Abstract OT1-02-03: TBCRC 044: A randomized phase II study of pembrolizumab in combination with carboplatin versus carboplatin alone in breast cancer patients with chest wall disease

Background: Patients with breast cancer (BC) and chest wall disease have limited treatment options. We hypothesize that checkpoint inhibition may be an effective treatment approach due to the inflammatory nature of chest wall infiltration, and the association of PD-1 expression with lymphocytic infiltration. Platinum chemotherapy may facilitate anti-tumor immunity in a synergistic manner, and clinical studies of the PD-1 inhibitor pembrolizumab with platinum combinations have been effective in the treatment of advanced lung cancer. In this study, we will evaluate the combination of carboplatin and pembrolizumab in BC patients with chest wall disease.

Methods: This is a randomized phase II multicenter study in the TBCRC including patients with advanced, unresectable BC with hormone resistant or triple negative chest wall disease. Patients may have had prior surgery, prior chest wall radiation is not required, and other sites of distant metastases are allowed. Eighty-four patients at TBCRC sites will be randomized 2:1 to receive pembrolizumab and carboplatin (n=56, Arm A) or carboplatin alone (n=28, Arm B) until disease progression. Patients randomized to Arm B may cross-over following progression to pembrolizumab alone (Arm Bx). Patients in Arm A will be treated with pembrolizumab 200 mg IV and carboplatin AUC 5 IV every 3 weeks for at least 6 cycles followed by maintenance pembrolizumab 200 mg IV every 3 weeks if stable or responding disease. Patients in Arm B will be treated with carboplatin AUC 5 IV every 3 weeks until progression, then may cross-over to pembrolizumab 200 mg IV every 3 weeks alone (Arm Bx). An interim analysis for futility will be performed after 18 patients are enrolled into Arm B to allow early closure of that arm for lack of efficacy. The primary endpoint is disease control rate at 18 weeks of treatment; the study is powered to detect a 20% difference in disease control rates between arms (hazard ratio 0.52, α= 0.10, β= 0.20). Secondary endpoints include progression free survival, toxicity, and response based on PD-L1 expression and irRECIST. Exploratory endpoints include association of response with a number of biomarkers including tumor PD-L1 gene expression, tumor and peripheral blood immune composition and cytokine expression, peripheral T-cell PD-1 expression, circulating tumor DNA, circulating tumor cells, and tumor MYC genomic expression using tumor biopsy and peripheral blood testing before and after treatment. This study should be open to accrual by August of 2017. (NCT03095352)

Citation Format: Vidula N, Goga A, Krummel M, Hwang J, Liu M, Park BH, Nanda R, Pohlmann P, Storniolo AM, Van Poznak C, Brufsky A, Abramson V, Wolff A, Rugo HS. TBCRC 044: A randomized phase II study of pembrolizumab in combination with carboplatin versus carboplatin alone in breast cancer patients with chest wall disease [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT1-02-03.

Abstract P2-02-12: Cell free DNA analysis identifies actionable ERBB2 amplifications in patients with HER2 negative breast cancer

Identification of ERBB2 (HER2) overexpression in metastatic breast cancer informs utilization of HER2 targeted therapy. The NCCN recommends HER2 expression re-evaluation at the first disease recurrence in patients with negative or equivocal tissue status given results discrepancies due to inadequate tissue biopsy, tumoral heterogeneity, biopsy technique or fixation as well as discordance in ERBB2 (HER2) expression between primary and metastatic lesions. We examined the incidence of ERBB2 (HER2) negative to positive “flips” (e.g. to ERBB2-amplified in plasma) in a cohort of patients who underwent a blood-based cell-free DNA (cfDNA) assay at a CLIA-certified/CAP-accredited/NYSDOH-approved molecular diagnostic laboratory.

Laboratory database was queried for samples from patients with a breast cancer diagnosis. The query was filtered to ensure patients with multiple cfDNA timepoints were counted only once. Patients without a pathology report submitted at any cfDNA collection timepoint or the pathology report did not include ERBB2 (HER2) status, results were inconclusive or quantity not sufficient were excluded. Between March 2014 and April 2017, 1,853 unique patients were identified with reported ERBB2 (HER2) status. For patients with more than one cfDNA timepoint collected (N=349; 18.8%), the earliest pathology report was referenced. 1,386 patient tumor samples were negative for HER2 overexpression (74.8%), 325 (17.5%) were positive, and 142 (7.7%) were equivocal. Twenty-nine of the 1,386 patients with reported tumor negative HER2 status had amplification on subsequent cfDNA analysis (2.1%).

All 29 patients were female. Most patients (N=21) had a single cfDNA timepoint collected. Median age at cfDNA blood draw was 58 years (range 28–68). Median length of time between reported tissue negative status and cfDNA blood draw was 405 days (range 21–4,060). Median plasma ERBB2 copy number was 2.44 (greater than 50th-centile per laboratory data) (range 2.15–16.5).

Clinical follow-up was obtained for 19 patients (65%). Nine patients were lost to follow-up or succumbed to disease prior to initiation of a new therapeutic regimen. One patient was known HER2 positive prior to receipt of the cfDNA results. In the remaining nine patients, six initiated targeted HER2 therapy following receipt of the cfDNA results, with five of six (83%) demonstrating a clinical response. In one patient with known ER/PR positive, HER2 negative disease, progressing through multiple lines of therapy, addition of trastuzumab and pertuzumab to her paclitaxel regimen following identification of the cfDNA ERBB2 amplification resulted in a significant reduction in CEA levels (238 to 37.9 ng/mL) by week five. In a second patient, following identification of the cfDNA ERBB2 amplification, she was treated with trastuzumab and pertuzumab along with docetaxel and had a dramatic response. She continues on trastuzumab and pertuzumab alone.

Although a modest sample size, this is the second cfDNA series demonstrating that ERBB2 (HER2) status may flip from negative to positive upon recurrence or metastasis, and that targeting plasma-detected ERBB2 amplification with anti-HER2 has clinical benefit. cfDNA is a viable alternative to tissue rebiopsy in this patient population.

Citation Format: Raymond VM, Diaz J, Banks KC, Ahn E, Brufsky A, Ellis M, Lippman M, Lee C, Pluard T, Schreeder M, Schwab R, Lanman RB. Cell free DNA analysis identifies actionable ERBB2 amplifications in patients with HER2 negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-02-12.

Abstract GS2-03: Highly recurrent transcriptional remodeling events in advanced endocrine resistant ER-positive breast cancers

BACKGROUND: Although individual cancers are driven by heterogeneous processes, cancer mortality has a near universal cause—therapy resistance, recurrence and metastasis to vital organs. Characterizing more advanced tumors has borne valuable insight into cancer progression, yet studies of longitudinally collected breast cancer specimens are scarce given lengthy periods of cancer dormancy. In this study, we aimed to create the most comprehensive characterization of gene expression alterations to date between patient-matched pairs of primary and advanced ER-positive breast cancers.

MATERIALS/METHODS: Hybrid-capture RNA-sequencing was performed on 50 patient-matched pairs of primary and advanced ER-positive tumors from various recurrence sites (9 brain, 11 bone, 3 GI, 10 ovary, 17 local). Time to recurrence was up to 14.1 years with a median of 3.4 years. A shared variant analysis confirmed all paired samples were patient-matched. 1,380 cancer-related genes were analyzed for outlier expression fold-changes in matched recurrences versus primary tumors. Pair-specific, outlier fold-change thresholds were defined as Q1/Q3 +/- [1.5 X IQR]; using each pairs' fold-change values across all genes as the distribution. These discrete, longitudinal transcriptional remodeling events (LTREs) were assessed for recurrence across all sites and analyzed for enrichments within specific cohorts (Fisher's exact tests), such as locoregional vs. distant recurrences. To determine if LTREs represent acquired vulnerabilities, ex vivo and in vivo experiments targeting a recurrent, druggable LTRE gain of RET was performed.

