Abstract P4-05-02: Impact of hormone receptor status on clinicopathological characteristics and outcomes among HER2-positive metastatic breast cancer patients in the ESME database

Introduction. Evidence suggests that human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer (MBC) patients have different clinical characteristics and outcomes according to the hormone receptor (HR) status. We aimed to evaluate the impact of HR status in this population extracted from a large real-world database. Methods. We performed a retrospective analysis of HER2+ MBC patients (pts) included in the real world ESME MBC database (NCT03275311) between 2008 and 2017. Descriptive statistics, the Kaplan-Meier method and Cox proportional hazards models were used to report characteristics, outcomes and prognostic factors. Results. Of 4,145 HER2+ MBC pts eligible for our analysis, 1,449 (35%) had HR-negative (HR-), while 2,696 (65%) had HR-positive (HR+) tumors. Pts with HR- tumors had metastases earlier (median 9.3 vs 28.0 mo from primary cancer), had more often de novo MBC (47.6% vs 38.1%), grade III tumors (50.9% vs 33.6%), visceral metastases (70.9% vs 60.8%) and less often bone only disease (8.4% vs 21.1%) compared to those with HR+ tumors, all p<0.001. Pts with HR+ MBC received less frequently an anti-HER2+ targeted therapy during first line of treatment than pts with HR- tumors (74.9% vs 90.8%, p<0.001). Pts with HR- MBC had significantly worse outcomes than those with HER2+/HR+ MBC, with median overall survival (OS) 42.0 mo [95% CI 38.8-45.2] vs 55.9 mo [95% CI 53.7-59.4], p<0.001, and median progression-free survival (PFS) 9.8 mo [95%CI 9.2-11] vs 12.2 mo [95%CI 11.5-12.9], p=0.012, respectively. The independent prognostic value of HR status was confirmed in a multivariable analysis for OS (HR- versus HR+, hazard ratio=1.25 [1.13-1.39], p<0.001) but not for PFS (hazard ratio=1.03 [95%CI 0.95-1.13], p=0.8) (Table 1 for OS). The multivariable analysis also included tumor grade, age at and time to MBC diagnosis, presence of visceral metastases, number of metastatic sites and performance status as prognostic factors. In the HR+ population, ER and PR statuses were not prognostic. Conclusions. These data confirm the remaining strong and independent adverse prognostic effect of negative hormone receptors among pts with HER2+ MBC treated in the past 12 years.

Cox multivariable model for overall survival in patients with HER2-positive MBCCategoriesNHazard ratio95% CIp valueTumor gradeGrade I/II17711<0.001Grade III15741.13[1.03-1.25]NA5811.15[1.01-1.31]ER/PR statusER+/PR+14571<0.001ER+/PR-9711.03[0.92-1.16]ER-/PR+1021.03[0.77-1.36]ER-/PR-13961.25[1.13-1.39]Age at MBC diagnosis<55 years17561<0.001≥55 years21701.26[1.16-1.38]Time to MBC diagnosis<6 months16351<0.0016-24 months5082.53[2.22-2.89]24-60 months8721.75[1.56-1.96]≥60 months9111.19[1.06-1.35]Visceral metastasesNo14061<0.001Yes25201.54[1.38-1.71]No of metastatic sites<330911<0.001≥38351.65[1.48-1.84]ECOG PSPS 010101<0.001PS 18021.62[1.4-1.87]PS 2-43923.34[2.83-3.95]NA17222.34[2.07-2.64]

Citation Format: Luc Cabel, Matthieu Carton, Veronique Dieras, Thierry Petit, Severine Guiu, Corinne Veyret, Anthony Goncalves, Lionel Uwer, Paule Augereau, Jean-Marc Ferrero, Christelle Levy, Florence Dalenc, Isabelle Desmoulins, Marie Ange Mouret-Reynier, Marc Debled, Thomas Bachelot, Jean-Christophe Eymard, Barbara Pistilli, Jean Sebastien Frenel, Michael Chevrot, Audrey Mailliez, Marcela Carausu. Impact of hormone receptor status on clinicopathological characteristics and outcomes among HER2-positive metastatic breast cancer patients in the ESME database [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 P4-05-02.

De novo metastatic breast cancer in patients with a small locoregional tumour (T1-T2/N0): Characteristics and prognosis

INTRODUCTION

The estimated rate of de novo metastatic breast cancer (dnMBC) at the time of diagnosis is between 5 to 12%. International guidelines recommend metastatic work-up (MWU) only in women with advanced breast cancer. The purpose of this study was to describe the characteristics and prognosis of patients with dnMBC diagnosed without an initial indication for MWU.

METHODS

We conducted a retrospective, comparative study in dnMBC patients selected from the ESME-MBC cohort. Patients were treated in France between 2008 and 2016. We compared two populations: patients in whom dnMBC was diagnosed by staging although not indicated by guidelines (non-guideline staging [NGS]) and those in whom dnMBC was diagnosed by guideline staging (GS).

RESULTS

During the study period, 22,463 patients with MBC were included in the ESME cohort. Among them, 6698 were dnMBC patients. In 247 of these patients (6% of dnMBC and 1% of the overall population), dnMBC was diagnosed by non-guideline staging. Women in this group were significantly younger (57 vs. 59 years, p = 0.02) and had fewer metastatic sites at diagnosis than dnMBC-GS patients. The two groups were not significantly different in terms of the other characteristics. Overall survival (OS) and progression-free survival (PFS) were better in the dnMBC-NGS group than in the dnMBC-GS group. The impact on survival was confirmed by univariate and multivariate analysis (HR 1.83 [1.31-2.57], p < 0.01).

CONCLUSION

This study provides the first description of a very specific population. These patients with dnMBC-NGS were younger and more likely to have oligometastatic disease with a better prognosis.

Outcomes in patients (pts) aged ≥65 years in the phase 3 ASCENT study of sacituzumab govitecan (SG) in metastatic triple-negative breast cancer (mTNBC)

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Background: Approximately 20% of pts diagnosed with TNBC are aged ≥65 y. Often, older pts are less fit for chemotherapy due to a greater rate of comorbidities, increased use of medications, and pre-existing frailty or functional loss. SG is an antibody-drug conjugate composed of an anti–Trop-2 antibody coupled to the cytotoxic SN-38 payload via a proprietary, hydrolyzable linker. The landmark phase 3 ASCENT study (NCT02574455) showed improved outcomes with SG vs single-agent chemotherapy of physician’s choice (TPC) in pts with relapsed/refractory mTNBC (median progression-free survival [PFS], 5.6 vs 1.7 mo; median overall survival [OS], 12.1 vs 6.7 mo). Here we assess the impact of age on the efficacy and safety of SG in ASCENT. Methods: Pts with mTNBC refractory/relapsing after ≥2 prior chemotherapies were randomized 1:1 to receive SG (10 mg/kg IV on days 1 and 8, every 21 days) or TPC (capecitabine, eribulin, vinorelbine, or gemcitabine) until disease progression/unacceptable toxicity. Primary endpoint was PFS per RECIST 1.1 by independent review in brain metastases-negative (BMNeg) pts. Safety outcomes were assessed in all treated pts. This prespecified subgroup analysis assessed the impact of age (pts ≥65 y) on PFS, OS, and safety. Results: Of 529 pts enrolled, 468 were BMNeg (median age, 54 y); of these, 44/235 pts (19%) who received SG and 46/233 pts (20%) who received TPC were aged ≥65 y. SG treatment improved median PFS vs TPC in pts ≥65 y (7.1 vs 2.4 mo; HR, 0.22; 95% CI, 0.12-0.40). SG vs TPC treatment also improved median OS in pts ≥65 y (15.3 vs 8.2 mo; HR, 0.37; 95% CI, 0.22-0.64). Treatment with SG vs TPC resulted in higher ORR (50% vs 0%) and clinical benefit rate (CBR, 61% vs 9%) in pts ≥65 y. Of the 7 pts ≥75 y who received SG, 2 had partial response, 4 had stable disease [SD], and 1 had SD > 6 mo as best response. In pts < 65 y, median PFS for SG vs TPC was 4.6 vs 1.7 mo (HR, 0.46; 95% CI, 0.35-0.59), and median OS was 11.2 vs 6.6 mo (HR, 0.50; 95% CI, 0.40-0.64), respectively; the ORR and CBR were 31% vs 6% and 41% vs 9%, respectively. Pts ≥65 y treated with SG vs TPC had similar rates of all grade and grade ≥3 treatment-emergent adverse events (TEAEs). TEAEs leading to dose reduction were similar in pts ≥65 y in the SG vs TPC arms (35% vs 33%) and were lower in pts < 65 y (19% vs 24%). Key treatment-related TEAEs leading to dose reduction in pts ≥65 y in the SG vs TPC arms were neutropenia (including febrile neutropenia; 14% vs 25%), fatigue (10% vs 4%), diarrhea (6% vs 0%), and nausea (4% vs 0%). TEAEs leading to treatment discontinuation with SG vs TPC were low in pts ≥65 y (2% vs 2%) and < 65 y (5% vs 6%). There were no treatment-related AEs leading to death in any SG-treated age group. Conclusions: Irrespective of age, pts who received SG had a significant survival benefit vs TPC, with a tolerable safety profile. Proactive AE monitoring and management will allow optimal therapeutic exposure to SG in older pts. Clinical trial information: NCT02574455 .

