cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B001. doi:10.1158/1535-7163.TARG-19-B001

Influence of breast reconstruction on technical aspects of echocardiographic image acquisition compared with physician-assessed image quality

Introduction

Assessment of cardiac function after treatment for breast cancer relies on interval evaluation of ventricular function through echocardiography. Women who undergo mastectomy more frequently choose to undergo breast reconstruction with implant. This could impede assessment of cardiac function in those with left-sided implant. We aimed to examine whether left-sided breast reconstruction with tissue expanders (TE) affect echo image acquisition and quality, possibly affecting clinical decision-making.

Methods

A retrospective case-control study was conducted in 190 female breast cancer patients who had undergone breast reconstruction with TE at an urban academic center. Echocardiographic technical assessment and image quality were respectively classified as excellent/good or adequate/technically difficult by technicians; and excellent/good or adequate/poor by 2 board-certified cardiologist readers. Likelihood ratio was used to test multivariate associations between image quality and left-sided TE.

Results

We identified 32 women (81.3% white; mean age 48 years) with left-sided/bilateral TE, and 158 right-sided/no TE (76.6% white, mean age 57 years). In multivariable analyses, we found a statistically significant difference in technician-assessed difficulty in image acquisition between cases and controls (p = 0.01); but no differences in physician-assessed image quality between cases and controls (p = 0.09, Pearson’s r = 0.467).

Conclusions

Left-sided breast TE appears to affect the technical difficulty of echo image acquisition, but not physician-assessed echo image quality. This likely means that echo technicians absorb most of the impediments associated with imaging patients with breast TE such that the presence of TE has no bearing on downstream clinical decision-making associated with echo image quality.

De Novo Versus Recurrent HER2-Positive Metastatic Breast Cancer: Patient Characteristics, Treatment, and Survival from the SystHERs Registry

Background

Limited data exist describing real‐world treatment of de novo and recurrent HER2‐positive metastatic breast cancer (MBC).

Materials and Methods

The Systemic Therapies for HER2‐Positive Metastatic Breast Cancer Study (SystHERs) was a fully enrolled (2012–2016), observational, prospective registry of patients with HER2‐positive MBC. Patients aged ≥18 years and ≤6 months from HER2‐positive MBC diagnosis were treated and assessed per their physician's standard practice. The primary endpoint was to characterize treatment patterns by de novo versus recurrent MBC status, compared descriptively. Secondary endpoints included patient characteristics, progression‐free and overall survival (PFS and OS, by Kaplan‐Meier method; hazard ratio [HR] and 95% confidence interval [CI] by Cox regression), and patient‐reported outcomes.

Results

Among 977 eligible patients, 49.8% (n = 487) had de novo and 50.2% (n = 490) had recurrent disease. A higher proportion of de novo patients had hormone receptor–negative disease (34.9% vs. 24.9%), bone metastasis (57.1% vs. 45.9%), and/or liver metastasis (41.9% vs. 33.1%), and a lower proportion had central nervous system metastasis (4.3% vs. 13.5%). De novo patients received first‐line regimens containing chemotherapy (89.7%), trastuzumab (95.7%), and pertuzumab (77.8%) more commonly than recurrent patients (80.0%, 85.9%, and 68.6%, respectively). De novo patients had longer median PFS (17.7 vs. 11.9 months; HR, 0.69; 95% CI, 0.59–0.80; p < .0001) and OS (not estimable vs. 44.5 months; HR, 0.55; 95% CI, 0.44–0.69; p < .0001).

Conclusion

Patients with de novo versus recurrent HER2‐positive MBC exhibit different disease characteristics and survival durations, suggesting these groups have distinct outcomes. These differences may affect future clinical trial design. Clinical trial identification number. NCT01615068 (http://clinicaltrials.gov).

Implications for Practice

SystHERs was an observational registry of patients with HER2‐positive metastatic breast cancer (MBC), which is a large, modern, real‐world data set for this population and, thereby, provides a unique opportunity to study patients with de novo and recurrent HER2‐positive MBC. In SystHERs, patients with de novo disease had different baseline demographics and disease characteristics, had superior clinical outcomes, and more commonly received first‐line chemotherapy and/or trastuzumab versus those with recurrent disease. Data from this and other studies suggest that de novo and recurrent MBC have distinct outcomes, which may have implications for disease management strategies and future clinical study design.

The SystHERs breast cancer study was a fully enrolled, prospective registry study that explored contemporary treatment patterns and outcomes in patients with HER2‐positive metastatic breast cancer (MBC), resulting in one of the largest real‐world datasets for this population and providing a unique opportunity to assess patients with de novo and recurrent HER2‐positive MBC. This article reports baseline characteristics, treatment patterns, patient‐reported outcomes, and clinical outcomes in these patient subsets.

Somatic variants of potential clinical significance in the tumors of BRCA phenocopies

Background

BRCA phenocopies are individuals with the same phenotype (i.e. cancer consistent with Hereditary Breast and Ovarian Cancer syndrome = HBOC) as their affected relatives, but not the same genotype as assessed by blood germline testing (i.e. they do not carry a germline BRCA1 or BRCA2 mutation). There is some evidence of increased risk for HBOC-related cancers in relatives of germline variant carriers even though they themselves test negative for the familial variant (BRCA non-carriers). At this time, BRCA phenocopies are recommended to undergo the same cancer surveillance as individuals in the general population. This raises the question of whether the increased cancer risk in BRCA non-carriers is due to alterations (germline, somatic or epigenetic) in other cancer-associated genes which were not analyzed during BRCA analysis.

Methods

To assess the nature and potential clinical significance of somatic variants in BRCA phenocopy tumors, DNA from BRCA non-carrier tumor tissue was analyzed using next generation sequencing of 572 cancer genes. Tumor diagnoses of the 11 subjects included breast, ovarian, endometrial and primary peritoneal carcinoma. Variants were called using FreeBayes genetic variant detector. Variants were annotated for effect on protein sequence, predicted function, and frequency in different populations from the 1000 genomes project, and presence in variant databases COSMIC and ClinVar using Annovar.

Results

None of the familial BRCA1/2 mutations were found in the tumor samples tested. The most frequently occurring somatic gene variants were ROS1(6/11 cases) and NUP98 (5/11 cases). BRCA2 somatic variants were found in 2/6 BRCA1 phenocopies, but 0/5 BRCA2 phenocopies. Variants of uncertain significance were found in other DNA repair genes (ERCC1, ERCC3, ERCC4, FANCD2, PALB2), one mismatch repair gene (PMS2), a DNA demethylation enzyme (TET2), and two histone modifiers (EZH2, SUZ12).

Conclusions

Although limited by a small sample size, these results support a role of selected somatic variants and epigenetic mechanisms in the development of tumors in BRCA phenocopies.