RESULTS: The majority of advanced cancers were transcriptionally similar to patient-matched primaries with 23 of 33 distant metastases retaining PAM50 assignments of the matched primary—shifts to HER2 (n=4, 12%) or Luminal B (n=5, 15%) subtypes accounted for most metastatic discordances. Despite this intrinsic conservation, remarkably recurrent gene-level LTRE gains and losses were observed in advanced disease. Recurrent LTRE gains included NCAM1 [42%], FGFR4 [40%], IBSP [36%], ROBO2 [36%] and SPP1 [30%]. Notable LTRE losses included RELN [42%] and ESR1 [26%]. NCAM1 LTREs showed the most significant enrichments (p < 0.001) in distant disease (20 of 33, 61%) versus locoregional disease (1 of 17, 6%). A prominent LTRE enriched in brain metastasis (BrM) was RET (p-value = 0.003), expression of which showed outlier gains in 56% of ER-positive BrM. Marked anti-tumor activity was demonstrated with the RET inhibitor cabozantinib in ex vivo explant cultures of patient resected BrMs (n=3) and a BrM patient-derived xenograft.

CONCLUSIONS: Taken together, these results demonstrate profound, recurrent and metastatic site-specific LTREs in advanced breast cancers, which may be essential to our understanding of endocrine-therapy resistance and metastasis. Although current emphasis for longitudinal clinical profiling of tumors is on DNA-level alterations, these results suggest LTREs as a compelling, shared mechanism of cancer progression. Given remarkably high recurrence rates of specific LTREs across multiple cohorts, further preclinical and clinical investigations of LTREs are demanded, especially considering some (i.e. FGFR4 and RET) are readily druggable.

Citation Format: Priedigkeit N, Vareslija D, Basudan A, Watters RJ, Lucas PC, Davidson NE, Blohmer J-U, Denkert C, Machleidt A, Heppner BI, Brufsky AM, Oesterreich S, Young L, Lee AV. Highly recurrent transcriptional remodeling events in advanced endocrine resistant ER-positive breast cancers [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr GS2-03.

Abstract P5-16-01: Documenting and sharing breast cancer knowledge from National Cancer Institute designated comprehensive cancer centers (NCI-CCCs) with community oncologists

Introduction:Tumor boards (TB) at National Cancer Institute Designated Comprehensive Cancer Centers (NCI-CCC) are an important source of multidisciplinary education. Unfortunately, expert knowledge from NCI-CCCs is not systematically documented and made accessible to oncologists in the community. This represents a lost opportunity to capture and share clinical expertise that can impact patient care in community centers. Using an online oncologist-only social network, we sought to demonstrate the feasibility of systematically documenting expert insights from TBs and department conferences at NCI-CCCs in order to expand their reach and provide educational benefit to the greater oncology community.

Methods: A pilot program was developed at the University of Texas MD Anderson Cancer Center (MDACC) to design a process in which discussions at departmental breast cancer conferences would be distilled down to clinical questions and answers (Q&A) and posted on theMednet.org, an online social Q&A website of over 3,800 US oncologists. An educational breast cancer conference was selected during a site visit. A faculty member was selected to distil discussions about patient management from the selected conference into a question that addressed the clinical situation being discussed. After the question was posted, the oncologist leading the discussion answered the question on theMednet. The Q&A was then indexed and stored for easy search retrieval and disseminated in a weekly newsletter to all registered medical oncologists. A detailed manual was created to document operating procedures for implementation at additional institutions.

Results: After developing the process at MDACC, the program was expanded to 2 additional NCI-CCCs- University of Pittsburgh (UPMC) and UCLA. The educational breast cancer conferences selected varied by site and were the new patient planning conference at MDACC, tumor board at UPMC, and multidisciplinary clinic at UCLA. The most significant factor for success was involvement of one faculty member who regularly identified educational questions and additional faculty who posted their answers. Between December 2016 and May 2017, 17 answers to 17 questions were posted and shared with over 1,200 medical oncologists via an email newsletter. All questions were focused on topics not answered by NCCN or ASCO guidelines. The majority of questions focused on management decisions around chemotherapy and endocrine therapy. Answers were viewed by 339 oncologists at 260 institutions in 47 states. This included 190 community practices and 70 academic medical centers.

Conclusion: We developed a process of capturing and sharing expert knowledge at NCI-CCC breast cancer conferences on questions not answered by current guidelines. These discussions are otherwise not documented or shared outside of academic centers. By translating discussions into actionable Q&A on an online oncologist network, we made them easily accessible to oncologists at nearly 200 community practices. Future efforts will be aimed at implementing the program into the breast cancer programs at additional NCI-CCCs.

Citation Format: Kalra M, Karuturi M, Tripathy D, Jankowitz R, McCann K, Brufsky A, Hurvitz S, Bogler O, Housri S, Housri N. Documenting and sharing breast cancer knowledge from National Cancer Institute designated comprehensive cancer centers (NCI-CCCs) with community oncologists [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-16-01.

Abstract P2-10-08: A predictive test for neoadjuvant chemotherapy in breast cancer identifies a subset of triple negative patients with resistant disease and the poorest prognosis

Prediction of pathological complete response (pCR) for neoadjuvant treatment is an area of unmet clinical need, especially for triple negative breast cancer (TNBC) as pCR is correlated with better outcomes. Predicting which patients will have residual disease (RD) provides an opportunity to improve treatment planning. We developed a test to predict which patients are likely to achieve pCR or RD to the standard of care (taxane-based) neoadjuvant chemotherapy using gene expression profiling of 325 previously identified novel biomarkers.

Three microarray datasets were used (GSE22226, GSE25055, and GSE25065) including a total of 594 stage II-III breast cancer patients of which 125 (21%) achieved pCR, and 469 (79%) RD. ER+ tumors were present in 57% of the patients and 52% were PGR+. Almost 90% of the patients were Her2-. Of 231 TNBC, 78 (33.8%) achieved pCR, while 153 (66.2%) RD. Of 303 ER+Her- patients 26 (8.6%) achieved pCR while 277 (91.4%) RD. The cohort was divided into balanced populations with 476 patients used for training (80%) and test (20%) rounds of model development, while 118 patients were reserved as a validation set. Combining a “winnowing” process to remove genes with least predictive power, and hundreds of thousands of step-wise runs, followed by ranking genes based on conditional probabilities, we developed a 17-gene cassette (BA100) which was locked-down in the validation set with ROC (AUC) = 0.818. With a cut-off of 83% sensitivity and 68% specificity (PPV 0.4; NPV 0.94), BA100 achieved a 16% true positive rate (true pCR) and 55% true negative rate (true RD) identifying 76% of the patients who achieved pCR, and 69% of the patients with RD. In TNBC, BA100 classified 29% as true positives (TP), 36% as false positive (FP), 30% true negative (TN), and 4.8% false negative (FN). Kaplan Meier (KM) curves showed a significant difference in 5-year disease-free survival (5Y DFS) between TP and TN (p=0.00453) or FP (p=2.09E-06). However, FP had even worse outcomes than TN patients. To improve the TP rate, additional genes expressed in TNBC plus the original 325 genes were subjected to a second round of gene selection to discriminate between TP and FP, resulting in a 16-gene cassette (BA100.1). With a cut-off of 95% sensitivity and 73% specificity (PPV 0.7; NPV 0.95), applying BA100.1 reduced the FP rates from 24% to 9%, while correctly identifying 88% of RD in the validation set. KM curves showed no significant difference in 5Y DFS between 124 TNBC (53.7%) classified as TN versus 29 TNBC (12.6%) classified as FP, while a significant difference in survival rate was found between TNBC classified as TN vs TP (Cox Proportional Harzard p=8.42e-05).

Taken together, we developed a predictive test consisting of two gene cassettes that accurately identified 71% (88/104) of pCR, and 88% (417/469) of RD patients. Gene cassettes include several transcriptional repressors, PI3K signal transduction, components of telomerase, DNA repair genes, fatty acid metabolism and estrogen-independent proliferation. The test stratified TNBC with differential response to chemotherapy and survival rates so that novel approaches can be used without delay. Further validation will confirm the test utility.

Citation Format: Fournier MV, Chen J, Obenauer J, Goodwin EC, Tannenbaum SH, Brufsky AM. A predictive test for neoadjuvant chemotherapy in breast cancer identifies a subset of triple negative patients with resistant disease and the poorest prognosis [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-10-08.

Abstract P5-21-24: Retrospective assessment of treatment patterns and outcomes associated with palbociclib plus letrozole for postmenopausal women with HR+/HER2– advanced breast cancer enrolled in an early access program

Background: The objective of this study was to evaluate treatment patterns and clinical outcomes among patients who received palbociclib in combination with letrozole (P+L) for the treatment of HR+/HER2–advanced breast cancer (ABC) as part of an Expanded Access Program (EAP) in the United States.