The tumor microenvironment (TME) and atezolizumab + nab-paclitaxel (A+nP) activity in metastatic triple-negative breast cancer (mTNBC): IMpassion130

1006

Background: IMpassion130 was the first randomized phase 3 study to show clinical benefit of cancer immunotherapy (CIT) in untreated PD-L1+ mTNBC. Enhanced A + nP efficacy vs placebo (P) + nP was seen in pts with a richer immune TME but was confined to PD-L1 IC+ pts (PD-L1–expressing immune cells on ≥1% of tumor area; Emens JNCI 2021). While TNBC molecular subtyping and CD8 localization are prognostic in early TNBC, it is unknown whether these features are associated with CIT benefit in mTNBC. This exploratory analysis aimed to identify TME components associated with A + nP efficacy in IMpassion130. Methods: IHC was used to assess PD-L1 status (VENTANA SP142) and immune phenotypes (inflamed/excluded/desert per CD8 stromal/intratumoral localization; Mariathasan Nature 2018). RNA-seq was used for molecular subtyping (Burstein CCR 2015) and pathway analyses (MSigDB Hallmark). Cox regression was used to compare PFS/OS between A + nP vs P + nP, adjusted for prior taxanes, liver mets. Results: Sample classification and PD-L1 distribution are shown (Table). Improved PFS with A + nP vs P + nP was seen in PD-L1 IC+ inflamed and excluded tumors, but improved OS was limited to PD-L1 IC+ inflamed tumors. PD-L1 IC+ basal-like immune activated (BLIA) and immune suppressed (BLIS) subgroups derived PFS benefit, but OS benefit was limited to PD-L1 IC+ BLIA subgroups. In PD-L1 IC+ pts, pathway analysis identified proliferation/DNA damage repair (basal-like tumor features) and angiogenesis/ER response (higher in luminal androgen receptor [LAR]/ mesenchymal [MES] tumors) were associated with improved and reduced PFS, respectively. Conclusions: PD-L1 IC+ immune-inflamed tumors and PD-L1 IC+ BLIA tumors show highest CIT sensitivity, and LAR tumors may be resistant to CIT. These data warrant further study and validation. Clinical trial information: NCT02425891 .[Table: see text]

Assessment of sacituzumab govitecan (SG) in patients with prior neoadjuvant/adjuvant chemotherapy in the phase 3 ASCENT study in metastatic triple-negative breast cancer (mTNBC)

1080

Background: mTNBC is a heterogenous disease with few treatment options and poor outcomes. Pts who recur ≤ 12 mo after completing (neo)adjuvant chemotherapy may represent a subset with more aggressive disease. SG is an antibody-drug conjugate composed of an anti–Trop-2 antibody coupled to the cytotoxic SN-38 payload via a proprietary, hydrolyzable linker. SG received accelerated approval for pts with mTNBC who received ≥ 2 prior therapies for metastatic disease; clinical benefit for SG over treatment of physician's choice (TPC) was confirmed in the phase 3 ASCENT study (NCT02574455) for median progression-free survival (PFS; 5.6 vs 1.7 mo), median overall survival (OS; 12.1 vs 6.7 mo), objective response rate (ORR; 35% vs 5%), clinical benefit rate (CBR; 45% vs 9%), and median duration of response (6.3 vs 3.6 mo). This ASCENT subanalysis of pts with mTNBC who recurred ≤ 12 mo after (neo)adjuvant chemotherapy and then only received 1 line of therapy in the metastatic setting assessed the benefit of SG in this subgroup vs the overall trial population. Methods: In ASCENT, pts with mTNBC refractory/relapsing after ≥ 2 prior chemotherapies were randomized 1:1 to receive SG (10 mg/kg IV on days 1 and 8, every 21 days) or TPC (capecitabine, eribulin, vinorelbine, or gemcitabine). Per protocol, a pt was eligible after only 1 prior regimen in the metastatic setting if their disease recurred within 12 months of completing (neo)adjuvant therapy. Primary endpoint was PFS per RECIST 1.1 by independent review in brain metastases-negative (BMNeg) pts. Efficacy and safety was assessed in a subset of pts who recurred ≤ 12 mo after (neo)adjuvant chemotherapy and then received 1 line of therapy in the metastatic setting. Results: In total, 33 and 32 BMNeg pts with a median age of 49 and 51 yrs received SG and TPC in this subgroup, respectively. In this subgroup, treatment with SG (vs TPC) improved PFS (median 5.7 vs 1.5 mo; HR, 0.41; 95% CI, 0.22-0.76; P = 0.0049) and OS (median 10.9 vs 4.9 mo; HR, 0.51; 95% CI, 0.28-0.91; P = 0.0227). We also observed higher ORR (30% vs 3%) and CBR (42% vs 6%) with a median response duration of 6.7 mo with SG vs not calculable with TPC. The efficacy results from this subgroup are similar to those for SG vs TPC in the overall BMNeg population. The safety profile of SG in pts in this subgroup was consistent with prior reports. There were no treatment-related deaths with SG. Conclusions: Pts with mTNBC who recurred ≤ 12 mo after (neo)adjuvant therapy and then had 1 line of prior therapy in the metastatic setting may represent a subset with more aggressive disease. In this subgroup, pts had superior outcomes with SG vs TPC in the second-line metastatic setting, consistent with the benefit seen in the overall BMNeg population. Studies are ongoing (NeoSTAR, NCT04230109; SASCIA, NCT04595565) to evaluate SG as an earlier-line treatment option for TNBC. Clinical trial information: NCT02574455 .

persevERA Breast Cancer (BC): Phase III study evaluating the efficacy and safety of giredestrant (GDC-9545) + palbociclib versus letrozole + palbociclib in patients (pts) with estrogen-receptor-positive, HER2-negative locally advanced or metastatic BC (ER+/HER2– LA/mBC)

TPS1103

Background: Modulating estrogen synthesis and/or ER activity is the mainstay of treatment for pts with ER+ BC. Despite substantial progress, many pts experience relapse during/after adjuvant endocrine therapy. However, even though resistant to aromatase inhibitors (AIs) or tamoxifen, growth and survival of the majority of tumors are thought to remain dependent on ER signaling. Therefore, pts with ER+ BC can still respond to second- or third-line endocrine treatment after progression on prior therapy (Di Leo 2010; Baselga 2012). Therapeutic resistance can arise from mutations in ESR1, which can drive estrogen-independent transcription and proliferation. The highly potent, non-steroidal oral selective ER degrader giredestrant achieves robust ER occupancy and is active regardless of ESR1 mutation status. Phase I data indicate that giredestrant is well tolerated, with encouraging activity as a single agent and in combination with the CDK4/6 inhibitor palbociclib (Lim 2020). Single-agent activity was observed after prior treatment with fulvestrant and/or a CDK4/6 inhibitor (Jhaveri 2019). Methods: persevERA BC (NCT04546009) is a double-blind, placebo-controlled, randomized, multicenter phase III study designed to evaluate the efficacy and safety of first-line giredestrant + palbociclib in pts with ER+/HER2– LA/mBC. Randomization: 1:1 to either giredestrant (30 mg PO) plus letrozole placebo QD or letrozole (2.5 mg PO) plus giredestrant placebo QD on Days 1–28 of each 28-day cycle, with palbociclib (125 mg PO QD) on Days 1–21 of each 28-day cycle. Men and premenopausal women will receive an LHRH agonist. Eligibility: females or males ≥18 years old with measurable disease or evaluable bone disease and no prior treatment for advanced disease. Pts who received prior fulvestrant or who have relapsed within 12 months of completion of (neo)adjuvant therapy with an AI and/or prior therapy with CDK4/6 inhibitor are not eligible; relapse during tamoxifen therapy but > 24 months after the start of tamoxifen therapy is allowed. Stratification: site of disease, disease-free interval since the end of (neo)adjuvant therapy, menopausal status, and geographic region. Primary efficacy endpoint: progression-free survival (determined locally by the investigator per RECIST v1.1). Secondary endpoints include overall survival, objective response rate, duration of response, clinical benefit rate, QoL, and safety. Enrollment is open (first patient in: Oct 9, 2020); target recruitment is 978 pts across all sites in a global enrollment phase. After completion of the global enrollment, additional pts may be enrolled in China. Clinical trial information: NCT04546009 .

Abstract GS4-01: Results from CONTESSA: A phase 3 study of tesetaxel plus a reduced dose of capecitabine versus capecitabine alone in patients with HER2-, hormone receptor + (HR+) metastatic breast cancer (MBC) who have previously received a taxane

Objectives: The key objectives of CONTESSA are to evaluate the efficacy and safety of tesetaxel plus a reduced dose of capecitabine as an all-oral regimen versus capecitabine alone in patients with HER2-, HR+ MBC previously treated with a taxane.

Rationale: Tesetaxel is a novel, oral taxane with several properties that make it unique, including: oral administration with a low pill burden; a long (8-day) terminal plasma half-life in humans, enabling infrequent, once-every-3 weeks (Q3W) dosing; no observed hypersensitivity reactions; and significant activity against chemotherapy-resistant breast cancer cell lines. More than 1,000 patients have been treated with tesetaxel in clinical studies. Tesetaxel had encouraging monotherapy activity in a Phase 2 study in 38 patients with HER2-, HR+ MBC, with a confirmed objective response rate (ORR) per RECIST 1.1 of 45% and median progression-free survival (PFS) of 5.4 months (Seidman et al, 2018 ASCO Annual Meeting).

Methodology: CONTESSA is a multinational, multicenter, randomized (1:1), Phase 3 registration study comparing tesetaxel (27 mg/m2 on Day 1 of a 21-day cycle) plus a reduced dose of capecitabine (1,650 mg/m2/day on Days 1-14 of a 21-day cycle) to the approved dose of capecitabine alone (2,500 mg/m2/day on Days 1-14 of a 21-day cycle) in patients with HER2-, HR+ MBC who have received no more than one chemotherapy regimen for advanced disease and have received a taxane in the (neo)adjuvant setting. There was no restriction on the disease-free interval following taxane therapy. The primary endpoint is PFS assessed by an Independent Radiologic Review Committee (IRC). CONTESSA was designed with 90% power to detect a 2.5-month improvement in median PFS (HR=0.71). Secondary endpoints are overall survival (OS), ORR and disease control rate.