Abstract PD8-12: Safety and efficacy of palbociclib and radiotherapy in metastatic breast cancer patients: Initial results of a novel combination

Purpose: Palbociclib is a selective CDK4/6 inhibitor approved for the treatment of metastatic ER+/HER2- breast cancer. Inhibition of CDK4/6 prevents cell cycle progression from G1 to the more radioresistant S phase, raising the possibility of an enhanced therapeutic effect if combined with radiotherapy (RT). Despite this potential benefit, clinicians seldom use this combination due to fear that RT may exacerbate palbociclib toxicity, particularly leukopenia. Our aim is to report the preliminary results of patients with metastatic breast cancer who received RT while receiving palbociclib.

Methods: We retrospectively reviewed records of all patients who were treated with palbociclib at our institution from 2015-2018. Patients who received RT for symptomatic metastases concurrently or within 14 days of last drug administration were included in our analysis. Local treatment effect was assessed by clinical exam and subsequent CT or MRI imaging, if applicable. Toxicity was graded based on CTCAE v5.0.

Results: A total of 16 females received palliative RT in association with palbociclib. The median age of the treated patients was 59.6 (range 33.3-91.0) years. The median time of closest palbociclib use to RT administration was 5 (range 0-14) days.

The following sites were treated in order of frequency: bone (10-axial skeleton [8-vertebra]; 1-ilium), brain (4: 3-WBRT & 1-SRS), and mediastinum (1). RT dose/fractionation for bone was 30 Gy/10 fxn (7), 35 Gy/14 fxn (2), 37.5 Gy/15 fxn (1), and 18 Gy/1 fxn (1). WBRT dose/fractionation was 30 Gy/10 fxn for all patients. SRS brain dose was 25 Gy/5 fxn. The patient treated to the mediastinum received 36 Gy/18 fxn.

At most recent follow-up, 12 patients are still living. The median time from RT to last known follow-up or death is 10.3 (range 1.7-29.6) months. Pain relief was achieved in 15 of 16 (93.8%) patients. No radiographic local failure was noted in the 13 patients with evaluable follow-up imaging.

The combination of RT and palbociclib was well-tolerated. Grade 1 fatigue, dermatitis, and nausea was noted in 5, 3, and 1 patient, respectively. One patient with WBRT developed Grade 1 headache. Six of 16 patients were leukopenic prior to RT initiation. Following RT, 7 patients were observed to have a drop in WBC count, of which 2 dropped into the leukopenic range. Only a total of 5 patients were leukopenic following RT, of which 3 were leukopenic before receiving RT. No acute or late Grade 2 or higher cutaneous, neurological, gastrointestinal, or hematologic toxicities were noted.

Conclusions: The use of RT in patients receiving palbociclib resulted in minimal Grade 1 and no Grade 2+ toxicities, including leukopenia. This treatment can be used safely in symptomatic patients without discontinuation of systemic therapy. Further larger prospective studies with longer follow-up are needed to confirm these results.

Citation Format: Chowdhary M, Sen N, Chowdhary A, Usha L, Cobleigh M, Patel KR, Wang D, Barry PN, Rao RD. Safety and efficacy of palbociclib and radiotherapy in metastatic breast cancer patients: Initial results of a novel combination [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 PD8-12.

Central Nervous System Metastasis in Patients with HER2-Positive Metastatic Breast Cancer: Patient Characteristics, Treatment, and Survival from SystHERs

PURPOSE

Patients with HER2-positive metastatic breast cancer (MBC) with central nervous system (CNS) metastasis have a poor prognosis. We report treatments and outcomes in patients with HER2-positive MBC and CNS metastasis from the Systemic Therapies for HER2-positive Metastatic Breast Cancer Study (SystHERs).

EXPERIMENTAL DESIGN

SystHERs (NCT01615068) was a prospective, U.S.-based, observational registry of patients with newly diagnosed HER2-positive MBC. Study endpoints included treatment patterns, clinical outcomes, and patient-reported outcomes (PRO).

RESULTS

Among 977 eligible patients enrolled (2012-2016), CNS metastasis was observed in 87 (8.9%) at initial MBC diagnosis and 212 (21.7%) after diagnosis, and was not observed in 678 (69.4%) patients. White and younger patients, and those with recurrent MBC and hormone receptor-negative disease, had higher risk of CNS metastasis. Patients with CNS metastasis at diagnosis received first-line lapatinib more commonly (23.0% vs. 2.5%), and trastuzumab less commonly (70.1% vs. 92.8%), than patients without CNS metastasis at diagnosis. Risk of death was higher with CNS metastasis observed at or after diagnosis [median overall survival (OS) 30.2 and 38.3 months from MBC diagnosis, respectively] versus no CNS metastasis [median OS not estimable: HR 2.86; 95% confidence interval (CI), 2.05-4.00 and HR 1.94; 95% CI, 1.52-2.49]. Patients with versus without CNS metastasis at diagnosis had lower quality of life at enrollment.

CONCLUSIONS

Despite advances in HER2-targeted treatments, patients with CNS metastasis continue to have a poor prognosis and impaired quality of life. Observation of CNS metastasis appears to influence HER2-targeted treatment choice.

Neratinib Efficacy and Circulating Tumor DNA Detection of HER2 Mutations in HER2 Nonamplified Metastatic Breast Cancer

Purpose: Based on promising preclinical data, we conducted a single-arm phase II trial to assess the clinical benefit rate (CBR) of neratinib, defined as complete/partial response (CR/PR) or stable disease (SD) ≥24 weeks, in HER2^mut nonamplified metastatic breast cancer (MBC). Secondary endpoints included progression-free survival (PFS), toxicity, and circulating tumor DNA (ctDNA) HER2^mut detection.Experimental Design: Tumor tissue positive for HER2^mut was required for eligibility. Neratinib was administered 240 mg daily with prophylactic loperamide. ctDNA sequencing was performed retrospectively for 54 patients (14 positive and 40 negative for tumor HER2^mut).Results: Nine of 381 tumors (2.4%) sequenced centrally harbored HER2^mut (lobular 7.8% vs. ductal 1.6%; P = 0.026). Thirteen additional HER2^mut cases were identified locally. Twenty-one of these 22 HER2^mut cases were estrogen receptor positive. Sixteen patients [median age 58 (31-74) years and three (2-10) prior metastatic regimens] received neratinib. The CBR was 31% [90% confidence interval (CI), 13%-55%], including one CR, one PR, and three SD ≥24 weeks. Median PFS was 16 (90% CI, 8-31) weeks. Diarrhea (grade 2, 44%; grade 3, 25%) was the most common adverse event. Baseline ctDNA sequencing identified the same HER2^mut in 11 of 14 tumor-positive cases (sensitivity, 79%; 90% CI, 53%-94%) and correctly assigned 32 of 32 informative negative cases (specificity, 100%; 90% CI, 91%-100%). In addition, ctDNA HER2^mut variant allele frequency decreased in nine of 11 paired samples at week 4, followed by an increase upon progression.Conclusions: Neratinib is active in HER2^mut, nonamplified MBC. ctDNA sequencing offers a noninvasive strategy to identify patients with HER2^mut cancers for clinical trial participation. Clin Cancer Res; 23(19); 5687-95. ©2017 AACR.