Methods: Data were obtained by a retrospective chart review of patients previously enrolled in the EAP. Complete data from time of initial diagnosis of ABC until the date of chart abstraction (end of follow-up), including the post-EAP period, were obtained. Clinical outcomes assessed included clinical benefit rate (CBR), defined as complete response, partial response, or stable disease for ≥24 weeks from P + L initiation, progression free survival (PFS) and overall survival (OS). Survival outcomes were assessed using the Kaplan-Meier statistical analysis.

Results: Data from 126 patients were included in this analysis. Median age was 62.5 years at EAP enrollment, and a majority of patients were Caucasian (83%). Approximately 25% of patients had de novo metastatic disease. A majority of patients had a performance status of ECOG 0 (56%) or 1 (37%) at EAP enrollment. Visceral disease was present in 71% of patients and 16% had bone-only disease. The majority of patients in this cohort from the EAP were heavily pre-treated, having had up to 5 prior lines of therapy in the metastatic setting prior to initiating P + L therapy; nearly 59% received 3+ prior lines before initiating P + L. Only 11% of patients received P + L as their initial regimen for MBC. At the time of the last available record, 12 patients were still on P + L therapy, an average of 21 months after the start of the EAP program. Nearly 80% of patients had prior AI exposure and 69% had prior chemotherapy. CBR was 33% for the overall sample of patients treated with P + L and 22% in those with 3+ prior lines of treatment. Patients with prior AI exposure in the ABC setting (n=100) had a CBR of 27% while those without prior AI exposure had CBR of 58%. Patients with prior chemotherapy (n=87) had a CBR of 28% and those without prior chemotherapy had CBR of 46%. For the entire cohort, 6- and 12-month PFS rates were 40% and 25% respectively; 12- and 24-month OS rates were 66% and 44%, respectively. Patients receiving 3+ lines of prior therapy had 6- and 12-month PFS rates of 28% and 19%, respectively, and 12- and 24-month OS rates of 59% and 34% respectively.

Conclusions: Our results suggest that the majority of patients enrolled in the EAP program derived benefit from receiving treatment with P + L despite multiple prior lines of treatment and prior endocrine-based therapy, including prior AI. These findings further demonstrate the benefit of treatment with palbociclib combination therapy in HR+/HER2– MBC.

Citation Format: Brufsky A, Davis K, Mitra D, Nagar S, McRoy L, Cotter M, Stearns V. Retrospective assessment of treatment patterns and outcomes associated with palbociclib plus letrozole for postmenopausal women with HR+/HER2– advanced breast cancer enrolled in an early access program [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-21-24.

Abstract P4-08-04: The clinical utility of oncotype Dx for patients with recurrence scores of 10 or less: A value based pathology study of tumor histopathology and outcomes analysis in an integrated delivery and finance health system

Introduction

The majority of publications regarding breast cancer GEPTs rarely supply detailed breast tumor histopathology in their outcome studies. As a result, the cost effective role of clinical risk assessment with histopathology of breast carcinomas tends to be minimized. The aims of this study are to characterize the details of breast tumor histopathology of patients with Oncotype Dx Recurrence Scores (RS) of 10 or less, and determine if Oncotype Dx offers value and clinical utility for patients with these low grade tumors

Methods

A total of 459 patients (18%) with Oncotype Dx RS of 10 or less were retrieved from a registry of 2558 patients with Oncotype Dx results. Patients had five years of follow-up with tumor registry and were treated with endocrine therapy alone. Tissue slides were available to review on 441/459 patients. Recorded details included (1) histopathologic type of carcinoma (2) mitotic score (MS), tubule formation, nuclear pleomorphism and Notttingham histologc (NG) grade. (3) Estrogen (ER) and progesterone (PgR) semiquantitated by Allred Score and Histologic Score (H Score: strong 200-300, moderate 100-199, weak <100). (4) Lymph node status. (5) overall survival and breast cancer specific survival.

Results

Patient ages were 33-92, with mean/median age of 60, and all had endocrine therapy alone. 148 of 441(34%) patients had carcinomas of “special types”, notable for low grade/good prognosis including tubular 22(15%), cribriform 15 (10.1%), papillary 17 (11.5%), and mucinous 28 (21%), along with 63 (42.5%) low grade classic lobular carcinomas and 3 (2%) low grade mixed ductal and lobular carcinomas. All 148 tumors had a MS of 1, were NG1 and had high ER HScores (280 median/263 mean) (Allred Scores 7-8) and high PR HScores (210 median/201 mean) (Allred Scores 6-8). The remaining 293 tumors were ductal carcinomas of no special type (NST), and 261/293 (89%) of these had a MS of 1/NG2. Of the remaining cases, 10 (3%) had a MS of 2/NG2, 18 (6%) had MS of 2/NG3 and four (1%) were MS3/NG3. Estrogen receptor H Score/Allred Score was strong (Allred Score 7-8) in 395/441 (89.6%), moderate in 45 (10.2%) and weak in 1 patient (0.2%). Progesterone HScores were strong in (Allred Score 6-8) 269/441 (76%) and moderate in the remainder. Strong and moderate ER comprised 99.8% of tumors. Thus, tumors with MS1, and NG1, all with ER HScore >200 (Allred Score of 7-8) were enriched in the RS <10, and these features distinguished this group from other tumors with a MS1.

At 5 years, 433 patients (98%) were alive, 8 were dead, 1 from breast cancer due to distant recurrence. The 5-year breast cancer specific survival for this group was 99.7%. [95%CI 98.5-99.9.] 87 cases were accrued in the ongoing prospective study to date. There were 15/87 (17%) cases, 95% of which were correctly identified by pathologists as having an RS <10 using the criteria defined, with sensitivity 95%, specificity 86%, PPV 63% 95% CI(49.76-75.08), NPV 99% 95% CI(90.7-99.78). No patient had a recurrence score >22.

Conclusions

Pathologists can identify these low risk tumors with high accuracy. Oncotype Dx lacks clinical value and utility in this setting.

Citation Format: Dabbs DJ, Serdy K, Onisko A, Clark BZ, Bhargava R, Smalley S, Perkins S, Brufsky AM. The clinical utility of oncotype Dx for patients with recurrence scores of 10 or less: A value based pathology study of tumor histopathology and outcomes analysis in an integrated delivery and finance health system [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-08-04.

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.

Abstract P6-09-14: Prognostic significance of a modified residual disease in breast and nodes (mRDBN) algorithm after neoadjuvant therapy for breast cancer

Background: Patients achieving pathologic complete response to neoadjuvant chemotherapy have excellent disease free and overall survival. For patients with residual disease, the residual disease in breast and lymph node (RDBN) method provides useful prognostic information. RDBN is calculated as follows: 0.2*tumor size (in cm)+lymph node status (0-3) + tumor grade (1-3). pCR, low, intermediate and high risk of recurrence categories correspond to RDBN index of 0, 0.1 to 2.9, 3 to <4.4, and ≥ 4.4, respectively. We hypothesized that the prognostic accuracy of RDBN may be improved by also taking into account the residual tumor cellularity.

Methods: Retrospective review of 614 consecutive patients who underwent neoadjuvant therapy for breast cancer was performed. At our institution, tumor size/volume reduction in the breast is determined using the equation:

Estimated % tumor size reduction = [(pre-therapy clinical size – “revised” pathology tumor size)/pre-therapy clinical size]*100.

“Revised” pathology tumor size is calculated by multiplying the largest dimension of the gross tumor bed by the invasive tumor cellularity of the tumor bed (in comparison to the pre-therapy core biopsy sample). For example, if a 3 cm tumor bed has only 50% cellularity for invasive cancer (in comparison to pre-therapy core biopsy), the revised tumor size is 1.5 cm. Hence, we were able to use the “revised tumor size” for calculating the modified RDBN index (mRDBN). We also used gross tumor bed size for gross RDBN (gRDBN) to compare with mRDBN. mRDBN and gRDBN could be calculated on 459 of the 514 cases. Chi-Square statistical analysis was performed.

Results: Mean follow up was 33.1 months (median 31, range 4-70).

The results are shown in Table 1 & 2.