Results: CONTESSA, which enrolled 685 patients, met the primary endpoint of improved PFS as assessed by the IRC. Median PFS was 9.8 months for tesetaxel plus a reduced dose of capecitabine versus 6.9 months for capecitabine alone, an improvement of 2.9 months [HR=0.716 (95% CI: 0.573-0.895); p=0.003]. ORR was 57% for tesetaxel plus a reduced dose of capecitabine versus 41% for capecitabine alone (p=0.0002). OS data are immature. Tesetaxel plus capecitabine was associated with a manageable side effect profile consistent with previous clinical studies. Grade ≥3 treatment-emergent adverse events (TEAEs) that occurred in ≥5% of patients (tesetaxel plus capecitabine vs. capecitabine alone) were: neutropenia (71.2% vs. 8.3%); diarrhea (13.4% vs. 8.9%); hand-foot syndrome (6.8% vs. 12.2%); febrile neutropenia (12.8% vs. 1.2%); fatigue (8.6% vs. 4.5%); hypokalemia (8.6% vs. 2.7%); leukopenia (10.1% vs. 0.9%); and anemia (8.0% vs. 2.1%). TEAEs resulting in treatment discontinuation in ≥1% of patients (tesetaxel plus capecitabine vs. capecitabine alone) were: neutropenia or febrile neutropenia (4.2% vs. 1.5%); neuropathy (3.6% vs. 0.3%); diarrhea (0.9% vs. 1.5%); and hand-foot syndrome (0.6% vs. 2.1%). Treatment discontinuation due to any adverse event occurred in 23.1% of patients treated with tesetaxel plus capecitabine versus 11.9% of patients treated with capecitabine alone. Grade 2 alopecia occurred in 8.0% of patients treated with tesetaxel plus capecitabine versus 0.3% of patients treated with capecitabine alone. Grade ≥3 neuropathy occurred in 5.9% of patients treated with tesetaxel plus capecitabine versus 0.9% of patients treated with capecitabine alone.

Conclusion: An all-oral regimen of tesetaxel plus a reduced dose of capecitabine significantly improved PFS versus capecitabine alone. Neutropenia was the most frequent Grade ≥3 TEAE. Rates of clinically significant alopecia and neuropathy were low.

Citation Format: Joyce O'Shaughnessy, Lee Schwartzberg, Martine Piccart, Hope S. Rugo, Denise A Yardley, Javier Cortes, Michael Untch, Nadia Harbeck, Gail S. Wright, Igor Bondarenko, John Glaspy, Zbigniew Nowecki, Fadi Kayali, Arlene Chan, Christelle Levy, Mei-Ching Liu, Sung-Bae Kim, Julie Lemieux, Alexey Manikhas, Sara Tolaney, Elaine Lim, Andrea Gombos, Agostina Stradella, Mark Pegram, Peter Fasching, Laszlo Mangel, Vladimir Semiglazov, Veronique Dieras, Luca Gianni, Michael A Danso, Jeff Vacirca, Stew Kroll, Joseph O'Connell, Kevin Tang, Thomas Wei, Andrew Seidman. Results from CONTESSA: A phase 3 study of tesetaxel plus a reduced dose of capecitabine versus capecitabine alone in patients with HER2-, hormone receptor + (HR+) metastatic breast cancer (MBC) who have previously received a taxane [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 GS4-01.

Real-world survival outcomes of heavily pretreated patients with refractory HR+, HER2-metastatic breast cancer receiving single-agent chemotherapy-a comparison with MONARCH 1

PURPOSE

In MONARCH 1 (NCT02102490), single-agent abemaciclib demonstrated promising efficacy activity and tolerability in a population of heavily pretreated women with refractory HR+, HER2- metastatic breast cancer (MBC). To help interpret these results and put in clinical context, we compared overall survival (OS) and duration of therapy (DoT) between MONARCH 1 and a real-world single-agent chemotherapy cohort.

METHODS

The real-world chemotherapy cohort was created from a Flatiron Health electronic health records-derived database based on key eligibility criteria from MONARCH 1. The chemotherapies included in the cohort were single-agent capecitabine, gemcitabine, eribulin, or vinorelbine. Results were adjusted for baseline demographics and clinical differences using Mahalanobis distance matching (primary analysis) and entropy balancing (sensitivity analysis). OS and DoT were analyzed using the Kaplan-Meier method and Cox proportional hazards regression.

RESULTS

A real-world single-agent chemotherapy cohort (n = 281) with eligibility criteria similar to the MONARCH 1 population (n = 132) was identified. The MONARCH 1 (n = 108) cohort was matched to the real-world chemotherapy cohort (n = 108). Median OS was 22.3 months in the abemaciclib arm versus 13.6 months in the matched real-world chemotherapy cohort with an estimated hazard ratio (HR) of 0.54. The median DoT was 4.1 months in MONARCH 1 compared to 2.9 months in the real-world chemotherapy cohort with HR of 0.76.

CONCLUSIONS

This study demonstrates an approach to create a real-world chemotherapy cohort suitable to serve as a comparator for trial data. These exploratory results suggest a survival advantage and place the benefit of abemaciclib monotherapy in clinical context.

Clinical outcome of patients experiencing central nervous system progression on first-line pertuzumab and trastuzumab for HER2-positive metastatic breast cancer in a real-life cohort

2527

Background: Isolated central nervous system (CNS) progression on first-line systemic therapy with Trastuzumab (T) and Pertuzumab (P) for HER2-positive metastatic breast cancer (MBC) is a therapeutic challenge. Our aim was to describe the clinical outcome and current treatment strategies for such patients in a large retrospective cohort. Methods: Patients (pts) were selected among all MBC pts included in the French Epidemiological Strategy and Medical Economics (ESME) database involving 18 specialized cancer centers (NCT03275311). CNS progression-free survival (CNS-PFS), progression-free survival (PFS) and overall survival (OS) from diagnostic of brain metastases (BM) were estimated using the Kaplan-Meier method. Results: Between January 2008 and December 2016, 995 pts were treated with first-line T and P for their HER2-positive MBC. They were 55 years old in median, with tumors expressing hormone-receptors in 62%. A total of 132 pts (13%) experienced isolated CNS progression on T and P, with a median time from metastatic diagnosis to CNS progression of 12 months. It was the first CNS progression for 108 pts (82%) while 24 (18%) already had BM at time of metastatic relapse. After CNS progression, T and P were continued for 58% of pts (n = 73). The remaining 47 pts were switched to another HER2-directed therapy (T-DM1 for 57%, T alone or combined with chemotherapy for 36% and lapatinib for 21%). Among those 132 pts, 37% received whole-brain radiotherapy, 18% stereotactic radiation therapy, and 11% surgery. Systemic treatment was combined with CNS-directed therapy for 50% of pts. Median follow-up is 21 months (95%CI: 14.9-25.5) from the diagnosis of CNS metastases. Median OS (mOS) of the 132 pts is 35 months (95%CI: 29.2-53,6), and median PFS 7 months (95%CI: 6.3- 9.2). A total of 77 pts (58.3%) experienced a new CNS progression with a median CNS-PFS of 9 months (95%CI: 7.6-12,0). Patient who stayed on T and P had a significantly better OS in comparison to pts who were switched to another systemic HER2-directed therapy (mOS not evaluable vs23 months), whereas PFS and CNS-PFS were similar between groups. Conclusions: In this real life setting, isolated CNS progression occurred among 13% of pts with HER2+ MBC on first-line treatment with T and P, after a median time of 12 months. Following current ASCO recommendations, continuation of T and P after CNS-directed therapy, seemed to be adequate. Nevertheless, time to subsequent progression is short and better therapeutic options are needed.

Veliparib (V) monotherapy after progression on placebo (PL) + carboplatin/paclitaxel (CP) in patients with advanced HER2-negative gBRCA-associated breast cancer: Crossover outcomes and exploratory biomarker analyses in BROCADE3

1097

Background: In BROCADE3 (NCT02163694), addition of the PARP inhibitor (PARPi) V to CP improved PFS in patients (pts) with g BRCA-associated advanced breast cancer (hazard ratio 0.71 [95% CI 0.57–0.88], p = 0.002). Reversion mutations may account for resistance to platinum-based CT and PARPi. Efficacy, safety, and exploratory biomarker analyses for pts randomized to PL + CP who received crossover (Cx) V monotherapy after progression are reported. Methods: 513 total pts were randomized 2:1 to V + CP or PL + CP. V/PL, C, and P could be discontinued independently prior to progression, leading to varying platinum-free intervals at the time of progression. After progression, pts in the PL + CP arm could receive open-label Cx V monotherapy (300–400 mg BID continuous), beginning within 60 d of progression and continuing to second progression. Adverse events (AEs) and activity during Cx V were assessed. Exploratory analysis of BRCA reversion mutations restoring BRCA1/2 protein function that emerged during PL + CP treatment was performed on plasma circulating tumor DNA using targeted-amplicon next generation sequencing. Results: At data cutoff, 75 pts initially randomized to PL + CP had ≥1 dose of Cx V. Mean (range) duration of Cx V was 154 d (2–966). Activity during Cx V is in the Table. Mean (range) platinum-free interval at time of first dose of Cx V was 3.1 mos (0.4–10.9) vs 8.1 mos (1.0–34.9) in pts who had progressed vs had not progressed by 24 wks after first dose of Cx V. BRCA reversion analysis was completed for 18 Cx pts. Reversion mutations were identified in 1/18 pts (5.6%). This patient had Cx V duration of 19 d and had progressed by 24 wks. BRCA reversion analysis on additional Cx pts will be presented. Most common AEs during Cx V were nausea (61%), vomiting (29%), fatigue (24%), and diarrhea (21%). Any grade anemia, neutropenia, and thrombocytopenia occurred in 7%, 15%, and 7% of pts. Three pts (4%) experienced a convulsion event. Conclusions: Platinum-free interval may influence efficacy of subsequent PARPi. Impact of BRCA reversion mutations warrants further evaluation. Cross-resistance may limit PARPi efficacy after platinum failure. Clinical trial information: NCT02163694 . [Table: see text]