Abstract CT011: Circulating tumor DNA (ctDNA) sequencing for HER2 mutation (HER2mut) screening and response monitoring to neratinib in metastatic breast cancer (MBC)

Introduction: MutHER is a phase II trial that demonstrated the anti-tumor activity of the pan-HER inhibitor neratinib in HER2mut, non-amplified MBC. The major challenges to accrue to this trial were the large number of pts to screen for the 2-3% HER2mut population and the high rate (24%) of poor quality tumor DNA for sequencing. The goals of this ctDNA study were: 1) the concordance of HER2mut detected by ctDNA versus tumor testing; 2) the incidence of ctDNA HER2mut in HER2 non-amplified MBC; 3) changes in HER2mut variant allele frequency (VAF) on neratinib therapy.

Methods: A sample size of 30 negative (neg) controls was needed to ensure 90% confidence if ctDNA testing has &gt;90% specificity in detecting HER2mut. Thus, plasma from MBC pts obtained at screening for MutHER trial (Neg control: 40 pts without HER2mut on tumor testing; Positive (pos) control: 14 pts with known HER2mut who received neratinib) were subjected to Guardant360 ctDNA 70-gene panel sequencing (all exons of HER2 included). ctDNA from the 14 neratinib treated pts were also analyzed at week (wk) 4 and upon progression. ctDNA data from MBC pts clinically tested at Guardant Health were interrogated for HER2mut incidence.

Results: Among the 14 pts with tumor pos for HER2mut, ctDNA sequencing identified the same HER2mut in 11, discrepant HER2mut in 1, and neg in 2. The 2 pts with ctDNA neg for HER2mut had progressive disease (PD) and stable disease (SD &gt; 6 months) on neratinib, respectively. Among the 40 neg controls, 8 were not evaluable (no detectable ctDNA or assay unsuccessful) and all 32 successfully sequenced cases were neg for HER2mut. The sensitivity and specificity of ctDNA for HER2mut detection was 11/14 (79%, 90% CI: 53-94%) and 32/32 (100%, 90% CI: 91-100%), respectively. Among the 11 paired baseline and wk 4 samples, 9 (82%) had lower HER2mut VAFs at wk 4 than at baseline, with 1 complete response (CR), 1 partial response (PR), 5 SD, and 4 PD at wk 8 as best tumor response. Two pts had higher wk 4 ctDNA HER2mut VAFs and both had radiographic PD at wk 8. The absolute HER2mut VAF levels at wk 4 were significantly associated with TTP (Spearman rho=-0.69, p=0.02) and tumor size change (rho=0.67, p=0.05). The HER2mut VAFs were significantly higher at progression than wk 4 in all pts (p&lt;0.01). One pt acquired a new HER2mut T798I, which is analogous to the gate-keeper mutation EGFR T790M. The incidence of HER2mut without amplification in unselected consecutive MBC clinically tested by Guardant360 was 3% (48/1,584), with mutation pattern similar to published tumor testing data.

Conclusions: ctDNA sequencing is sensitive and highly specific in detecting HER2mut, offering a non-invasive method to identify pts for trials of HER2mut-targeted therapy. Decreased HER2mut VAFs at wk 4 was observed in 82% of cases, consistent with the on-target effect of neratinib. Increased HER2mut VAFs at wk 4 is a potential early marker of progression.

Citation Format: Cynthia Ma, Ron Bose, Feng Gao, Rachel Freedman, Melinda Telli, Gretchen Kimmick, Eric Winer, Michael Naughton, Matthew Goetz, Christy Russell, Debu Tripathy, Melody Cobleigh, Andres Forero, Timothy Pluard, Carey Anders, Shana Thomas, Jill Anderson, Caroline Bumb, Kimberly Banks, Richard Lanman, Richard Bryce, Alshad Lalani, John Pfeifer, Daniel Hays, Mark Pegram, Kimberly Blackwell, Philippe Bedard, Hussam Al-Kateb, Matthew Ellis. Circulating tumor DNA (ctDNA) sequencing for HER2 mutation (HER2mut) screening and response monitoring to neratinib in metastatic breast cancer (MBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT011. doi:10.1158/1538-7445.AM2017-CT011

Abstract P5-08-27: Treatment patterns and clinical outcomes in patients with hormone receptor (HR)+ HER2+ metastatic breast cancer and low vs high levels of HR positivity from the SystHERs Registry

Introduction In 2010, the cutoff for HR positivity in breast cancer was established as ≥1% of cells staining HR+, previously having varied from 1% to 10%. The impact of this change on treatment patterns and outcomes is poorly understood. SystHERs is a prospective, observational cohort registry of patients (pts) with HER2+ metastatic breast cancer (MBC) that commenced enrollment in 2012. To our knowledge, SystHERs is the largest registry to collect and analyze data for the HER2+ subgroup. We report baseline characteristics, treatment patterns, and early outcomes by %HR+ (1–9% vs 10–100%).

Methods SystHERs enrolled pts aged ≥18 years and within 6 months of HER2+ MBC diagnosis. For pts with locally-determined HR+ disease, defined as HR+ in primary or metastatic tissue, %HR+ is the highest percentage of ER+ or PR+ tissue in early breast cancer or MBC. The percentage of ER+ or PR+ cells was not reported for pts considered HR– by the investigator. Median overall survival (OS; Kaplan–Meier) and hazard ratios (Cox regression) were estimated.

Results As of Feb 1, 2016, data were available for 872 eligible pts with known HR status, of whom 608 (70%) had HR+ disease. Of the 608 pts, 53 (9%) had 1–9%HR+ and 496 (82%) had 10–100%HR+; %HR+ was not reported for 59 pts. Baseline characteristics were similar between %HR+ subgroups (Table 1).

As shown in Table 2, the 1–9%HR+ subgroup was less likely to receive first-line hormonal therapy (26%) than the 10–100%HR+ subgroup (56%). 87% and 79% of pts received chemotherapy, respectively.