Table 1. Overall Recurrence and MortalityRDBN Score Category Overall Recurrence Mortality  nn (%)RR95% CI; pn (%)RR95% CI; pmRDBN (n=459)High5829 (50.0)19.63[7.22, 53.40]; p=<0.000118 (31.0)16.24[4.97, 53.10]; p=<0.0001Intermed16433 (20.1)7.9[2.86, 21.78]; p=<0.000115 (9.1)4.79[1.41, 16.21]; p=0.006Low803 (3.8)1.47[0.34, 6.42]; p=0.694 (5.0)2.62[0.60, 11.41]; p=0.23pCR1574 (2.5)REF 3 (1.9)REF gRDBN (n=459)High8131 (38.3)15.02[5.49, 41.09]; p=<0.000119 (23.5)12.28[3.74, 40.26]; p=<0.0001Intermed14932 (21.5)8.43[3.05, 23.26]; p=<0.000116 (10.7)5.62[1.67, 18.89]; p=0.003Low722 (2.8)1.09[0.20, 5.82]; p=12 (2.8)1.45[0.25, 8.51]; p=1pCR1574 (2.5)REF 3 (1.9)REF 

Table 2; Reclassification of gRDBN categoriesgRDBN mRDBN ReclassificationClassificationnLow (%)Intermed (%)High (%)Low7272 (100)0 (0)0 (0)Intermed1498 (5.4)140 (93.9)1 (0.7)High810 (0)24 (29.6)57 (70.4)

Conclusions: Both mRDBN and gRDBN provide prognostic information; however, separation of categories is improved with mRDBN (Table 1). mRDBN reclassified 30% of the high risk-gRDBN patients into intermediate risk category with a recurrence rate of 20%, leaving the 'true' high risk subgroup with a revised recurrence rate of 50% (Table 2). RDBN index also identified a group of low risk patients who have prognosis similar to patients with pCR.

Citation Format: Farrugia DJ, Landmann A, McAuliffe PF, Diego EJ, Johnson R, Bonaventura M, Soran A, Dabbs DJ, Clark B, Lembersky BC, Puhalla SL, Brufsky A, Jankowitz R, Davidson NE, Ahrendt GM, Bhargava R. Prognostic significance of a modified residual disease in breast and nodes (mRDBN) algorithm after neoadjuvant therapy for breast cancer [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 P6-09-14.

Abstract P6-07-07: ESR1 amplification and 5'-3' exon imbalance in metastatic breast cancer

BACKGROUND: Growing evidence indicates that base pair mutations in ESR1 are relatively uncommon in newly diagnosed, treatment-naive breast cancer, but frequently acquired in hormone-resistant metastatic breast cancer (MBC). We and others have recently identified ESR1 gene fusion and amplification in MBC, with the ESR1 fusions generally encompassing AF1 and the DNA binding domain. The genomic break required for gene fusions often results in an imbalance in the DNA copy number of exons around the break. We examined ESR1 amplification and 5' and 3' exon copy number imbalance in MBC.

MATERIALS and METHODS: We designed NanoString DNA hybridization probes against coding and non-coding exons (n=9) in ESR1 and 15 reference probes. We analyzed 128 samples consisting of 61 ER-positive and 44 ER-negative metastases, and 23 primary breast cancers. DNA copy number (CN) was determined using nSolver, with >2.7CN as copy number gain, and >10 as CN amplification. ESR1 CN was calculated by averaging the DNA copy number obtained from all coding exons. The 5'-3' copy number ratio was the average copy number of the 5' exons (3-6) divided by the 3' exons (7-10).

RESULTS: 8 (13%) ER positive metastatic breast cancers showed ESR1 amplification with 5 (8%) having >2.7CN, and 3 (5%) with >10CN. In contrast, in ER-negative metastases, we did not detect any samples with amplification >10CN, and a gain (>2.7 CN) in one case. Similarly, in ER+ primary cancers we did not detect any samples with >10 CN amplifications and 2 samples with CN gain (>2.7 CN). ESR1 showed 5'-3' CN imbalance in 1 primary (5%) and in 5 metastatic (5%) breast cancers. We are currently confirming and expanding these data in a larger dataset.

CONCLUSIONS: In addition to ESR1 mutations, ESR1 CN amplifications and 5'-3' imbalance are represent frequent occurrences in endocrine resistant breast cancer. Future studies are aimed at understanding whether the observed exon imbalances are associated with generation of fusion proteins, and whether and how ESR1 amplifications cause changes in endocrine treatment response.

Citation Format: Oesterreich S, Basudan A, Preideigkeit N, Hartmaier RJ, Bahreini A, Gyanchandani R, Leone JP, Lucas PC, Hamilton RL, Brufsky AM, Lee AV. ESR1 amplification and 5'-3' exon imbalance in metastatic breast cancer [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 P6-07-07.

Abstract P2-05-14: Prognostic impact of genomic risk stratification with breast cancer index in patients with clinically low risk, hormone receptor-positive, node-negative, T1 breast cancer

Background: Tumor size and nodal status are prognostic for risk of both early and late disease recurrence in patients with early stage, HR+ breast cancer, and are incorporated into both adjuvant chemotherapy and extended endocrine therapy treatment decisions. In a recent EBCTCG meta-analysis of over 46,000 patients [Pan H, et al. J Clin Oncol 34, 2016 (suppl; abstr 505)], risk of late distant recurrence was assessed in patient subsets based on nodal status and tumor size. Patients with T1N0 disease who were treated with 5 years endocrine therapy had a good overall prognosis, with 4%, 9%, and 14% risk of distant recurrence from years 5-10, 5-15, and 5-20, respectively. Breast Cancer Index (BCI) has been validated as prognostic biomarker for risk of both early and late distant recurrence in multiple randomized trial cohorts. The aim of this analysis was to assess distant recurrence (DR) risk stratification with BCI in patients with clinically low-risk T1N0 tumors.

Methods: Primary tumor samples from the subset of patients with T1N0 disease from 2 independent validation cohorts of HR+ breast cancer patients were examined [Stockholm randomized controlled trial (N=259) and a retrospective multi-institutional cohort (N=237)]. Patients in the Stockholm RCT cohort were treated with adjuvant tamoxifen only; patients in the multi-institutional cohort were treated with adjuvant tamoxifen +/- chemotherapy (20.3%). No patients received extended endocrine therapy. Kaplan-Meier analysis was used to assess the risk of DR within distinct BCI risk groups. Time dependent analysis was performed by combining BCI Low and Intermediate risk groups for risk of early recurrence (0-5y), and BCI Intermediate and High risk groups for risk of late recurrence (>5y).

Results: In the Stockholm cohort, BCI identified 13% of T1N0 patients as high risk for relapse within the first 5y, and these patients had a significantly reduced distant recurrence-free survival (DRFS, 85.3%) compared to BCI Low Risk patients (97.7%; P=0.0004). In patients disease-free at year 5, BCI identified 32% of patients as high risk for late recurrence; these patients had significantly lower DRFS (86.7%) between years 5-15 compared to BCI low risk patients (95.4%; P=0.0263). In the multi-institutional cohort, 22% of T1N0 patients were identified by BCI as high risk for relapse within the first 5y, and these patients had a significantly reduced DRFS (77.3%) compared to BCI low risk patients (96.2%; P<0.0001). In patients disease-free at year 5, 36% of patients were identified by BCI as high risk for late recurrence, with significantly lower DRFS (89.6%) between years 5-10 compared to BCI Low Risk patients (98.4%; P=0.008).

Conclusions: HR+ Patients with favorable clinical features (T1N0) have a good overall prognosis. However, results of this study demonstrated that adding molecular resolution on tumor biology with BCI identified a significant subset of women with higher risk of both early and late distant recurrence; findings support consideration of genomic classification in T1N0 patients to identify additional candidates for adjuvant chemotherapy and/or extended endocrine therapy, respectively.

Citation Format: Schroeder BE, Zhang Y, Stal O, Fornander T, Brufsky A, Sgroi DC, Schnabel CA. Prognostic impact of genomic risk stratification with breast cancer index in patients with clinically low risk, hormone receptor-positive, node-negative, T1 breast cancer [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 P2-05-14.