Veliparib (V) monotherapy (monoTx) following combination therapy with V + carboplatin/paclitaxel (CP) in patients with gBRCA-associated advanced breast cancer: Exploratory results from BROCADE3

1091

Background: In BROCADE3 (NCT02163694), addition of PARP inhibitor V to CP resulted in improved progression-free survival (PFS) (HR 0.71 [95% CI 0.57−0.88], p=0.002) in patients (pts) with advanced HER2-negative breast cancer and g BRCA1/2 mutation. A subset of pts transitioned to V/placebo (PL) monoTx at an intensified dose/schedule after CP discontinuation prior to progression (investigator discretion). Here, we evaluate the impact of this transition on efficacy and safety. Methods: Pts were randomized 2:1 to CP with V (n=337) or PL (n=172). V (120 mg po BID) or PL was given on Days (D) −2 to 5, C (AUC 6) on D1, and P (80 mg/m2) on D1, 8, and 15 (21-day cycles). Pts who transitioned to monoTx received V/PL 300-400mg BID daily until progression. A Cox model with a time varying covariate indicating transition from V/PL with CP to V/PL monoTx was fit to estimate treatment effect during combination and monoTx phases. PFS by cycles of CP prior to monoTx and AEs during monoTx are summarized. Results: A subgroup of 136 (40%) and 58 (34%) pts on the V and PL arms, respectively, received monoTx. When a Cox model with a time-varying covariate was fit for PFS (per investigator), the nominal P-value for treatment by covariate interaction was 0.038. The HRs (95% CI) for V vs PL during combination therapy and monoTx were 0.81 (0.62–1.06) and 0.49 (0.33–0.73). The Table summarizes PFS by cycles of C and/or P prior to monoTx. Common AEs (>20% of pts) during V or PL monoTx were nausea (52%/10%), fatigue (23%/12%), headache (21%/17%), and diarrhea (21%/9%). Seizures (2.2%/0%) were reported during monoTx. Rates of cytopenias for V or PL monoTx were: anemia 12%/14%; neutropenia 13%/12%; and thrombocytopenia 10%/5%. Conclusions: These analyses suggest that pts treated with V + CP derive benefit from both combination therapy as well as V monoTx after CP discontinuation. Pts receiving V monoTx after ≤ 6 cycles of VCP experienced a similar benefit to those who transitioned to monoTx after 7–12 cycles of VCP, suggesting that V maintenance therapy may be suitable following a limited duration of combination therapy. Clinical trial information: NCT02163694 . [Table: see text]

Contemporary outcomes of metastatic breast cancer among 22,000 women from the multicentre ESME cohort 2008-2016

AIM

Real-world data inform the outcome comparisons and help the development of new therapeutic strategies. To this end, we aimed to describe the full characteristics and outcomes in the Epidemiological Strategy and Medical Economics (ESME) cohort, a large national contemporary observational database of patients with metastatic breast cancer (MBC).

METHODS

Women aged ≥18 years with newly diagnosed MBC and who initiated MBC treatment between January 2008 and December 2016 in one of the 18 French Comprehensive Cancer Centers (N = 22,109) were included. We assessed the full patients' characteristics, first-line treatments, overall survival (OS) and first-line progression-free survival, as well as updated prognostic factors in the whole cohort and among the 3 major subtypes: hormone receptor positive and HER2-negative (HR+/HER2-, n = 13,656), HER2-positive (HER2+, n = 4017) and triple-negative (n = 2963) tumours.

RESULTS

The median OS of the whole cohort was 39.5 months (95% confidence interval [CI], 38.7-40.3). Five-year OS was 33.8%. OS differed significantly between the 3 subtypes (p < 0.0001) with a median OS of 43.3 (95% CI, 42.5-44.5) in HR+/HER2-; 50.1 (95% CI, 47.6-53.1) in HER2+; and 14.8 months (95% CI, 14.1-15.5) in triple-negative subgroups, respectively. Beyond performance status, the following variables had a constant significant negative prognostic impact on OS in the whole cohort and among subtypes: older age at diagnosis of metastases (except for the triple-negative subtype), metastasis-free interval between 6 and 24 months, presence of visceral metastases and number of metastatic sites ≥ 3.

CONCLUSIONS

The ESME program represents a unique large-scale real-life cohort on MBC. This study highlights important situations of high medical need within MBC patients. DATABASE REGISTRATION: clinicaltrials.gov Identifier NCT032753.

Actionability of HER2-amplified circulating tumor cells in HER2-negative metastatic breast cancer: the CirCe T-DM1 trial

BACKGROUND

In this prospective phase 2 trial, we assessed the efficacy of trastuzumab-emtansine (T-DM1) in HER2-negative metastatic breast cancer (MBC) patients with HER2-positive CTC.

METHODS

Main inclusion criteria for screening were as follows: women with HER2-negative MBC treated with ≥ 2 prior lines of chemotherapy and measurable disease. CTC with a HER2/CEP17 ratio of ≥ 2.2 by fluorescent in situ hybridization (CellSearch) were considered to be HER2-amplified (HER2_amp). Patients with ≥ 1 HER2_amp CTC were eligible for the treatment phase (T-DM1 monotherapy). The primary endpoint was the overall response rate.

RESULTS

In 154 screened patients, ≥ 1 and ≥ 5 CTC/7.5 ml of blood were detected in N = 118 (78.7%) and N = 86 (57.3%) patients, respectively. ≥1 HER2_amp CTC was found in 14 patients (9.1% of patients with ≥ 1 CTC/7.5 ml). Among 11 patients treated with T-DM1, one achieved a confirmed partial response. Four patients had a stable disease as best response. Median PFS was 4.8 months while median OS was 9.5 months.

CONCLUSIONS

CTC with HER2 amplification can be detected in a limited subset of HER2-negative MBC patients. Treatment with T-DM1 achieved a partial response in only one patient.

TRIAL REGISTRATION

NCT01975142, Registered 03 November 2013.

Abstract CT140: Circulating tumor cells as a tool to guide first line therapy in metastatic breast cancer: subgroup analyses of the STIC CTC Phase III utility trial

Background: Endocrine therapy (ET) is the preferred 1st line therapy in ER+ HER2- metastatic breast cancer (MBC) patients, but not all benefit from such strategy for which predictive biomarkers are lacking. Prior studies showed that circulating tumor cells (CTC) count is the strongest prognostic factor beyond PS in that population. The STIC CTC trial (NCT01710605) assessed whether CTC count could drive the choice between frontline ET or chemotherapy (CT, with or without ET maintenance).

Methods: For this multicenter phase 3 non-inferiority trial, main inclusion criteria were: ER+ HER2- MBC with no prior therapy, PS≤2, no contra-indication to ET or CT, informed consent. Patients were randomized 1:1 between clinically-driven choice (single agent ET if clinicallow, CT if clinicalhigh, as decided by physician based on clinical factors, blinded to CTC results) or a CTC-driven choice [ET if CTClow (&lt;5 CTCs/7.5mL), CT if CTChigh (≥5 CTCs/7.5mL)]. The primary objective was treatment efficacy ([PFS hazard ratio (HR)], non-inferiority being established if the upper bound of the PFS HR 2-sided 90%CI is &lt;1.25; secondary objectives included subgroup analyses (CTC status, patient characteristics) and OS.

Results: In this trial, 778 patients were randomized between both strategies. Of all patients, 71.0%, 26.6% and 2.4% were considered as endocrine-sensitive, with secondary or with primary endocrine resistance, respectively. In both arms (clinically- and CTC-driven), prognostic evaluation by physician/CTCs and allocated treatments were as follows: (i) clinicallow/CTClow 46.5% and 48.6% of patients, all treated with ET. (ii) clinicalhigh/CTChigh 14.0% and 13.0%, all treated with CT. (iii) clinicallow/CTChigh 26.1% and 24.2%, treated with ET or CT respectively. (iv) clinicalhigh/CTClow 13.4% and 14.0%, treated with CT or ET respectively. CTC-driven strategy met the primary endpoint, yielding a non-inferior PFS (median: 17 months; 95%CI [15.4-20.3] vs 18 months 95%CI[13.9-23.3]). In the 2 discordant subgroups, preplanned analyses showed the following results: in the clinicallow/CTChigh subgroup, patients treated with CT had a significantly longer PFS than those treated with ET (15.6 months, 95%CI [12.2-22.7] vs 10.5 months, 95%CI [7.3-15.4], log rank p=0.002). In the clinicalhigh/CTClow subgroup, patients treated with CT had a non-significant PFS advantage over patients treated with ET. Pooling these two subgroups of patients (N=292) with discordant treatment recommendations (depending on clinician or CTC count standpoint), an exploratory analysis showed that patients treated with CT frontline had significantly longer PFS (HR=0.66; 95%CI [0.51-0.85]) and OS (HR=0.65; 95%CI [0.43-0.98]); 2-year OS were 82.9% versus 74.7% in patients treated with CT (±maintenance ET) or ET, respectively.