Median time from MBC diagnosis was 16.5 months (range, 0.4–49.4 months). Median OS was not reached at the data cutoff. The number of deaths was 13 (25%) in the 1–9%HR+ subgroup, and 68 (14%) in the 10–100%HR+ subgroup (log-rank P=0.025). The OS hazard ratio (0.514, 95% CI 0.283–0.931) favored the 10–100%HR+ subgroup. OS did not differ significantly between pts with 1–9%HR+ vs HR– disease (log-rank P=0.582, hazard ratio 1.185, 95% CI 0.647–2.169).

Table 1. Baseline characteristics 1-9%HR+ (n=53)10-100%HR+ (n=496)HR– (n=264)Age at MBC diagnosis, median yrs (range)54 (30–86)57 (21–86)55 (28–88)Race, %   White838372Black151320Premenopausal, %282522ECOG performance status, %   04654441463942≥2878MBC diagnosis type, %   De novo404958Recurrent605142Visceral, %*686275*Non-hepatic abdominal, ascites, CNS, liver, lung, or pleural effusion sites of metastasis

Table 2. First-line treatment 1-9%HR+ (n=53)10-100%HR+ (n=496)HR– (n=264)HER2-targeted therapy, %969391Chemotherapy, %877989Hormonal therapy, %26564

Conclusions These preliminary observational data suggest potential differences in treatment patterns and survival outcomes in low vs moderate/high HR+ expressers, with the former being less likely to receive hormonal therapy (26% vs 56%). Furthermore, low HR positivity was associated with poorer OS and was similar to OS observed in pts with HR– disease.

Citation Format: Jahanzeb M, Tripathy D, Rugo H, Swain S, Kaufman PA, Mayer M, Hurvitz S, O'Shaughnessy J, Mason G, Yardley DA, Brufsky A, Chu L, Antao V, Beattie M, Yoo B, Cobleigh M. Treatment patterns and clinical outcomes in patients with hormone receptor (HR)+ HER2+ metastatic breast cancer and low vs high levels of HR positivity from the SystHERs Registry [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 P5-08-27.

Marker Panel Predictive of Lymph Node Metastasis in Young Patients with Breast Carcinoma

Breast cancer is being diagnosed more frequently in young women. It is important to identify tumors with greater metastatic potential since this information will provide a basis for noninvasive staging of the axilla. The studied population consisted of 66 patients with infiltrating breast carcinoma (56 ductal, 10 lobular) aged 20-34 (mean 29) years. Lymph node status was correlated with the following parameters: size, grade, p53 expression, MIB-1, CD44, c-Erb-2, estrogen, progesterone receptors, and a family history of breast cancer. Immunohistochemical studies utilizing avidinbiotin-peroxidase complex method were performed on formalin-fixed, paraffinembedded tissue. Thirty-nine patients (59%) had positive lymph nodes and 27 (41%) had negative lymph nodes. In multivariate logistic regression analysis, two models with size (p=.0002) and p53 (p=.0379) or size (p=.0002) and MIB-1 (p=.0462) were predictive of nodal involvement. For TI lesions, p53 positivity increased the probability of nodal involvement from 18% to 46% and, for T2 lesions, from 65% to 89%. In the second model, for TI lesions MIB-1 positivity increased the probability of nodal involvement from 10% to 36% and, for T2 lesions, from 48% to 82%. Size, p53, and MIB-1 were found to be valid independent predictors of lymph node metastasis in TI and T2 breast carcinomas in young women. The combination of size with p53 or MIB-1 increases dramatically the predictive impact of these parameters on nodal status. These data may prove useful in selecting patients with increased risk of dissemination and provide a basis for staging the axilla noninvasively.

Progression-free survival as surrogate end point for overall survival in clinical trials of HER2-targeted agents in HER2-positive metastatic breast cancer

BACKGROUND

The gold standard end point in randomized clinical trials in metastatic breast cancer (MBC) is overall survival (OS). Although therapeutics have been approved based on progression-free survival (PFS), its use as a primary end point is controversial. We aimed to assess to what extent PFS may be used as a surrogate for OS in randomized trials of anti-HER2 agents in HER2+ MBC.

METHODS

Eligible trials accrued HER2+ MBC patients in 1992-2008. A correlation approach was used: at the individual level, to estimate the association between investigator-assessed PFS and OS using a bivariate model and at the trial level, to estimate the association between treatment effects on PFS and OS. Correlation values close to 1.0 would indicate strong surrogacy.

RESULTS

We identified 2545 eligible patients in 13 randomized trials testing trastuzumab or lapatinib. We collected individual patient data from 1963 patients and retained 1839 patients from 9 trials for analysis (7 first-line trials). During follow-up, 1072 deaths and 1462 progression or deaths occurred. The median survival time was 22 months [95% confidence interval (CI) 21-23 months] and the median PFS was 5.7 months (95% CI 5.5-6.1 months). At the individual level, the Spearman correlation was equal to ρ = 0.67 (95% CI 0.66-0.67) corresponding to a squared correlation value of 0.45. At the trial level, the squared correlation between treatment effects (log hazard ratios) on PFS and OS was provided by R(2) = 0.51 (95% CI 0.22-0.81).

CONCLUSIONS

In trials of HER2-targeted agents in HER2+ MBC, PFS moderately correlates with OS at the individual level and treatment effects on PFS correlate moderately with those on overall mortality, providing only modest support for considering PFS as a surrogate. PFS does not completely substitute for OS in this setting.

Abstract P5-05-07: Elucidating molecular resistance to trastuzumab using next generation sequencing in isogenic cell models

A minority of all breast cancers will express increased levels of the ERBB2 protein. They are eligible for trastuzumab-based therapy. Some will respond, but all will progress. Thus, the problem of resistance to trastuzumab has generated an urgent need to determine the underlying mechanisms of that resistance.

Cancer is a genetic disease and the mechanism of trastuzumab resistance is likely also genetic in nature. However, the significant genomic heterogeneity between and within patient tumors greatly complicates the identification of a genetic mechanism of resistance for trastuzumab. In order to overcome some of these challenges, we looked to an isogenic model of trastuzumab resistance. We acquired the trastuzumab-sensitive breast cancer cell line, BT474 and two clones of this cell line that were conditioned to exhibit trastuzumab resistance.

To investigate a possible genetic mechanism of trastuzumab-resistance, we performed whole exome sequencing using Ampliseq chemistry on the Ion Torrent platform from Life Technologies and paired-end RNA-sequencing on the Illumina HiSeq platform. Next-generation sequencing data was bioinformatically analyzed using tools that allowed us to filter relevant variants based on statistical and functional significance. Variants of interest were those that that arose during drug treatment, which were identified as those in each of the resistant clones, which were novel compared to the parent clone. Proteins from whole cell lysates were resolved in two dimensions using 3-10 nonlinear strips for isoelectric focusing followed by resolution via 4-20% SDS-PAGE. Proteins were visualized via Gelcode blue and cored with a biopsy punch, trypsinized, and submitted for protein ID on an LTQ XL mass spectrometer. We performed functional validation of genetic alterations through the use of somatic cell gene targeting of an ERBB2-expressing clone of the MCF-10A cell lines, a non-tumorigenic model of breast cancer, which is sensitive to trastuzumab.