Abstract OT2-01-02: COLET: A multistage, phase 2 study evaluating the safety and efficacy of a doublet regimen of cobimetinib (C) in combination with paclitaxel (P) or triplet regimens of C in combination with atezolizumab (atezo) plus either P or nab-paclitaxel (nab-P) in metastatic triple-negative breast cancer (TNBC)

Preclinical data suggest that upregulation of the MAPK pathway confers resistance to taxane chemotherapy. Mutations and gene amplifications in the MAPK pathway are present in many TNBC tumors and may contribute to taxane resistance. Preliminary data from an initial safety run-in stage of the COLET study (ClinicalTrials.gov ID, NCT02322814; EudraCT number, 2014-002230-32) suggest improvement of clinical outcomes when MEK inhibition is combined with taxane chemotherapy. Additionally, in preclinical models, MEK inhibition was shown to enhance anti–PD-L1 activity. The monoclonal antibody PD-L1 inhibitor atezo has shown promising activity in combination with nab-P in metastatic TNBC. Accordingly, the COLET protocol was amended to include the evaluation of triplet regimens combining atezo with MEK inhibition and taxane chemotherapy[SL1] . COLET is evaluating the safety and efficacy of various combinations of C as first-line treatment for metastatic or locally advanced TNBC. Key eligibility criteria include measurable disease per Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST v1.1) and left ventricular ejection fraction > institutional lower limit of normal or >50%. Neoadjuvant or adjuvant therapy is allowed if completed >6 months prior to study entry. COLET has 3 cohorts: I, II, and III. Cohort I has 2 stages: an initial safety run-in stage (n∼12) followed by an expansion stage (n∼90) of 1:1 randomization to C + P or placebo (PBO) + P. Patients received P 80 mg/m2 on days 1, 8, and 15 and C/PBO 60 mg/day on days 3-23 of each 28-day cycle. In the expansion stage of Cohort I, randomization is stratified by prior neoadjuvant/adjuvant taxane therapy and disease-free interval from last chemotherapy dose. Cohorts II and III will evaluate the safety and efficacy of adding atezo to C + P or nab-P, respectively. Each cohort has a safety run-in stage (n∼15) and an expansion stage (additional n∼15); each will receive atezo 840 mg on days 1 and 15 and C 60 mg/day on days 3-23 of every 28-day cycle. Cohort II will receive P 80 mg/m2 and Cohort III will receive intravenous nab-P 100 mg/m2 on days 1, 8, and 15. Patients will receive treatment until disease progression or toxicity. The primary efficacy end point is investigator-assessed progression-free survival (PFS) for the expansion stage (Cohort I), and the primary PFS analysis will be performed when 60 PFS events occur across the 2 arms. This provides 77% power to detect a hazard ratio of 0.5 at a two-sided significance level of 0.05. For Cohorts II and III, the primary efficacy end point is overall response rate per RECIST v1.1; secondary end points include duration of response, PFS, and overall survival. Recruitment into the safety run-in stage of Cohort I is complete. Accrual into the randomization stage of Cohort I and the initial safety run-in stage of Cohorts II and III are ongoing. Patients from sites across North America, Europe, and the Asia-Pacific region will be enrolled.

Citation Format: Miles D, Kim S-B, McNally V, Simmons B, Wongchenko M, Xu N, Brufsky A. COLET: A multistage, phase 2 study evaluating the safety and efficacy of a doublet regimen of cobimetinib (C) in combination with paclitaxel (P) or triplet regimens of C in combination with atezolizumab (atezo) plus either P or nab-paclitaxel (nab-P) in metastatic triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr OT2-01-02.

Abstract P2-09-15: A multi-institutional, prospective study of incorporating the genomic platform breast cancer index as a tool for decision-making regarding extension of adjuvant endocrine therapy

Background: Extending adjuvant endocrine therapy (AET) for hormone responsive breast cancer (HRBC) from 5 to 10 years is beneficial for many in preventing late relapse. Current decision-making regarding extension relies on a decision-making process that weighs non-personalized recurrence risks against risks and benefits of extended AET. The Breast Cancer Index (BCI, BioTheranostics Inc) has been validated to quantify the risk of late recurrence and to predict likelihood of benefit from AET extension based on an individual's tumor genomic profile. The purpose of this study was to conduct a multi-institutional study to prospectively assess the impact of BCI i) on provider's recommendation using the BCI results; 2) the confidence with decision-making; and 3) patient's satisfaction regarding extension of AET.

Methods: Patients with stage I-III HRBC treated at Yale Cancer Center and University of Pittsburgh Medical Center (UPMC), who had completed at least 3.5 years of AET were eligible. BCI was performed on FFPE samples from the original tumor sample (bioTheranostics Inc.). Patients and physicians completed pre- and post-test questionnaires examining preferences for extending AET, patients also completed anxiety and decision-conflict surveys.

Results: 140 patients [mean age 61, 80% postmenopausal, 73% stage I] were included. No extended AET was recommended for 35.3% patients' pre-testing. Reasons physicians did not recommend extended AET were perceived low risk of recurrence (87%), risk of osteoporosis (25%) and side effects (13%). Extended therapy was recommended for 65.7% patients pre-testing. Integration of BCI resulted in a change in physician treatment recommendation in 29% of patients. The recommendation for no extended AET rose to 48% and recommendation for extended AET dropped to 52% (OR=1.76 95% CI 1.08-2.85; p=.003). Of the recommendations that changed (N=41), the majority (73%) was for not extending endocrine therapy. However, 27% of recommendations were to extend endocrine therapy because of high risk or high likelihood of benefit results. More physicians felt strongly confident in their recommendation after the test result (26.4%) than before (9.3%) (OR= 3.5 95% CI 1.77-6.95; p<.0001). Satisfaction of decision increased in 23% of patients (OR=2.72 95% CI 1.66-4.46; p<.0001). Patient reported concerns including the cost, safety and benefit of extended AET decreased from pre- to post-testing (p=.025; p<.0001; p=.0012 respectively)

Conclusions: Overall, incorporation of BCI into clinical practice resulted in significant changes in physician recommendations regarding AET duration, with the majority of recommendations for no extended AET. Physicians reported increased confidence for their recommendation when incorporating the test result. There was also a significant increase in patient satisfaction and decrease in patient reported concerns regarding cost, safety and benefit of extended AET. The BCI is a tool that could be incorporated into decision-making algorithms to enhance physician confidence and patient satisfaction with recommendations for extending AET.

Citation Format: Sanft T, Berkowitz A, Schroeder B, Hatzis C, Schnabel C, Aktas B, Brufsky A, Pusztai L, vanLonden GJ. A multi-institutional, prospective study of incorporating the genomic platform breast cancer index as a tool for decision-making regarding extension of adjuvant endocrine therapy [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-09-15.

Abstract PD1-05: Breast cancer brain metastases show limited intrinsic subtype switching, yet exhibit acquired ERBB2 amplifications and activating mutations

BACKGROUND: Metastasis is the major cause of mortality in breast cancer (BrCa) patients. Our understanding of brain metastasis (BrM) is limited, reflected by a lack of effective treatments. We aimed to (1) determine BrCa gene signature differences between primary tumors and matched BrM and (2) uncover BrM-specific alterations that may be clinically actionable.

MATERIALS and METHODS: NanoString expression profiling of 127 genes from 5 major prognostic tests (MammaPrint, EndoPredict, PAM50, OncotypeDX, MGI) was performed on 20 patient-matched primary (10 ER-neg, 10 ER-pos) and metastatic brain tumors. Subtype classification was performed using genefu. Protein changes in ER and HER2 (ERBB2) were confirmed by IHC. BrM-specific ERBB2 gains were corroborated in a publicly available dataset of 18 additional patient-matched cases (dbGAP phs000730.v1.p1). To test whether ERBB2 amplification and base pair mutation is metastasis-site specific, we further analyzed an expanded cohort of 7,884 breast tumors enriched for metastatic samples (52%) including liver (16.7%), lung (4.3%), bone (3.6%), and brain (2.0%) using comprehensive hybrid-capture sequencing of ERBB2.

RESULTS: 17/20 BrM retained the PAM50 subtype of the primary BrCa. Despite this concordance, 17/20 BrM harbored expression changes (< or > 2-fold) in clinically actionable genes including gains of FGFR4 (30%), FLT1 (20%), AURKA (10%) and loss of ESR1 expression (45%). The most recurrently upregulated gene was ERBB2, showing a >2-fold expression increase in 35% of BrM. 3 of 13 (23.3%) cases originally HER2-negative, and thus HER2-therapy naive, in the primary BrCa were IHC-positive (3+) in the paired BrM with an observed metastasis-specific amplification of the ERBB2 locus. In an independent dataset, 2 of 9 (22.2%) HER2-negative BrCa switched to HER2-positive with one BrM acquiring ERBB2 amplification and the other showing metastastic enrichment of the activating V777L ERBB2 mutation. Analysis of a large cohort of breast tumors (n=7,884) showed that across all organs ERBB2 amplification and/or base pair mutation was similar (p=0.18) between primary (13%) and metastatic disease (12%), however, a strong and significant enrichment was seen for BrM (primary 13% vs BrM 24%, p<0.0005).