Conclusion: This trial demonstrates the utility of CTC count to select 1st line therapy in ER+ HER2- MBC patients, especially in those for whom single agent ET is the recommended therapy based on clinical factors. With this modern prognostic biomarker, the STIC CTC trial is the first one to identify potential ER+ HER2- MBC patients who might derive more benefit from frontline CT followed by maintenance ET than from frontline ET, challenging current standards.

Funding: French Ministry of Health (PSTIC 2011); Menarini SB; Institut Curie.

Citation Format: Francois-Clement Bidard, William Jacot, Sylvain Dureau, Etienne Brain, Thomas Bachelot, Hugues Bourgeois, Anthony Goncalves, Sylvain Ladoire, Herve Naman, Florence Dalenc, Joseph Gligorov, Marc Espie, Christelle Levy, Jean-Marc Ferrero, Delphine Loirat, Paul Cottu, Veronique Dieras, Marie-Emmanuelle Legrier, Frederique Berger, Catherine Alix-Panabieres, Jean-Yves Pierga. Circulating tumor cells as a tool to guide first line therapy in metastatic breast cancer: subgroup analyses of the STIC CTC Phase III utility trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT140.

IMpassion130: updated overall survival (OS) from a global, randomized, double-blind, placebo-controlled, Phase III study of atezolizumab (atezo) + nab-paclitaxel (nP) in previously untreated locally advanced or metastatic triple-negative breast cancer (mTNBC)

1003

Background: IMpassion130 evaluated atezo (anti–PD-L1) + nP vs placebo + nP in 1L mTNBC. The primary PFS analysis found that atezo + nP significantly improved PFS in intent-to-treat (ITT) and PD-L1+ pts vs placebo + nP, with efficacy driven by the PD-L1+ population. At that time, the 1st interim OS analysis was conducted (Schmid, NEJM 2018). Here we report the 2nd interim OS analysis. Methods: Eligible pts had histologically documented locally advanced or mTNBC, ECOG PS 0-1 and tumor tissue for PD-L1 testing. Pts were randomized 1:1 to IV atezo 840 mg or placebo on d1 and d15 + nP 100 mg/m2 on d1, d8 and d15 of each 28-d cycle until progression (stratification factors: prior taxanes, liver metastases, PD-L1 on tumor-infiltrating immune cells [IC]). RECIST 1.1 PFS (in ITT and PD-L1+ pts) and OS (tested in ITT and, if significant, PD-L1+ pts) were co-primary endpoints. Results: OS data are shown (Table). As of data cutoff (Jan 2, 2019), 9% of pts in the atezo + nP arm and 3% in the placebo + nP arm were still on treatment. Statistical significance was not demonstrated in ITT pts, but a 7.0-month improvement in median OS was observed in PD-L1+ pts with atezo + nP (25.0 mo) vs placebo + nP (18.0 mo; HR, 0.71 [95% CI: 0.54, 0.93]). A 4.5-mo safety update (Schneeweiss, ASCO 2019, submitted) showed that atezo + nP remained tolerable. Conclusions: The 2nd IMpassion130 interim OS analysis was consistent with the 1st analysis, confirming clinically meaningful OS benefit with atezo + nP in previously untreated PD-L1+ mTNBC. Clinical trial information: NCT02425891. [Table: see text]

IMpassion130: Expanded safety analysis from a P3 study of atezolizumab (A) + nab-paclitaxel (nP) in patients (pts) with treatment (tx)-naïve, locally advanced or metastatic triple-negative breast cancer (mTNBC)

1068

Background: IMpassion130 showed PFS benefit with A + nP vs placebo (P) + nP as 1L tx for mTNBC in the ITT and PD-L1 IC+ pts. We report expanded safety data with 4.5-mo longer follow-up (FU), focusing on adverse events of special interest (AESI), potentially immune related. Methods: Pts with unresectable locally advanced or mTNBC received nP 100 mg/m2 IV (d1, 8 and 15 of a 28-d cycle) + A 840 mg IV q2w or P until PD or toxicity. Safety was a secondary endpoint. Results: With 15.6 mo of median FU, of 453 pts with A+nP and 437 pts with P+nP, 49% and 43% had Gr 3/4, 1% and <1% had Gr 5, 23% and 19% had serious AEs, and 58% and 42% had AESI, respectively. Most AESI (≥86%; either arm) were Gr 1/2. 14% (A+nP) vs 6% (P+nP) received systemic corticosteroids within 30 d of AESI onset. The only any-Gr AESI differing with A+nP vs P+nP were rash (34% vs 26%), hypo- (18% vs 5%) and hyperthyroidism (5% vs 1%) and pneumonitis (4% vs <1%). The leading cause of withdrawal was peripheral neuropathy, with Gr 3 affecting 6% (A+nP) vs 3% (P+nP). AESI median time to onset (TTO) was consistent with A monotherapy trials. Conclusions: A+nP had a tolerable safety profile, with no meaningful changes since the primary data cut. No cumulative toxicities or new or late-onset safety signals were seen with longer FU. Clinical trial information: NCT02425891. [Table: see text]

Patient-reported outcomes (PROs) from the phase III IMpassion130 trial of atezolizumab (atezo) plus nabpaclitaxel (nP) in metastatic triple-negative breast cancer (mTNBC)

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Background: In the IMpassion130 study in 1L mTNBC (N = 902), PFS with atezo + nP was significantly better than with placebo (P) + nP in ITT (HR, 0.80) and PD-L1 IC+ (HR, 0.62) patients (pts). Clinically meaningful OS improvement (HR, 0.62) was also seen in PD-L1+ pts. PROs were used to document pt perspectives on overall clinical benefit of atezo + nP. Methods: Pts received either atezo 840 mg or P q2w + nP 100 mg/m2 on days 1, 8 and 15 of each 28-day cycle until disease progression or intolerance. Pts completed the EORTC QLC-C30 and breast cancer module (QLQ-BR23) on day 1 of each cycle, at end of treatment (Tx) and q4w during follow-up for 1 y. Time to deterioration (TTD; first ≥ 10-point decrease from baseline [BL] held for 2 cycles) in HRQoL was a pre-defined secondary endpoint. Exploratory endpoints included TTD in function, and mean and mean change from BL scores (changes ≥ 10 considered clinically meaningful) in HRQoL, function and disease/Tx-related symptoms. Results: BL completion was 92% (QLQ-C30) and 89% (QLQ-BR23) and remained > 80% through Cycle 20 in both ITT and PD-L1 IC+ pts. No differences in median TTD in HRQoL (ITT: HR, 0.97 [95% CI: 0.80, 1.18]; PD-L1 IC+: HR, 0.94 [95% CI: 0.69, 1.28]), physical function (ITT: HR, 1.04 [95% CI: 0.86, 1.26]; PD-L1 IC+: HR, 1.02 [95% CI: 0.76, 1.37]) or role function (ITT: HR, 1.01 [95% CI: 0.83, 1.22]; PD-L1 IC+: HR, 0.77 [95% CI: 0.57, 1.04]) were observed between arms in either population. Mean scores at BL for HRQoL (ITT: 66.0 [atezo + nP] vs 64.3 [P + nP]; PD-L1 IC+: 67.5 vs 65.0), physical function (ITT: 80.4 vs 79.2; PD-L1 IC+: 82.8 vs 79.4) and role function (ITT: 72.7 vs 71.0; PD-L1 IC+: 73.7 vs 71.7) were similar between arms and throughout the course of Tx. In both arms, HRQoL, physical and role function, and Tx symptoms (fatigue, diarrhea, nausea, vomiting) were stable during Tx, with no clinically meaningful changes seen until pts discontinued Tx. Conclusions: PRO data suggest that atezo + nP was tolerable and similar to nP alone in maintaining HRQoL and day-to-day function relative to BL. This confirms atezo + nP had clinical benefit without compromising HRQoL, physical and role function, or worsening Tx symptoms vs P + nP in 1L mTNBC. Clinical trial information: NCT02425891.

CONTESSA: A multinational, multicenter, randomized, phase III registration study of tesetaxel plus a reduced dose of capecitabine in patients (pts) with HER2-, hormone receptor + (HR+) locally advanced or metastatic breast cancer (LA/MBC) who have previously received a taxane

TPS1107

Background: Chemotherapy treatments with robust efficacy that preserve quality of life are needed. Tesetaxel (T) is a novel, oral taxane that has potential advantages over currently available taxanes, including: oral administration with a low pill burden and Q3W dosing regimen; no observed hypersensitivity reactions; preclinical evidence of CNS penetration; and improved activity against chemotherapy-resistant tumors. Over 600 pts have been treated with T in clinical studies. T had robust monotherapy activity in a Phase 2 study in 38 pts with HER2-, HR+ MBC who received T Q3W, with a confirmed ORR per RECIST 1.1 of 45% and median PFS of 5.4 mo. The confirmed ORR in taxane-pretreated pts was 45%. Preclinical and clinical studies suggest that reducing the dose of capecitabine (C) in combination with a taxane may result in reduced toxicity without reduction in efficacy. Preclinical data also suggest that T may penetrate the brain at clinically relevant concentrations. CONTESSA investigates T plus a reduced dose of C as an all-oral regimen in HER2-, HR+ LA/MBC, with revised eligibility criteria to allow inclusion of pts with CNS metastases. Methods: CONTESSA is a 600-pt, multinational, multicenter, randomized (1:1), Phase 3 registration study comparing T (27 mg/m2 on Day 1 of a 21-day cycle) plus a reduced dose of C (1,650 mg/m2/day on Days 1-14 of a 21-day cycle) to the approved dose of C alone (2,500 mg/m2/day on Days 1-14 of a 21-day cycle) in pts with HER2-, HR+ LA/MBC previously treated with a taxane in the (neo)adjuvant setting. The protocol was newly amended to allow pts with known CNS metastases. The primary endpoint is PFS assessed by an Independent Radiologic Review Committee (IRC). CONTESSA is 90% powered to detect a 42% improvement in PFS (HR = 0.71). Secondary endpoints are OS, ORR, and disease control rate. Enrollment began in Dec 2017. Following review in Jan 2019, the Independent Data Monitoring Committee recommended that the Study continue as planned. Clinical trial information: NCT03326674.