Exome sequencing initially yielded more than 10,000 unique DNA variants across the three clones, which after bioinformatic analysis resulted in ∼1000 variants of interest. Two-dimensional gel electrophoresis revealed 25-30 differentially expressed proteins per sample. Correlation between the sequencing and proteomics data provided us with a candidate gene list of less than 100 genes and several cellular pathways related to growth signaling and immunity. Genetic alterations were tested for their ability to cause trastuzumab resistance in MCF-10A clones.

We describe herein a detailed molecular analysis for a model of trastuzumab resistance. Validated genetic alterations will be investigated in a unique collection of archival specimens, which we hope will open the path towards the development of novel agents to augment the effects of trastuzumab.

Citation Format: Abde M Abukhdeir, Matthew Najor, Sanja Turturro, Melissa R Pergande, Jeffrey A Borgia, Hanif G Khalak, Melody Cobleigh. Elucidating molecular resistance to trastuzumab using next generation sequencing in isogenic cell models [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 P5-05-07.

Abstract P3-07-14: Increasing proportion of de novo compared with recurrent HER2-positive metastatic breast cancer: Early results from the systemic therapies for HER2-positive metastatic breast cancer registry study

Introduction

The Systemic Therapies for HER2-Positive Metastatic Breast Cancer Registry (SystHERs) is a US-based prospective observational cohort study currently enrolling patients with HER2-positive metastatic breast cancer (MBC). It began in 2012 and aims to provide real-world insight into the disease course, treatment patterns and associated clinical outcomes, and patient-reported experiences of disease. Here we describe the baseline characteristics of this population to date, including the proportion of patients with de novo and recurrent HER2-positive MBC.

Methods

SystHERs aims to enroll ∼1000 patients with HER2-positive MBC within 6 months of first metastatic diagnosis. At enrollment, investigators report whether patients have recurrent or de novo MBC, the latter defined as distant metastases at the time of initial MBC diagnosis.

Results

As of February 17, 2014, data are available from 306 of 319 enrolled patients. Forty-six percent (142/306) had de novo HER2-positive MBC. For the 54% (164/306) with recurrent HER2-positive MBC, median disease-free interval (DFI, defined here as time from early-stage breast cancer diagnosis to diagnosis of MBC) was 43.6 (range 0.5–270.2) months. For these patients with recurrent disease, 54% (89/164) received (neo)adjuvant HER2-targeted therapy. Baseline patient and tumor characteristics are shown below.

CharacteristicOverall (n=306)De novo (n=142)Recurrent (n=164)Age, median (range)57 (27-86)54 (27-83)59 (30-86)Race, n (%)White233 (76)105 (74)128 (78)Black54 (18)28 (20)26 (16)Other8 (3)3 (2)5 (3)Not available11 (4)6 (4)5 (3)Ethnicity, n(%)Not Hispanic257 (84)120 (85)137 (84)Hispanic31 (10)17 (12)14 (9)Not available18 (6)5 (4)13 (8)Pre-menopausal, n (%)61 (20)42 (30)19 (12)Hormone receptor status, n (%)ER and/or PR positive209 (68)90 (63)119 (73)ER and PR negative92 (30)50 (35)42 (26)Unknown5 (2)2 (1)3 (2)Median number of metastatic sites, (range)2.0 (1-7)2.0 (1-6)2.0 (1-7)Sites of metastasis, n (%)Bone141 (46)76 (54)65 (40)Liver120 (39)63 (44)57 (35)Nodes89 (29)49 (35)40 (24)Lung87 (28)38 (27)49 (30)Chest wall43 (14)12 (9)31 (19)CNS30 (10)9 (6)21 (13)

Conclusions

The proportion of patients with de novo MBC appears to have increased over time to 46% in SystHERs, compared with 33% in RegistHER, a registry study that enrolled 1023 patients with HER2-positive MBC from 2003–2006 (Yardley et al, 2014), and predated the broad use of HER2-targeted therapy in the (neo)adjuvant setting. The DFI for patients with recurrent HER2-positive MBC also appears to be longer (median DFI 43.6 months in SystHERs vs. 32.6 months in registHER). We hypothesize that the proportion of patients with de novo MBC within the metastatic population is higher due to the use of advanced screening techniques which allow better detection of metastases, and due to a reduction in recurrences related to the availability of HER2-targeted adjuvant therapy. Changes in the population characteristics of patients with HER2-positive MBC may impact treatment strategies and have trial design implications. Updated data from approximately 500 patients are expected by the time of presentation.

Citation Format: Debu Tripathy, Adam Brufsky, Melody Cobleigh, Mohammad Jahanzeb, Peter Kaufman, Ginny Mason, Musa Mayer, Joyce O'Shaughnessy, Hope Rugo, Sandra M Swain, Denise A Yardley, Mary Beattie, Bongin Yoo, Sara Hurvitz. Increasing proportion of de novo compared with recurrent HER2-positive metastatic breast cancer: Early results from the systemic therapies for HER2-positive metastatic breast cancer registry study [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 P3-07-14.

Genetic variant predicts bevacizumab-induced hypertension in ECOG-5103 and ECOG-2100

BACKGROUND

Bevacizumab has broad anti-tumour activity, but substantial risk of hypertension. No reliable markers are available for predicting bevacizumab-induced hypertension.

METHODS

A genome-wide association study (GWAS) was performed in the phase III bevacizumab-based adjuvant breast cancer trial, ECOG-5103, to evaluate for an association between genotypes and hypertension. GWAS was conducted in those who had experienced systolic blood pressure (SBP) >160 mm Hg during therapy using binary analysis and a cumulative dose model for the total exposure of bevacizumab. Common toxicity criteria (CTC) grade 3-5 hypertension was also assessed. Candidate SNP validation was performed in the randomised phase III trial, ECOG-2100.

RESULTS

When using the phenotype of SBP>160 mm Hg, the most significant association in SV2C (rs6453204) approached and met genome-wide significance in the binary model (P=6.0 × 10(-8); OR=3.3) and in the cumulative dose model (P=4.7 × 10(-8); HR=2.2), respectively. Similar associations with rs6453204 were seen for CTC grade 3-5 hypertension but did not meet genome-wide significance. Validation study from ECOG-2100 demonstrated a statistically significant association between this SNP and grade 3/4 hypertension using the binary model (P-value=0.037; OR=2.4).

CONCLUSIONS

A genetic variant in SV2C predicted clinically relevant bevacizumab-induced hypertension in two independent, randomised phase III trials.