CONCLUSIONS: Taken together, these results demonstrate that the majority (85%) of patient-matched BrM retain the intrinsic subtype of the primary cancer. However, despite this transcriptional similarity, alterations in clinically actionable genes are common, with BrM acquiring ERBB2 amplifications and/or base pair mutations at a frequency of ∼20%, even in HER2-therapy naive tumors. In a large cohort of primary and metastatic breast cancers, there is also a unique enrichment for ERBB2 alterations in BrM. This study provides a strong rationale to molecularly profile metastatic lesions to both better understand biological mechanisms of metastases and to perhaps refine therapeutic decision-making in advanced cancers.

Citation Format: Priedigkeit N, Hartmaier RJ, Chen Y, Vareslija D, Basudan A, Thomas R, Leone JP, Lucas PC, Bhargava R, Hamilton RL, Chmielecki J, Davidson NE, Oesterreich S, Brufsky AM, Young L, Lee AV. Breast cancer brain metastases show limited intrinsic subtype switching, yet exhibit acquired ERBB2 amplifications and activating mutations [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 PD1-05.

Abstract P6-11-03: A phase 2 open-label study of lucitanib in patients (pts) with FGF aberrant metastatic breast cancer (MBC)

BACKGROUND: Lucitanib is a potent, oral antiangiogenic tyrosine kinase inhibitor of Vascular Endothelial Growth Factor Receptors 1-3 (VEGFR1-3), Platelet-Derived Growth Factor Receptors alpha and beta (PDGFRα/β), and Fibroblast Growth Factor Receptors 1-3 (FGFR1-3). FGF aberrancies (amplification of FGFR1,or 11q[amplicon containing FGF ligands 3, 4, and 19]), are genomic alterations observed in over 20% of breast cancer pts and promote cancer proliferation and survival.

METHODS: MBC pts who had received at least 1 metastatic line of therapy were randomized 1:1 to 10 or 15 mg QD of lucitanib. Stratification was based on local assessment of FGF aberrancy; pts with both FGFR1 and 11q-amplified tumors were stratified as FGFR1 amplified. Central confirmation of FGFR1 or 11q amplification was done using Abbott FISH probes (FGFR1 or 11q copy number ≥ 6 and a ratio of FGFR1 or 11q to centromere ≥ 2). Investigator-assessed progression-free survival (PFS) was the primary endpoint. Secondary endpoints included objective response rate (ORR) per RECIST 1.1, disease control rate (DCR), duration of response (DR), and incidence of treatment-emergent adverse events (TEAE).

RESULTS: Enrollment completed in 3/2016; 178 pts that received at least 1 dose of lucitanib are included in this analysis (baseline characteristics in Table 1). Due to grade 3 hypertension in the 15 mg group (46% vs 37% in 10 mg group), enrollment to the 15 mg group was halted. Overall, most pts (97%) experienced at least 1 TEAE, with the most frequently (≥ 30%) occurring events being hypertension (73%), fatigue (48%), nausea (43%), hypothyroidism (40%), and headache (33%). Grade ≥ 3 TEAEs occurred in 66% of pts, with hypertension as the most frequent event (40%) followed by proteinuria and hyponatremia (both 6%). AEs were manageable with dose interruption or reduction, with approximately 8% of pts ending treatment due to an AE. Current median PFS is 3.5 mos (95% CI 2.8-4.6; range 0.62-12.95) and 2.6 mos (95% CI 1.8-2.9; range 0.82-18.87) respectively for the 10 mg and 15 mg treatment groups. No differences in clinical activity were observed by treatment group, FGF aberrancy, hormone receptor or HER2 status. Of the 168 evaluable pts, confirmed ORR was 3%; overall DCR was 27% (32% for pts in the 10 mg group compared to 20% for the 15 mg group); overall mean (standard deviation) DR of 3.3 (1.8) mos.

Baseline Characteristics 10 mg QD15 mg QD N=109N=69Age (years)Median5653Range27-8227-80SexFemale109 (100%)67 (97%)Male02 (3%)ECOG PSmissing5 (5%)2 (3%)051 (47%)30 (43%)153 (49%)37 (54%)Number of prior anticancer therapies in the metastatic setting> 332 (29%)21 (30%)3-648 (44%)32 (46%)> 629 (27%)16 (23%)Endocrine/HER2 statusmissing7 (6%)1 (1%)ER+ or PR+74 (68%)50 (73%)HER2+12 (11%)7 (10%)TNBC16 (15%)11 (16%)FGFR aberrancyFGFR1 amplified54 (49%)29 (42%)11q amplified31 (28%)24 (35%)FGFR1 and 11q amplified13 (12%)9 (13%)FGFR1 and 11q non-amplified11 (10%)7 (10%)

CONCLUSION: At 10 mg QD, lucitanib has modest activity with manageable toxicity in this heavily pretreated pt population. Future clinical development for lucitanib may focus on alternative biomarkers to identify sensitive tumors and rational combinations with other anti-cancer drugs.

Citation Format: Mayer IA, Arteaga CL, Nanda R, Miller KD, Jhaveri K, Brufsky AM, Rugo H, Yardley DA, Vahdat LT, Sadeghi S, Audeh MW, Rolfe L, Litten J, Knox A, Raponi M, Tankersley C, Isaacson J, Wride K, Morganstern DE, Vogel C, Connolly RM, Gradishar WJ, Patel R, Pusztai L, Abu-Khalaf M. A phase 2 open-label study of lucitanib in patients (pts) with FGF aberrant metastatic breast cancer (MBC) [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 P6-11-03.

Abstract P4-22-22: Cobimetinib (C) combined with paclitaxel (P) as a first-line treatment in patients (pts) with advanced triple-negative breast cancer (COLET study): Updated clinical and biomarker results

Resistance to standard taxane-based chemotherapy is common in triple-negative breast cancer (TNBC). Mutations and gene amplifications in the MAPK pathway that upregulate MAPK signaling are present in many TNBC tumors. Upregulation of the MAPK signaling pathway can result in degradation of the pro-apoptotic protein BIM and upregulation of anti-apoptotic proteins, including BCL-2, BCL-XL, and MCL-1, thus promoting cell survival and desensitizing tumor cells to the pro-apoptotic effects of taxane chemotherapy. Updated data on clinical safety and efficacy are presented along with biomarker data evaluating the effects of treatment on induction of apoptosis.The COLET study (ClinicalTrials.gov ID, NCT02322814; EudraCT number, 2014-002230-32) consisted of a safety run-in (n∼12) followed by a blinded 1:1 randomized expansion stage (n∼90) to C + P or placebo (PBO) + P. The safety stage is complete and the randomized stage is enrolling pts. Two additional cohorts investigating the effect of adding atezolizumab will be recruiting and are out of scope of this submission. Pts in cohort I were treated with P 80 mg/m2 on days 1, 8, and 15 and C/PBO 60 mg/day on days 3–23 of each 28-day cycle until disease progression or unacceptable toxicity. Gene expression and apoptotic index were measured by RNA-Seq and TUNEL staining, respectively, to assess the biologic activity of C + P.Sixteen women (median age, 55.5 years) were enrolled in the safety run-in stage. At data snapshot (April 22, 2016), all 16 pts had received ≥1 dose of study treatment. Median time on treatment was 116 days (range, 7-336) for C and 84 days (range, 0-351) for P. Fifteen (94%) pts had ≥1 adverse event (AE); 5 (31%) pts had grade 1/2 AEs and 10 (63%) pts had grade 3 AEs (Table). No pts experienced grade 4–5 AEs. Among the 16 safety run-in patients, responses to date include partial response (PR; n = 8 [50.0%]), stable disease (SD, n = 4 [25.0%]), and progressive disease (n = 2 [12.5%]), as well as 2 pts with no post-baseline tumor assessment. Six pts maintained a PR at ∼20 weeks and three maintained a PR at ≥40 weeks. To date, matched pre- and on-treatment biopsies were evaluable for 2 pts, 1 with a PR and 1 with SD. In the patient who attained a PR, increased expression of pro-apoptosis genes, including BIM, was observed; but this was not seen in the patient experiencing SD. The PR patient also had an increase in apoptotic index. Updated biomarker data will be reported.This is the first study to evaluate C + P in TNBC. The safety profile of C + P is consistent with that of known safety profiles. Efficacy and safety will be further evaluated in the ongoing randomized stage.