ATTAIN: Phase III study of etirinotecan pegol versus treatment of physician's choice in patients with metastatic breast cancer and brain metastases

The increasing incidence of breast cancer brain metastases is a major clinical problem with its associated poor prognosis and limited treatment options. The long-acting topoisomerase-1 inhibitor, etirinotecan pegol, was designed to preferentially accumulate in tumor tissue including brain metastases, providing sustained cytotoxic SN38 levels. Motivated by improved survival findings from subgroup analyses from the Phase III BEACON trial, this ongoing randomized, Phase III trial compares etirinotecan pegol to drugs commonly used for advanced breast cancer in patients with stable, treated breast cancer brain metastases who have been previously treated with an anthracycline, taxane and capecitabine. The primary end point is overall survival. Secondary end points include objective response rate, progression-free survival and time to CNS disease progression or recurrence in patients with/without CNS lesions present at study entry. Trial registration number: NCT02915744.

A large collection of integrated genomically characterized patient-derived xenografts highlighting the heterogeneity of triple-negative breast cancer

Triple-negative breast cancer (TNBC) represents 10% of all breast cancers and is a very heterogeneous disease. Globally, women with TNBC have a poor prognosis, and the development of effective targeted therapies remains a real challenge. Patient-derived xenografts (PDX) are clinically relevant models that have emerged as important tools for the analysis of drug activity and predictive biomarker discovery. The purpose of this work was to analyze the molecular heterogeneity of a large panel of TNBC PDX (n = 61) in order to test targeted therapies and identify biomarkers of response. At the gene expression level, TNBC PDX represent all of the various TNBC subtypes identified by the Lehmann classification except for immunomodulatory subtype, which is underrepresented in PDX. NGS and copy number data showed a similar diversity of significantly mutated gene and somatic copy number alteration in PDX and the Cancer Genome Atlas TNBC patients. The genes most commonly altered were TP53 and oncogenes and tumor suppressors of the PI3K/AKT/mTOR and MAPK pathways. PDX showed similar morphology and immunohistochemistry markers to those of the original tumors. Efficacy experiments with PI3K and MAPK inhibitor monotherapy or combination therapy showed an antitumor activity in PDX carrying genomic mutations of PIK3CA and NRAS genes. TNBC PDX reproduce the molecular heterogeneity of TNBC patients. This large collection of PDX is a clinically relevant platform for drug testing, biomarker discovery and translational research.

Abstract GS3-07: Clinical utility of circulating tumor cell count as a tool to chose between first line hormone therapy and chemotherapy for ER+ HER2- metastatic breast cancer: Results of the phase III STIC CTC trial

Background: In ER+ HER2- metastatic breast cancer (MBC) patients, the clinical choice between 1st line hormone therapy (HT, the recommended option) or chemotherapy (CT) is based on the absence of “visceral crisis” or adverse prognostic factors, with no proven/objective criteria. In that context, STIC CTC (NCT01710605) was set up as a strategy trial to test whether circulating tumor cells (CTC) count could help customize the choice between 1st line HT or CT.

Methods: For this multicenter phase 3 non-inferiority trial, the main inclusion criteria were: ER+ HER2- MBC with no prior therapy, PS≤2, no contra-indication to HT or CT and informed consent. The a priori treatment choice (HT or CT) and CTC count (CellSearch®) were obtained in all patients prior to randomization. Patients were randomized 1:1 between clinically-driven choice (CTC count not disclosed, HT or CT administered as decided a priori), or a CTC-driven choice (HT if &lt;5 CTC/7.5ml, CT if ≥5 CTC/7.5ml). The primary objective was treatment efficacy (PFS hazard ratio), non-inferiority being established if the upper bound of the PFS HR 2-sided 90%CI is ≤1.25; secondary objectives included subgroup analyses (CTC status, patient characteristics) and OS.

Results: 761 MBC patients were randomized between 02/2012 and 08/2016. Baseline characteristics: 7.8% of patients had a PS=2, 24.1% had a de novo metastatic disease; 63.3% received prior adjuvant HT and 49.9% prior adjuvant CT; 31.3% had ≥3 metastatic sites. A priori treatments (HT or CT) and CTC count (&lt; or ≥5 CTC/7.5ml) were well balanced between the two arms. After randomization, in the clinically-driven arm, N=267 (72.4%) patients received HT and N=102 (27.6%) CT (as decided a priori). In the CTC-driven arm: (1) the a priori choice of HT was confirmed by a low CTC count in N=181 (67.5%) of patients, while N=87 (32.5%) were switched to CT due to a high CTC count; (2) the a priori choice of CT was confirmed by high CTC count in only N=48 (48%) patients, while N=52 (52%) were switched to HT. The primary endpoint was met, PFS being not inferior in the CTC-driven arm (HR=0.98, 90%CI=[0.84–1.13]). Analyses focusing on discordant subgroups showed that for patients with a priori choice of HT but with high CTC count (leading to a switch to CT in the CTC-arm), PFS was significantly longer in the CTC-driven arm than in the standard arm (HR=0.67, 95%CI=[0.49–0.92]; p=0.01), with a non-significant trend toward longer OS (HR=0.68, 95%CI=[0.44–1.07]; p=0.09). Inversely, for patients with a priori choice of CT but with low CTC count (i.e. de-escalation to HT in the CTC arm), PFS was not statistically different between the two arms.

Conclusion: This trial demonstrates the clinical utility of CTC count as an objective decision tool when considering 1st line therapy in ER+ HER2- MBC. In most patients, CTC count did confirm the a priori clinical choice; however, trial results show that in discrepant cases, CTC count may be trusted for either escalating (i.e. considering CT in patients if high CTC count) or de-escalating (i.e. considering HT in patients if low CTC count) 1st line therapy.

Funding: French National Cancer Institute; Menarini Silicon Biosystems.

Citation Format: Bidard F-C, Jacot W, Dureau S, Brain E, Bachelot T, Bourgeois H, Goncalves A, Ladoire S, Naman H, Dalenc F, Gligorov J, Espie M, Levy C, Ferrero J-M, Loirat D, Cottu P, Dieras V, Simondi C, Berger F, Alix-Panabieres C, Pierga J-Y. Clinical utility of circulating tumor cell count as a tool to chose between first line hormone therapy and chemotherapy for ER+ HER2- metastatic breast cancer: Results of the phase III STIC CTC trial [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 GS3-07.

Abstract PD1-11: nextMONARCH 1: Phase 2 study of abemaciclib plus tamoxifen or abemaciclib alone in HR+, HER2- advanced breast cancer

Background

Abemaciclib is a selective CDK4 & 6 inhibitor approved on a continuous dosing schedule for HR+, HER2- advanced breast cancer (ABC) as monotherapy (MONARCH 1) and in combination with endocrine therapy (ET). A previous Phase 1b (NCT01394016) cohort of HR+ ABC patients (pts) demonstrated efficacy of abemaciclib monotherapy (150mg and 200mg Q12H starting dose); given the small sample size and nonrandomized design the impact of the starting dose was unclear. nextMONARCH 1 (NCT02747004) evaluated abemaciclib in 2 monotherapy arms, in a randomized setting. Abemaciclib has been associated with dose-dependent early onset diarrhea that is well managed with antidiarrheal therapy. nextMONARCH 1 also explored the 200mg Q12H abemaciclib dose in combination with prophylactic loperamide to reduce incidence/severity of diarrhea and dose adjustments. A third arm evaluated abemaciclib + tamoxifen as a strategy to overcome endocrine resistance.

Methods

nextMONARCH 1 is a multicenter, randomized, open-label, Phase 2 study of abemaciclib or abemaciclib + tamoxifen in women with HR+, HER2- ABC who have progressed on or after prior ET and previously received chemotherapy. Pts were stratified by presence of liver metastases and prior use of tamoxifen in the advanced setting. Randomization was 1:1:1 to abemaciclib 150mg Q12H + daily tamoxifen 20mg (Arm A) or abemaciclib 150mg Q12H (Arm B); or abemaciclib 200mg Q12H + prophylactic loperamide (Arm C). Key eligibilities were ≥2 chemotherapy regimens (1-2 administered in metastatic setting), measurable disease and no prior treatment with CDK4 & 6 inhibitors. Primary objective was progression free survival (PFS). Key secondary objectives included objective response rate (ORR), dclinical benefit rate (CBR), and safety. PFS analysis tested superiority of Arm A to C at ∼110 events across the 2 arms assuming a hazard ratio (HR) of 0.667 to achieve ∼80% power. Arm B would be considered non-inferior to Arm C if the observed PFS HR is &lt;1.2.