Population pharmacokinetics of trastuzumab emtansine (T-DM1), a HER2-targeted antibody-drug conjugate, in patients with HER2-positive metastatic breast cancer: clinical implications of the effect of covariates

Purpose

Trastuzumab emtansine (T-DM1) is an antibody–drug conjugate comprising the humanized monoclonal antibody trastuzumab linked to DM1, a highly potent cytotoxic agent. A population pharmacokinetic (PK) analysis was performed to estimate typical values and interindividual variability of T-DM1 PK parameters and the effects of clinically relevant covariates.

Methods

Serum samples were collected from 671 patients with human epidermal growth factor receptor 2-positive locally advanced or metastatic breast cancer (MBC) who received single-agent T-DM1 in five phase I to phase III studies. Nonlinear mixed-effects modeling with the first-order conditional estimation method was used.

Results

A linear two-compartment model with first-order elimination from the central compartment described T-DM1 PKs in the clinical dose range. T-DM1 elimination clearance was 0.676 L/day, volume of distribution in the central compartment (V_c) was 3.127 L, and terminal elimination half-life was 3.94 days. Age, race, region, and renal function did not influence T-DM1 PK. Given the low-to-moderate effect of all statistically significant covariates on T-DM1 exposure, none of these covariates is expected to result in a clinically meaningful change in T-DM1 exposure.

Conclusions

T-DM1 PK properties are consistent and predictable in patients. A further refinement of dose based on baseline covariates other than body weight for the current 3.6 mg/kg regimen would not yield clinically meaningful reductions in interindividual PK variability in patients with MBC.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-014-2500-2) contains supplementary material, which is available to authorized users.

Abstract P5-18-24: Population pharmacokinetics of trastuzumab emtansine, a HER2-targeted antibody-drug conjugate, in patients with HER2-positive metastatic breast cancer: clinical implications of the effect of various covariates

Background: Trastuzumab emtansine (T-DM1) is a HER2-targeted antibody-drug conjugate composed of the humanized monoclonal antibody trastuzumab, the potent cytotoxic agent DM1 (a microtubule inhibitor), and a stable thioether linker. To estimate typical pharmacokinetic (PK) parameter values and interpatient variability, a population PK model for T-DM1 was previously developed from 1 phase 1 (0.3 to 4.8 mg/kg in qw or q3w regimens) and 2 phase 2 (3.6 mg/kg q3w) trials (Gupta, J Clin Pharmacol 2012). The model reported here has been updated with additional data from 2 randomized trials (phase 2 TDM4450g and phase 3 EMILIA, 3.6 mg/kg q3w). Another phase 2 trial (TDM4688g) was used for external validation of the model. The effect of demographic and pathophysiological covariates on the PK of T-DM1 was explored to better understand the clinical factors that might affect exposure and clinical outcome for individual patients.

Methods: For the current analysis, 9934 T-DM1 serum concentration-time data points from 671 patients were simultaneously fitted using NONMEM® software. T-DM1 concentration-time data to date are best described using a 2-compartment linear model. All relevant and plausible covariates likely to have an effect on T-DM1 systemic exposure, or likely to have clinical relevance, were explored for possible correlation with the key T-DM1 PK parameters of clearance (CL) and central volume of distribution (Vc). These covariates include those related to demographics, renal and hepatic function, disease status, and treatment history.

Results: The estimated CL for T-DM1 is 0.68 L/day, Vc is 3.13 L, and the terminal half-life is 3.94 days. Interindividual variability (IIV) of the base model is 25.6% and 17.5% for CL and Vc, respectively. Patients with greater body weight, sum of longest dimension of target lesions, serum concentration of shed HER2 extracellular domain, and aspartate aminotransferase concentrations, as well as patients with lower serum albumin and baseline trastuzumab concentrations, have statistically faster CL. Patients with greater body weight also have statistically larger Vc. Incorporation of these covariates (P&lt;0.001 by likelihood ratio test) decreased IIV of CL and Vc to 19.1% and 11.7%, respectively. All covariates together explain 44.4% and 55.8% of IIV in CL and Vc, respectively. The model sensitivity analysis suggests that a patient with a statistically significant PK covariate value at the 5th or 95th percentile of the population will have a &lt;20% difference in cumulative exposure (as represented by area under the T-DM1 concentration-time curve) compared with a typical patient with a median covariate value.

Conclusions: A relatively small IIV for the estimated T-DM1 PK parameters of CL and Vc was observed. None of the evaluated covariates had a clinically meaningful magnitude of effect on T-DM1 exposure (&lt;20% difference for patients with 5th and 95th percentiles vs patients with median value of covariates) that would justify a further dose adjustment. The body weight–based dose of 3.6 mg/kg q3w without further correction for other factors is considered appropriate in ongoing clinical trials.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-18-24.

Pathologic findings in MRI-guided needle core biopsies of the breast in patients with newly diagnosed breast cancer

The role of MRI in the management of breast carcinoma is rapidly evolving from its initial use for specific indications only to a more widespread use on all women with newly diagnosed early stage breast cancer. However, there are many concerns that such widespread use is premature since detailed correlation of MRI findings with the underlying histopathology of the breast lesions is still evolving and clear evidence for improvements in management and overall prognosis of breast cancer patients evaluated by breast MRI after their initial cancer diagnosis is lacking. In this paper, we would like to bring attention to a benign lesion that is frequently present on MRI-guided breast biopsies performed on suspicious MRI findings in the affected breast of patients with a new diagnosis of breast carcinoma.

Association of vascular endothelial growth factor and vascular endothelial growth factor receptor-2 genetic polymorphisms with outcome in a trial of paclitaxel compared with paclitaxel plus bevacizumab in advanced breast cancer: ECOG 2100

PURPOSE

No biomarkers have been identified to predict outcome with the use of an antiangiogenesis agent for cancer. Vascular endothelial growth factor (VEGF) genetic variability has been associated with altered risk of breast cancer and variable promoter activity. Therefore, we evaluated the association of VEGF genotype with efficacy and toxicity in E2100, a phase III study comparing paclitaxel versus paclitaxel plus bevacizumab as initial chemotherapy for metastatic breast cancer.

PATIENTS AND METHODS

DNA was extracted from tumor blocks of patients from E2100. Three hundred sixty-three samples were available to evaluate associations between genotype and outcome. Genotyping was performed for selected polymorphisms in VEGF and VEGF receptor 2. Testing for associations between each polymorphism and efficacy and toxicity was performed.