Most common (any grade ≥20%) AEsTreatment-emergent AEs, n (%)C + P (safety run-in stage), N = 16 All gradesGrade 3Diarrhea10 (63)1 (6)Rash8 (50)0Nausea7 (44)0Alopecia5 (31)0Blood CPK level increase5 (31)1 (6)Stomatitis4 (25)2 (13)Asthenia4 (25)1 (6)Constipation4 (25)0Dyspnea4 (25)0Edema peripheral4 (25)0Pyrexia4 (25)0Vomiting4 (25)0AEs, adverse events; C, cobimetinib; CPK, creatinine phosphokinase; P, paclitaxel.

Citation Format: Brufsky A, Kim S-B, Velu T, García-Saenz JA, Tan-Chiu E, Sohn JH, Dirix L, Borms MV, Liu M-C, Moezi MM, Kozloff MF, Sparano JA, Xu N, Wongchenko M, Simmons B, McNally V, Miles D. Cobimetinib (C) combined with paclitaxel (P) as a first-line treatment in patients (pts) with advanced triple-negative breast cancer (COLET study): Updated clinical and biomarker results [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-22-22.

Abstract P4-13-05: Safety results of the US expanded access program (EAP) of palbociclib in combination with letrozole as treatment of post-menopausal women with hormone-receptor-positive (HR+), HER2-negative (HER2-) advanced breast cancer (ABC) for whom letrozole therapy is deemed appropriate

Background: In the Phase I/II PALOMA-1 trial, a study in women with estrogen receptor (ER) positive advanced breast cancer (ABC) receiving initial therapy for their metastatic disease, combination of the CDK4/6 inhibitor palbociclib with letrozole improved progression free survival compared to letrozole. The aim of this open-label, single-arm EAP was to provide appropriate patients (pts) with ABC access to palbociclib pending marketing approval in the United States.

Methods: In the EAP, a total of 242 pts with HR+/HER2- ABC were treated at 42 sites in the US. Pts received palbociclib 125 mg/d (3 weeks on, 1 week off) in combination with letrozole 2.5 mg/d (continuous daily dosing) until disease progression, intolerable adverse event (AE), or commercial availability. AEs and serious AEs (SAEs) were assessed every cycle. Complete blood counts were assessed on day 1 and day 14 of the first two cycles and then at the beginning of each cycle thereafter. Tumor assessments were collected by investigators as per routine clinical practice.

Results: In this early analysis, we describe an initial cohort of 97 pts, with data collected during the first 3 months of study. Median duration of therapy was 31 days. Mean age was 62 yr (range 29-89). Baseline ECOG PS was 0, 1 or 2 in 36%, 49%, and 14% of pts, respectively. Common prior treatments (≥40% in any setting) included fulvestrant (59%), anastrozole (50%), paclitaxel (50%), exemestane (48%), cyclophosphamide (46%), tamoxifen (45%), doxorubicin (44%), and capecitabine (40%). Treatment-emergent AEs (TEAE; all grades) that occurred in greater than 10% of patients included neutropenia (28%), fatigue (19%), neutrophil count decreased (12%). Other hematologic TEAE rates included: anemia 9%, white blood cell count decreased 9% and thrombocytopenia 5%. All causality SAEs occurred in 6% of pts at the rate of 1 patient each for ankle fracture, constipation, disease progression, febrile neutropenia, lung infection, and pancytopenia. The rate of palbociclib dose reduction due to a TEAE was 4%. The rate of temporary delay of palbociclib due to TEAE was 36%. TEAEs leading to permanent discontinuation occurred in 1% of pts (Grade 3 nausea & vomiting). Grade 3 or 4 TEAEs were reported in 42% of pts, including neutropenia (Grade 3: 24%, Grade 4: 2%). There were no fatal outcomes due to TEAEs. This early data will be updated for final conference presentation to include the complete patient cohort and updated duration of therapy on study drug.

Conclusions: In this population of pts with HR+/HER2- ABC, palbociclib in combination with letrozole was well tolerated. Analysis of this early cohort indicates that the safety profile was consistent with that seen in the PALOMA-1 trial.

Clinical trial information: NCT02142868

Funding Source: Pfizer.

Citation Format: Stearns V, Smith II JW, Patel R, Lu D, Perkins JJ, Cotter MJ, Brufsky AM. Safety results of the US expanded access program (EAP) of palbociclib in combination with letrozole as treatment of post-menopausal women with hormone-receptor-positive (HR+), HER2-negative (HER2-) advanced breast cancer (ABC) for whom letrozole therapy is deemed appropriate. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-05.

Abstract S6-04: Patient-reported outcome (PRO) results, NRG Oncology/NSABP B-35: A clinical trial of anastrozole (A) vs tamoxifen (tam) in postmenopausal patients with DCIS undergoing lumpectomy plus radiotherapy

Background

The clinical results of NSABP B-35, phase III trial comparing 1 mg/day A to 20 mg/day tam, each given for 5 years, were reported at ASCO 2015. B-35 demonstrated a statistically significant benefit in breast cancer free interval for women assigned to A, primarily in women <60 years. A secondary endpoint of B-35 was quality of life (QOL) and symptom (SX) outcomes in the two treatment groups. The primary hypotheses of the PRO study were that there would be no differences in QOL between the two treatments, and that patients receiving A would report higher rates of hot flashes compared to patients receiving tam. Other SX comparisons were secondary endpoints.

Methods

QOL and SX were assessed at baseline (prior to randomization), and every 6 months thereafter for 5 years of treatment and in the following 12 months. QOL was measured with the SF-12 Physical Component Summary (PCS) and Mental Component Summary (MCS). SX were measured with selected scales from the BCPT symptom-checklist, and other standardized instruments. Stratification was by age (<60 v ≥60) as in the main trial. Study hypotheses and endpoints were examined by comparing PROs in the two treatment arms using a mixed model for repeated measures analysis with adjustment for the baseline scores, time point and age category, using an intention-to-treat principle and including only patients who completed the baseline and at least one follow-up questionnaire. Patients with protocol events were censored. Only data through 60 months are reported here. The accrual goal for the sub-study was 1,150 consecutive patients.

Results

Between January 6, 2003 and June 15, 2006, a total of 3,104 patients were entered and randomly assigned to NSABP Protocol B-35. Accrual to the PRO study of B-35 closed on December 28, 2004, at which time 1,275 patients were entered, with 1,193 patients included in this analysis. There were no medical or demographic differences between patients assigned to A or tam in the PRO sub-study, and they reflected the characteristics of the parent trial. Adherence to data collection across the 60 months was 87%. There were no significant differences in QOL outcomes by treatment for the PCS (p=0.16) or the MCS (p=0.38). SX subscales: hot flash scale was greater in tam group and this difference varied over time (p=0.001); musculoskeletal pain was significantly greater in A group for time points 6-24 months (all p<.001); vaginal problems were greater in A group (p=0.03). Hot flash and vaginal problems were significantly worse in women <60 years. Additional SX outcomes (depression, fatigue, sexual function) will be reported at presentation.

Conclusion

In this large, double-blind, placebo-controlled trial comparing A to tam in patients with DCIS, there was no significant difference in QOL between the two treatments. However, there were important treatment differences in SX outcomes, which should be considered as part of treatment decision-making discussions, along with the clinical breast cancer outcome results.

Support: CA-180868, 180822, 189867, 196067, 114732; AstraZeneca Pharmaceuticals LP.

Citation Format: Ganz PA, Cecchini RS, Julian TB, Margolese RG, Costantino JP, Vallow LA, Albain KS, Whitworth PW, Cianfrocca ME, Brufsky A, Gross HM, Soori GS, Hopkins JO, Fehrenbacher L, Sturtz K, Wozniak TF, Seay TE, Mamounas EP, Wolmark N. Patient-reported outcome (PRO) results, NRG Oncology/NSABP B-35: A clinical trial of anastrozole (A) vs tamoxifen (tam) in postmenopausal patients with DCIS undergoing lumpectomy plus radiotherapy. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr S6-04.

Abstract P6-08-02: Developing in vitro models of ductal carcinoma in situ from primary tissue

BACKGROUND: Because there are currently no reliable predictors for progression of ductal carcinoma in situ (DCIS) to invasive disease, nearly all patients receive aggressive therapy, leading to over-treatment in many cases. Few in vitro models for studying DCIS progression have been developed. We report here the successful culture and expansion of primary DCIS from surgical specimens using a conditional reprogramming protocol.