Results

234 pts were randomized to Arms A (n=78), B (n=79) and C (n=77). 166 PFS events have been observed (A: 57; B: 54; C: 55). Median PFS was 9.1 months in Arm A, 6.5 in Arm B and 7.4 in Arm C (A vs C: HR=.815, 95% CI, .556-1.193, p=.293; B vs C: HR=1.045, 95% CI, .711-1.535 p=.811). Investigator-assessed ORR was 34.6%, 24.1% and 32.5% (confirmed ORR: 25.6%, 19.0%, 28.6%) and CBR was 61.5%, 49.4% and 51.9% in Arms A, B and C, respectively. Prophylactic loperamide reduced the incidence and severity of diarrhea (C: 62.3%, Gr 3: 7.8%) compared to MONARCH 1 (90.2%, Gr 3: 19.7%, Dickler et al. 2017) resulting in similar rates of diarrhea with 150mg abemaciclib without prophylaxis (A: 53.8%, Gr 3: 1.3%; B: 67.1%, Gr 3: 3.8%). The adverse event profile across arms was generally consistent with other breast studies of abemaciclib.

Conclusions

nextMONARCH 1 confirmed single-agent activity of abemaciclib in heavily pretreated pts with HR+, HER2- ABC. Efficacy of abemaciclib monotherapy at 150mg was similar to 200mg. Combining tamoxifen with abemaciclib did not demonstrate a statistically significant improvement in PFS compared to abemaciclib monotherapy. Addition of prophylactic loperamide to abemaciclib 200mg resulted in diarrhea similar to 150mg without prophylaxis.

Citation Format: Hamilton E, Cortes J, Dieras V, Ozyilkan O, Chen S-C, Petrakova K, Manikhas A, Jerusalem G, Hegg R, Lu Y, Bear MM, Johnston EL, Martin M. nextMONARCH 1: Phase 2 study of abemaciclib plus tamoxifen or abemaciclib alone in HR+, HER2- advanced breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD1-11.

Abstract P6-18-19: Real-world survival of heavily pretreated patients with refractory HR+, HER2- metastatic breast cancer receiving single-agent chemotherapy - A comparison with MONARCH 1

Background

In MONARCH 1 (NCT02102490), abemaciclib demonstrated promising single-agent activity and tolerability in a population of heavily pretreated women with refractory HR+, HER2- metastatic breast cancer (MBC).1 Confirmed objective response rate (ORR) was 19.7% (95% CI: 13.3, 27.5) and at 18 months minimum follow-up median overall survival (OS) was 22.3 months. Due to the single-arm trial design of MONARCH 1, there is a need to view these results in clinical context relative to available treatment options. This study compared the OS results of abemaciclib in MONARCH 1 vs that in a real-world single-agent chemotherapy cohort with similar patient and disease characteristics.

Methods

MONARCH 1 study design and key eligibility criteria were previously described.1 The real-world cohort was based on Flatiron Health electronic health records-derived, nationally representative (USA-based) database comprising patient-level structured and unstructured data, curated via technology-enabled abstraction, for patients with MBC between January 1, 2011 through February 28, 2018. A real-world single-agent chemotherapy cohort was created based on the key eligibility criteria of MONARCH 1 and included patients diagnosed with HR+, HER2- MBC who received single-agent chemotherapy (eribulin, capecitabine, gemcitabine, or vinorelbine) following 1-2 prior chemotherapy regimens in the metastatic setting, had an ECOG PS of 0-1, and no prior CDK4 & 6 therapy. The index date was the start of the eligible single-agent chemotherapy, and patients were followed from the index date until date of death, loss to follow-up, or end of the database, whichever occurred earlier. OS results were adjusted using 2 methods (Mahalanobis distance matching and entropy balancing with bootstrapping) to account for baseline demographic and clinical differences between the real-world and trial cohorts.

Results

A real-world cohort (n=281) with eligibility criteria similar to the MONARCH 1 population (n=132) was identified. A subsequent matching based on Mahalanobis distance was performed to match MONARCH 1 population (n=108) with the real-world cohort (n=108). The matched cohorts demonstrated similar patient and disease characteristics. Median OS was 22.3 months in the abemaciclib arm vs 13.6 months in the matched cohort with an estimated hazard ratio (HR) of 0.54 (95% CI: 0.37, 0.77). Results of a sensitivity analysis performed using entropy balancing were consistent with an adjusted median OS of 12.7 months in the real-world cohort (n=281)with HR of 0.57 (95% CI from bootstrapping: 0.44, 0.78).

Conclusion

Methodological advances to adjust for potential biases, and improvements in data quality, have evolved enabling the ability to leverage a real-world cohort as an external comparator arm. This study demonstrates the ability to create a real-world chemotherapy cohort suitable to serve as a comparator for MONARCH 1. These exploratory results suggest a survival advantage and adequately place the clinical benefit of abemaciclib monotherapy in clinical context.

References

Dickler et al, CCR 2017

Citation Format: Rugo H, Dieras V, Cortes J, Patt D, Wildiers H, O'Shaughnessy J, Zamora E, Yardley DY, Carter GC, Sheffield KM, Li L, Andre VA, Derbyshire RE, Li XI, Frenzel M, Huang Y-J, Dickler MN, Tolaney SM. Real-world survival of heavily pretreated patients with refractory HR+, HER2- metastatic breast cancer receiving single-agent chemotherapy - A comparison with MONARCH 1 [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-18-19.

Phase I study of onapristone, a type I antiprogestin, in female patients with previously treated recurrent or metastatic progesterone receptor-expressing cancers

INTRODUCTION

Onapristone is a type I progesterone receptor (PR) antagonist, which prevents PR- mediated DNA transcription. Onapristone is active in multiple preclinical models and two prior studies demonstrated promising activity in patients with breast cancer. We conducted a study of extended release (ER) Onapristone to determine a recommended dose and explore the role of transcriptionally-activated PR (APR), detected as an aggregated subnuclear distribution pattern, as a predictive biomarker.

METHODS

An open-label, multicenter, randomized, parallel-group, phase 1 study (target n = 60; NCT02052128) included female patients ≥18 years with PRpos tumors. APR analysis was performed on archival tumor tissue. Patients were randomized to five cohorts of extended release (ER) onapristone tablets 10, 20, 30, 40 or 50 mg BID, or immediate release 100 mg QD until progressive disease or intolerability. Primary endpoint was to identify the recommended phase 2 dose. Secondary endpoints included safety, clinical benefit and pharmacokinetics.

RESULTS

The phase 1 dose escalation component of the study is complete (n = 52). Tumor diagnosis included: endometrial carcinoma 12; breast cancer 20; ovarian cancer 13; other 7. Median age was 64 (36-84). No dose limiting toxicity was observed with reported liver function test elevation related only to liver metastases. The RP2D was 50 mg ER BID. Median therapy duration was 8 weeks (range 2-44), and 9 patients had clinical benefit ≥24 weeks, including 2 patients with APRpos endometrial carcinoma.

CONCLUSION

Clinical benefit with excellent tolerance was seen in heavily pretreated patients with endometrial, ovarian and breast cancer. The data support the development of Onapristone in endometrial endometrioid cancer. Onapristone should also be evaluated in ovarian and breast cancers along with APR immunohistochemistry validation.

Phase Ib study evaluating safety and clinical activity of the anti-HER3 antibody lumretuzumab combined with the anti-HER2 antibody pertuzumab and paclitaxel in HER3-positive, HER2-low metastatic breast cancer

Purpose To investigate the safety and clinical activity of comprehensive human epidermal growth factor receptor (HER) family receptor inhibition using lumretuzumab (anti-HER3) and pertuzumab (anti-HER2) in combination with paclitaxel in patients with metastatic breast cancer (MBC). Methods This phase Ib study enrolled 35 MBC patients (first line or higher) with HER3-positive and HER2-low (immunohistochemistry 1+ to 2+ and in-situ hybridization negative) tumors. Patients received lumretuzumab (1000 mg in Cohort 1; 500 mg in Cohorts 2 and 3) plus pertuzumab (840 mg loading dose [LD] followed by 420 mg in Cohorts 1 and 2; 420 mg without LD in Cohort 3) every 3 weeks, plus paclitaxel (80 mg/m2 weekly in all cohorts). Patients in Cohort 3 received prophylactic loperamide treatment. Results Diarrhea grade 3 was a dose-limiting toxicity of Cohort 1 defining the maximum tolerated dose of lumretuzumab when given in combination with pertuzumab and paclitaxel at 500 mg every three weeks. Grade 3 diarrhea decreased from 50% (Cohort 2) to 30.8% (Cohort 3) with prophylactic loperamide administration and omission of the pertuzumab LD, nonetheless, all patients still experienced diarrhea. In first-line MBC patients, the objective response rate in Cohorts 2 and 3 was 55% and 38.5%, respectively. No relationship between HER2 and HER3 expression or somatic mutations and clinical response was observed. Conclusions Combination treatment with lumretuzumab, pertuzumab and paclitaxel was associated with a high incidence of diarrhea. Despite the efforts to alter dosing, the therapeutic window remained too narrow to warrant further clinical development.

TRIAL REGISTRATION

on ClinicalTrials.gov with the identifier NCT01918254 first registered on 3rd July 2013.

Abstract OT3-05-06: EarLEE-2: A phase 3 study of ribociclib + endocrine therapy (ET) for adjuvant treatment of patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–), intermediate-risk, early breast cancer (EBC)

Background: Adjuvant ET with or without chemotherapy reduces the risk for recurrence of HR+, HER2– EBC. However, recurrence is still common, especially in patients with adverse clinical and pathologic features. In the phase 3 MONALEESA-2 trial, the cyclin-dependent kinase 4/6 inhibitor ribociclib (LEE011), in combination with letrozole, prolonged progression-free survival versus letrozole plus placebo in postmenopausal women with HR+, HER2– advanced breast cancer and no prior therapy for advanced disease (HR = 0.56, 95% CI, 0.43-0.72; P = 3.29×10−6; Hortobagyi et al. N Engl J Med. 2016). EarLEE-2 is investigating the efficacy and safety of ribociclib with ET versus placebo with ET as adjuvant treatment in patients with intermediate-risk EBC.