RESULTS

The VEGF-2578 AA genotype was associated with a superior median overall survival (OS) in the combination arm when compared with the alternate genotypes combined (hazard ratio = 0.58; 95% CI, 0.36 to 0.93; P = .023). The VEGF-1154 A allele also demonstrated a superior median OS with an additive effect of each active allele in the combination arm but not the control arm (hazard ratio = 0.62; 95% CI, 0.46 to 0.83; P = .001). Two additional genotypes, VEGF-634 CC and VEGF-1498 TT, were associated with significantly less grade 3 or 4 hypertension in the combination arm when compared with the alternate genotypes combined (P = .005 and P = .022, respectively).

CONCLUSION

Our data support an association between VEGF genotype and median OS as well as grade 3 or 4 hypertension when using bevacizumab in metastatic breast cancer.

Paclitaxel plus bevacizumab versus paclitaxel alone for metastatic breast cancer

BACKGROUND

In an open-label, randomized, phase 3 trial, we compared the efficacy and safety of paclitaxel with that of paclitaxel plus bevacizumab, a monoclonal antibody against vascular endothelial growth factor, as initial treatment for metastatic breast cancer.

METHODS

We randomly assigned patients to receive 90 mg of paclitaxel per square meter of body-surface area on days 1, 8, and 15 every 4 weeks, either alone or with 10 mg of bevacizumab per kilogram of body weight on days 1 and 15. The primary end point was progression-free survival; overall survival was a secondary end point.

RESULTS

From December 2001 through May 2004, a total of 722 patients were enrolled. Paclitaxel plus bevacizumab significantly prolonged progression-free survival as compared with paclitaxel alone (median, 11.8 vs. 5.9 months; hazard ratio for progression, 0.60; P<0.001) and increased the objective response rate (36.9% vs. 21.2%, P<0.001). The overall survival rate, however, was similar in the two groups (median, 26.7 vs. 25.2 months; hazard ratio, 0.88; P=0.16). Grade 3 or 4 hypertension (14.8% vs. 0.0%, P<0.001), proteinuria (3.6% vs. 0.0%, P<0.001), headache (2.2% vs. 0.0%, P=0.008), and cerebrovascular ischemia (1.9% vs. 0.0%, P=0.02) were more frequent in patients receiving paclitaxel plus bevacizumab. Infection was more common in patients receiving paclitaxel plus bevacizumab (9.3% vs. 2.9%, P<0.001), but febrile neutropenia was uncommon (<1% overall).

CONCLUSIONS

Initial therapy of metastatic breast cancer with paclitaxel plus bevacizumab prolongs progression-free survival, but not overall survival, as compared with paclitaxel alone. (ClinicalTrials.gov number, NCT00028990 [ClinicalTrials.gov].).

The basal subtype of breast carcinomas may represent the group of breast tumors that could benefit from EGFR-targeted therapies

The recent understanding of the molecular basis of breast cancer growth and progression led to the identification of tumor subtypes with potentially different biologic behavior. In addition, targeted therapies are increasingly successful in cancer treatment. We recently reported that most of the ER-negative/PR-negative/HER2-negative patients, a group that presents a therapeutic challenge for the oncologist, express EGFR. We now report that the majority of these patients express cytokeratin CK5/6 and therefore belong to the basal subtype of breast carcinomas. These basal subtype lesions are usually high-grade tumors of ductal histology with a high proliferation rate. We propose that the majority of the "triple negative" patients have basal subtype tumors with high EGFR expression and that these tumors may be the subgroup of breast carcinomas that could potentially benefit the most from novel EGFR-targeted therapeutic strategies.

The challenging estrogen receptor-negative/ progesterone receptor-negative/HER-2-negative patient: a promising candidate for epidermal growth factor receptor-targeted therapy?

While epidermal growth factor receptor (EGFR)-targeted therapy has been very promising in a number of human malignancies, to date these targeted biologic agents have not proven effective in breast cancer. However, the EGFR tyrosinase inhibitors have been used indiscriminately against all types of breast tumors, perhaps missing a subpopulation of patients who may be prime candidates for EGFR-targeted therapy. In this communication we propose that patients with estrogen receptor (ER)-negative/progesterone receptor (PR)-negative/HER-2-negative tumors, which currently present a therapeutic challenge for the oncologist, may be the subgroup of breast cancer patients that might benefit from specific EGFR-targeted therapies.

Randomized phase III study of trastuzumab, paclitaxel, and carboplatin compared with trastuzumab and paclitaxel in women with HER-2-overexpressing metastatic breast cancer

PURPOSE

This randomized, multicenter, phase III trial evaluated the efficacy and safety of trastuzumab and paclitaxel with or without carboplatin as first-line therapy for women with HER-2-overexpressing metastatic breast cancer (MBC).

PATIENTS AND METHODS

HER-2 overexpression was defined as immunohistochemical staining scores of 2+ or 3+. Between November 1998 and May 2002, 196 women with HER-2-overexpressing MBC were randomly assigned to six cycles of either trastuzumab 4 mg/kg loading dose plus 2 mg/kg weekly thereafter with paclitaxel 175 mg/m2 every 3 weeks (TP), or trastuzumab 4 mg/kg loading dose plus 2 mg/kg weekly thereafter with paclitaxel 175 mg/m2 and carboplatin area under the time-concentration curve = 6 every 3 weeks (TPC) followed by weekly trastuzumab alone.

RESULTS

Baseline characteristics of the 196 patients were well balanced between study arms. Objective response rate (ORR) was 52% (95% CI, 42% to 62%) for TPC versus 36% (95% CI, 26% to 46%) for TP (P = .04). Median progression-free survival (PFS) was 10.7 months for TPC and 7.1 months for TP (hazard ratio [HR], 0.66; 95% CI, 0.59 to 0.73; P = .03). Improved clinical outcomes with TPC were most evident in HER-2 3+ patients, with an ORR of 57% (95% CI, 45% to 70%) v 36% (95% CI, 25% to 48%; P = .03) and median PFS of 13.8 v 7.6 months (P = .005) for TPC and TP, respectively (HR, 0.55; 95% CI, 0.46 to 0.64). Both regimens were well tolerated, and febrile neutropenia and neurotoxicity occurred infrequently; grade 4 neutropenia occurred more frequently with TPC (P < .01).

CONCLUSION

The addition of carboplatin to paclitaxel and trastuzumab improved ORR and PFS in women with HER-2-overexpressing MBC. This well-tolerated regimen represents a new therapeutic option.

Genetic testing in an ethnically diverse cohort of high-risk women: a comparative analysis of BRCA1 and BRCA2 mutations in American families of European and African ancestry

CONTEXT

Ten years after BRCA1 and BRCA2 were first identified as major breast cancer susceptibility genes, the spectrum of mutations and modifiers of risk among many ethnic minorities remain undefined.

OBJECTIVES

To characterize the clinical predictors, spectrum, and frequency of BRCA1 and BRCA2 mutations in an ethnically diverse high-risk clinic population and to evaluate the performance of the BRCAPRO statistical model in predicting the likelihood of a mutation.