MATERIALS AND METHODS: From 2/2014 to 4/2015, patients with percutaneous core needle biopsy demonstrating DCIS were enrolled in a tissue banking protocol after informed consent was received. Under supervision of the surgical pathologist, fresh tissue measuring between 5-15 mm in length was taken from lumpectomy or mastectomy specimens. Tissue was divided such that half was mechanically and enzymatically dissociated and then cultured in medium conditioned by irradiated mouse fibroblasts and supplemented with rho-associated protein kinase (ROCK) inhibitor, and the second half, known as the "mirror image" remained as part of the clinical specimen.

RESULTS: Of 49 consented patients, mean age was 59 ± 10 years. 7 were excluded due to final pathology not consistent with DCIS: 4 upstaged to invasive ductal cancer, 2 had microinvasion and 1 showed pleomorphic lobular carcinoma in situ. Of the remaining 42, 9 were failures: 5 tissues were not received in lab and 4 cases were received, but no cells grew in culture. Of the remaining 33 cases of DCIS, 70% (n=23) and 27% (n=9) were nuclear grade 2 and 3 respectively. 91% (n=30) were ER-positive, with H-score ranging between 4 and 300. 19 (58%) were expanded in cell culture for up to two months in culture, and 14 were frozen immediately after mechanical dissociation for future growth. The 19 cell cultures could be cryopreserved and expanded. The cultures are almost exclusively composed of cytokeratin 8- and EpCAM-positive luminal cells and cytokeratin 14-, cytokeratin 5-, and p63-positive basal mammary epithelial cells, suggesting maintenance of heterogeneity in vitro. Furthermore, as assessed by luminal and basal marker expression, these cells retain their cellular identities both in the "conditionally reprogrammed" proliferative state and when conditioned media and ROCK inhibitor were withdrawn. When grown to 100% confluency, the cultures appear to organize into luminal and basal layers as well as luminal compartments surrounded by basal cells.

CONCLUSION: Primary cultures of DCIS derived directly from patient tissues may serve as in vitro models for the study of DCIS.

Citation Format: McAuliffe PF, Brown DD, Oesterreich S, Lee AV, Johnson RR, McGuire KP, Davidson NE, Brufsky AM, Dabbs DJ. Developing in vitro models of ductal carcinoma in situ from primary tissue. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-08-02.

Abstract P1-11-06: The experience of caregivers of women with metastatic breast cancer: Insights from the Make Your Dialogue Count survey

Introduction: Caregivers of patients with breast cancer have demonstrated persistent unmet needs, including reduced physical and psychosocial well-being. This may be particularly acute in caregivers of patients with metastatic breast cancer (MBC), whose ongoing treatments and increasing disability with disease progression offer particular challenges. While prevalence of MBC is currently unknown, caregivers of women with MBC represent a sizable group.

Objective: To explore the emotional, psychological, and social impact on caregivers of patients with MBC and to identify gaps in communications between patients and their caregivers and oncologists.

Methods: The "Make Your Dialogue Count" survey was conducted online, by paper, and by telephone (June-August 2014) among caregivers in the United States (age ≥18 y) who attended ≥50% of doctor visits of women with MBC (age ≥21 y). Survey responses were single- or multiple-response, numeric text, or rated on a 4-point Likert scale. Caregiver data were unweighted and representative only of those responding. Statistically significant differences between groups were determined by standard t-test of column proportions and means at the 95% confidence level.

Results: 234 caregivers responded; 73% were men, 44% were the patient's spouse/partner, and 27% were nonwhite. Median age was 44 y. The caregivers' loved ones had a median time from initial breast cancer diagnosis of 44 months prior, and 51% had recurred after early breast cancer. Most caregivers (76%) considered themselves to be extremely or very involved in treatment decisions, but a sizable fraction of caregivers were unaware of the HR (20%) or HER2 (29%) status of the patient's cancer, indicating a lack of basic information needed for informed decision-making. While most (93%) said they felt comfortable speaking with the treatment team about MBC treatment, 41% reported communication barriers. Over half of caregivers (53%) felt that nobody understands what they're going through, and most (86%) reported that their lives had been negatively affected in some way (such as sleep habits, relationships and social life, hobbies and personal time, and financial stability and employment). Most caregivers considered caregiving to be an emotional (77%) and physical (56%) burden and 36% felt unappreciated. At the time of initial MBC diagnosis, 69% of caregivers felt it was important/very important for their loved one's doctor to refer them to support services, but only 25% of caregivers reported receiving such a referral. Subgroup analysis of caregiver's gender revealed some differences in responses relating to communications with oncologists, treatment experience, and emotional impact.

Conclusions: While committed to their roles, these caregivers often found their role to be a physical and emotional burden, and many reported feeling isolated and unappreciated for their caregiving. Our findings indicate a strong need for support services specifically tailored to caregivers, including outreach to address emotional, financial, and practical needs stemming from caring for a loved one with MBC. They also indicate a need for improved disease and treatment information exchange between caregivers, patients, and healthcare providers.

Citation Format: Mayer M, Sampayo I, Bell Dickson R, Citron ML, Brufsky AM. The experience of caregivers of women with metastatic breast cancer: Insights from the Make Your Dialogue Count survey. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-11-06.

Abstract OT1-03-18: COLET: A multistage, phase 2 study evaluating the safety and efficacy of cobimetinib in combination with paclitaxel as first-line treatment for patients with metastatic triple-negative breast cancer

Background: Cobimetinib (cobi) is a potent, highly selective inhibitor of MEK that has shown benefit when administered in combination with the BRAF inhibitor vemurafenib in BRAFV600-mutated metastatic melanoma. Preclinical data suggest that up-regulation of the MAPK pathway is a potential resistance mechanism against taxane chemotherapy. Clinically, the combination of MEK inhibition and taxane chemotherapy in non–small cell lung cancer patients (pts) has improved response rate (RR) and progression-free survival (PFS). Because most triple-negative breast cancer (TNBC) pts develop resistance to taxane chemotherapy and because genetic alterations (including mutations and gene amplifications) in the MAPK pathway are present in many TNBC tumors, the combination of taxane chemotherapy and MEK inhibition could be an effective treatment option.

Study design: COLET (WO29497) is a multistage study designed to evaluate the safety of and to estimate the efficacy of cobi  paclitaxel in pts with metastatic or locally advanced TNBC who have not previously received systemic therapy for metastatic disease. The study will be conducted in 2 stages: an initial safety run-in stage of approximately 12 pts, followed by a randomized stage in which approximately 100 pts will be randomly assigned in a 1:1 ratio to receive either cobi + paclitaxel or placebo + paclitaxel. Pts will receive paclitaxel 80 mg/m2 on Days 1, 8, and 15 of each 28-day cycle and cobi/placebo 60 mg/day on Days 3-23 of each 28-day cycle until progression of disease or toxicity occurs.

Key eligibility criteria:

• Metastatic or locally advanced (not amenable to curative resection) TNBC

• No prior systemic therapy for metastatic or unresectable locally advanced TNBC

• Neoadjuvant or adjuvant chemotherapy or radiation therapy is allowed if completed >6 months before the start of study treatment

• Measureable disease using Response Evaluation Criteria In Solid Tumors, version 1.1 (RECIST v1.1)

• History of or active untreated or unstable brain metastases or requiring corticosteroids for brain metastases precludes eligibility

• Left ventricular ejection fraction (LVEF) greater than the institutional lower limit of normal or above 50%

Specific aims of the safety run-in stage: Determine the safety and tolerability of cobi when administered in combination with paclitaxel.

Specific aims of the randomized stage: Investigator-assessed PFS (primary end point); safety; pharmacokinetics; the effect of intrinsic subtypes and genetic alterations in PFS; mechanisms of resistance; and health-related quality of life.

Accrual: Approximately 112 pts from sites across Europe, North America, and the Asia-Pacific region.

Statistical methods: In the randomized stage, pts will be followed up until a total of 60 PFS events occur across the 2 arms. This provides 77% power to detect a hazard ratio of 0.5 at a two-sided significance level of 0.05.

Contact information: Registered with ClinicalTrials.gov, identifier NCT02322814. For more information, please contact Roche/Genentech trials, 888-662-6728 (US only) or reference study ID WO29479 at www.roche.com/about_roche/roche_worldwide.htm.

Citation Format: Kim S-B, Miles D, Rhee J, Yan Y, Hsu J, Brufsky A. COLET: A multistage, phase 2 study evaluating the safety and efficacy of cobimetinib in combination with paclitaxel as first-line treatment for patients with metastatic triple-negative breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT1-03-18.