DESIGN, SETTING, AND PARTICIPANTS

Comparative analysis of families (white, Ashkenazi Jewish, African American, Hispanic, Asian) with 2 or more cases of breast and/or ovarian cancer among first- and second-degree relatives. Families were identified at US sites between February 1992 and May 2003; in each family, the individual with the highest probability of being a mutation carrier was tested.

MAIN OUTCOME MEASURES

Frequency of BRCA1 and BRCA2 mutations and area under the receiver operating characteristic curve for the BRCAPRO model.

RESULTS

The mutation spectrum was vastly different between families of African and European ancestry. Compared with non-Hispanic, non-Jewish whites, African Americans had a lower rate of deleterious BRCA1 and BRCA2 mutations but a higher rate of sequence variations (27.9% vs 46.2% and 44.2% vs 11.5%; P<.001 for overall comparison). Deleterious mutations in BRCA1 and BRCA2 were highest for Ashkenazi Jewish families (69.0%). Early age at diagnosis of breast cancer and number of first- and second-degree relatives with breast and ovarian cancer were significantly associated with an increased likelihood of carrying a BRCA1 or BRCA2 mutation. In discriminating between mutation carriers, BRCAPRO performed as well in African American families as it did in white and Jewish families, with an area under the curve of 0.77 (95% confidence interval, 0.61-0.88) for African American families and 0.70 (95% confidence interval, 0.60-0.79) for white and Jewish families combined.

CONCLUSIONS

These data support the use of BRCAPRO and genetic testing for BRCA1 and BRCA2 mutations in the management of high-risk African American families. Irrespective of ancestry, early age at diagnosis and a family history of breast and ovarian cancer are the most powerful predictors of mutation status and should be used to guide clinical decision making.

Safety of Treatment of Metastatic Breast Cancer With Trastuzumab Beyond Disease Progression

Purpose

In a pivotal phase III trial, the addition of trastuzumab to chemotherapy significantly improved response rate, time to disease progression, and overall survival in women with HER2 overexpressing metastatic breast cancer. We conducted an extension study to this trial to obtain additional safety information and to provide trastuzumab following disease progression.

Patients and Methods

A total of 247 patients with documented disease progression received weekly intravenous trastuzumab in the extension study. Concurrent therapies were administered at the discretion of the treating physician. Patient groups were based on initial study treatment: chemotherapy alone (group 1, n = 154) or chemotherapy plus trastuzumab (group 2, n = 93).

Results

Sixty-eight percent of group 1 and 76% of group 2 received chemotherapy plus trastuzumab in the extension trial; the remainder received trastuzumab alone or combined with palliative radiotherapy or hormonal therapy. Seventy-six percent of group 1 and 55% of group 2 experienced at least one adverse event, similar to effects observed in the pivotal trial. Symptomatic or asymptomatic cardiac dysfunction occurred in 9% of group 1 and 2% of group 2 patients. Overall objective response rates were 14% in group 1 and 11% in group 2; median durations of response exceeded 6 months in both groups.

Conclusion

Our results suggest that prolonged use of trastuzumab therapy is safe and well tolerated. Longer durations of therapy did not appear to increase the risk of cardiac dysfunction. Patients progressing on trastuzumab-containing therapy demonstrate some response to a second trastuzumab-containing regimen. The independent contribution of trastuzumab in this setting merits further study.

Predictors of lymph node metastasis in T1 breast carcinoma, stratified by patient age

It is important to identify T1-substage breast carcinomas (BCs) which are inherently aggressive, so that these can be managed more assertively. The purpose of this study was to distinguish those T1 BCs with the potential to metastasize to axillary lymph nodes from those lacking that ability by multiparametric analysis of several clinicopathologic features. The authors studied 197 patients with invasive BC who had undergone modified radical mastectomy; 161 tumors were ductal and 26 were lobular BCs. The study group was stratified by age into two groups: </=34 years (n = 34) and 35-84 years (n = 153). Pathologic lymph node status was correlated with estrogen receptor (ER) and progesterone receptor (PR) tumor positivity, MIB-1 proliferation index, and immunoreactivity for mutant p53 protein. These factors were studied immunohistologically using standard methodology and microwave-mediated epitope retrieval. Statistical analyses employed accepted techniques. Women in this study ranged from 22 to 84 years of age; 39 (21%) had positive lymph nodes. ER-positive tumors comprised 73% of the total; similarly, 65% were PR positive. The MIB-1 index was greater than 10% in 44% of lesions, and 14% demonstrated labeling for mutant p53 protein. Using crude odds ratio data, the MIB-1 index was the only indicator found to predict lymph node metastasis significantly (p < 0.001). Moreover, even when adjustments were made for patient age, logistic regression analysis confirmed the utility of MIB-1-values of greater than 10% in this context, with a 4.4 greater likelihood of metastasis (p < 0.001). MIB-1 indices of greater than 10% are associated with a risk of lymph node metastasis from T1 BCs, independent of patient age. Hormone receptor status and immunohistologic p53 status are not predictors of nodal involvement in this specific setting.

A randomized phase II pilot trial of adjuvant marimastat in patients with early-stage breast cancer

BACKGROUND

This pilot trial was performed to evaluate the safety, toxicity and pharmacokinetics of chronic therapy with the matrix metalloproteinase inhibitor marimastat in the adjuvant treatment of breast cancer.

PATIENTS AND METHODS

Patients with high-risk node negative or node positive breast cancer received marimastat either 5 or 10 mg p.o. b.i.d. for 12 months. Marimastat was given either as a single agent following completion of adjuvant chemotherapy or concurrently with tamoxifen.

RESULTS

Sixty-three patients were enrolled from June 1997 to May 1998. All patients have completed 12 months of treatment or have discontinued therapy due to toxicity, relapse or intercurrent illness. Moderate (WHO criteria) arthralgia/arthritis was reported by 34% of patients receiving 5 mg b.i.d. and 45% of patients receiving 10 mg b.i.d.; severe arthralgia/arthritis was reported by 6% and 23% of patients, respectively. Six patients (19%) receiving 5 mg b.i.d. and 11 (35%) receiving 10 mg b.i.d. discontinued marimastat therapy due to toxicity. Trough plasma levels were rarely within the target range for biological activity (40-200 ng/ml) with mean concentration for patients receiving: 5 mg b.i.d. = 7.5; 5 mg b.i.d. plus tamoxifen = 6.9; 10 mg b.i.d. = 11.9; 10 mg b.i.d. plus tamoxifen = 12.8.

CONCLUSIONS

A randomized adjuvant trial with marimastat is not warranted as chronic administration cannot maintain plasma levels with the target range.