Trial design: In this double-blind, placebo-controlled, phase 3 adjuvant trial, ˜4,000 women and men with fully resected, intermediate-risk, HR+, HER2– EBC (defined as AJCC 8th ed. Prognostic Stage Group II) are being randomized 1:1 to oral ribociclib (600 mg/day, 3 weeks on/1 week off for ˜24 months) plus ET or to placebo plus ET. Adjuvant ET may include tamoxifen, letrozole, anastrozole, or exemestane for ≥ 60 months with ovarian suppression for premenopausal women at the discretion of the investigator. Adjuvant ET in men will be tamoxifen only. Neoadjuvant therapy is not permitted. Randomization is stratified by menopausal status (men and premenopausal women vs postmenopausal women), prior adjuvant chemotherapy (yes vs no), Prognostic Stage Group (IIA vs IIB), and geographic region (North America/Europe/Australia vs rest of the world). Eligible patients must have tumor tissue from the surgical specimen, adequate bone marrow and organ functions, normal serum electrolytes, QTc interval &lt; 450 msec, and completed and recovered from acute toxicities of adjuvant radiotherapy and/or chemotherapy. The primary endpoint is invasive disease-free survival (per STEEP system; Hudis et al. J Clin Oncol. 2007). Secondary endpoints include recurrence-free survival, distant disease-free survival, overall survival, quality of life, and safety. Global recruitment to EarLEE-2 is ongoing. NCT03081234

Citation Format: O'Shaughnessy J, Alba E, Bardia A, Dent S, Dieras V, Hortobagyi G, Im S-A, Montemurro F, Untch M, Yardley DA, Chakravartty A, Germa C, Miller M, Slamon D. EarLEE-2: A phase 3 study of ribociclib + endocrine therapy (ET) for adjuvant treatment of patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–), intermediate-risk, early breast cancer (EBC) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT3-05-06.

Abstract P5-19-01: Impact of palbociclib plus letrozole on patient-reported general health status compared with letrozole alone in ER+/HER2- advanced/metastatic breast cancer

BACKGROUND: Palbociclib plus letrozole significantly improved progression-free survival (PFS) compared with letrozole plus placebo in treatment-naive postmenopausal patients with estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC) in the phase 3 PALOMA-2 trial. Here, we compare patient-reported general health status with extended (max 53 cycles) follow-up (data cut off May31st, 2017) (Pfizer: NCT01740427).

METHODS: PALOMA-2 randomized patients 2:1 to palbociclib + letrozole (n=444) or placebo + letrozole (n=222). Patient-reported outcomes were assessed at baseline, day 1 of cycles 1, 2, and 3, and day 1 of every other cycle from cycle 5 until the end of treatment using the EuroQol 5-Dimension Questionnaire (EQ-5D). The EQ-5D is a standardized measure of health status that consists of a descriptive system comprising the following 5 dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression rated at 3 levels (no, some, or extreme problems) and a single index score for health status (ranges generally from 0 [dead] to 1 [full health]) calculated using a standard algorithm. In addition, a visual analog scale (VAS) measured self-rated health status from 0 (worst imaginable) to 100 (best imaginable). Repeated measures mixed-effects analyses were performed to compare overall index and VAS scores between treatments, controlling for baseline.

RESULTS: Completion rates at baseline were &gt;95% in each group. The mean (SD) scores at baseline were comparable between palbociclib plus letrozole and letrozole alone for the VAS (71.3 [21.2] vs 72.3 [19.8]) and the EQ-5D index scores (0.70 [0.25]) vs (0.73 [0.21]). Median follow up was 38 months for palbociclib plus letrozole and 37 months for letrozole only. No statistically significant difference in overall change from baseline in general health status was observed between the treatment arms. The proportion of patients reporting the presence of a problem at baseline was similar for palbociclib plus letrozole and letrozole, respectively: mobility (39% vs 39%), self-care (12% vs 12%), usual activities (44% vs 39%), pain (69% vs 65%), and anxiety/depression (54% vs 54%). No statistically significant difference in overall mean EQ-5D index scores (0.73 vs. 0.71) was observed between the treatment arms.

CONCLUSION: Addition of palbociclib to letrozole maintained general health status and EQ-5D index scores in ER+ HER2- advanced/metastatic breast cancer with no statistically significant differences observed compared to letrozole alone.

Citation Format: Harbeck N, Dieras V, Finn R, Gelmon KA, Walshe JM, Shparyk Y, Mori A, Lui DR, Bhattacharyya H, Iyer S, Johnston S, Rugo HS. Impact of palbociclib plus letrozole on patient-reported general health status compared with letrozole alone in ER+/HER2- advanced/metastatic 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 P5-19-01.

Abstract P5-20-03: Impact of prior adjuvant trastuzumab (aT) on clinical characteristics, patterns of recurrence and outcome in 2863 patients with Her2 positive (HER2+) metastatic breast cancer (MBC)- Results from the French ESME UNICANCER program

Background: The management of HER2+ BC has changed dramatically with the introduction and widespread use of HER2-targeted therapies, especially in the adjuvant setting. However, there is relatively limited real-world information on the impact of adjuvant Trastuzumab (aT) on patterns of recurrence and outcome of HER2+ MBC.

Methods: In 2014, the 18 French Cancer Centers launched the Epidemiological Strategy and Medical Economics (ESME) program to provide real-world data on MBC patients (pts). All pts who started a 1st-line treatment for MBC between 01-Jan-2008 and 31-Dec-2014 were included. We examined clinical characteristics and outcomes (overall survival [OS] and time to next treatment [TNT]) in patients with HER2+ MBC pretreated with trastuzumab in the adjuvant setting (aT) compared with trastuzumab-naïve patients (nT) and patients with de novo HER2+ MBC (dn). Multivariate analyses adjusted for baseline demographic, prognostic factors and year of diagnosis (prior or after 2005, when aT was approved and widely administered in France for early HER2+ breast cancer).

Results: Among the 15170 pts of the ESME database, 2863 (19%) were HER2+: 1093 pts (38%) had de novo and 1765 pts (62%) recurrent MBC; 63% were Hormone Receptor (HR) +; 54%, 25% and 21% had respectively 1, 2, or &gt; 2 metastatic sites (68% visceral and 12% brain). Median time to 1st metastasis was 43.4 months (m) (95% CI: 24.6-84.4): 54 m in HR+ and 30 m in HR-. Among pts with recurrent MBC, 55% (995) had received aT. As 1st-line therapy for MBC, 90 % of pts received HER2-targeted agents (73% T-based). With a median follow-up of 46 m, median OS is 45 m (95% CI: 42.5-48). OS is significantly higher in de novo compared to recurrent MBC: 54 m (95% CI: 50.2-60.4) vs. 38.4 m (95% CI: 36.7-41.9), (p &lt; 0.0001). Among pts with recurrent cancers, median OS is inferior in pts who had received aT, as compared to those who had not: 33.4 m (95% CI: 29.6-36.7) vs. 49.5 m (95% CI: 44.3-56.8), (p &lt; 0.0001). Statistically significant differences persist after adjustment for age at MBC, disease-free interval, metastatic sites and RH status in the multivariate model (HR=1.45, 95% CI: 1.26-1.67) but not after adjustment for year of diagnosis (prior or after 2005) (HR=0.90, 95% CI: 0.70-1.15).

Conclusions: These large-scale real-world data in patients with HER2+ MBC provide evidence that the survival outcome remain similar in patients with failure of adjuvant trastuzumab compared with trastuzumab-naïve patients after adjustment for year of diagnosis. De novo HER2+ MBC pts have the best outcomes. Data on clinical characteristics of metastasis and time to next treatment for the three subgroups will be presented at the meeting.

Citation Format: Saghatchian M, Carton M, Piot I, Pérol D, Pistilli B, Brain E, Ghouadni A, Ricci F, Vanlemmens L, Loeb A, Levy C, Goncalves A, Dalenc F, Lefeuvre-Plesse C, Campone M, Jaffre A, Gourgou S, Cailliot C, Robain M, Dieras V. Impact of prior adjuvant trastuzumab (aT) on clinical characteristics, patterns of recurrence and outcome in 2863 patients with Her2 positive (HER2+) metastatic breast cancer (MBC)- Results from the French ESME UNICANCER 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 P5-20-03.

Abstract P1-17-03: Abemaciclib for the treatment of brain metastases secondary to hormone receptor positive breast cancer

Background: Although a lower percentage of patients with hormone receptor-positive (HR+) metastatic breast cancer (MBC) develop brain metastases when compared with triple negative and HER2+ MBC patients, there are no regulatory approved systemic agents for the treatment of HR+ breast cancer brain metasteses, and this remains an unmet medical need. Standard local treatment options include surgery, stereotactic radiosurgery (SRS), and/or whole brain radiation therapy (WBRT). Abemaciclib, an oral selective CDK4 and 6 inhibitor administered on a continuous dosing schedule, has demonstrated clinical activity and an acceptable safety profile in heavily pre-treated HR+ MBC patients. Preclinically, abemaciclib crosses the blood-brain barrier, which is further supported clinically by detectable levels of abemaciclib similar to plasma levels in resected brain metastases in a subset of patients with HR+, HER2- MBC as previously reported for the current study. Together these data provide further rationale for evaluating abemaciclib in patients with brain metastases.

Methods: Study I3Y-MC-JPBO (NCT02308020) is an open-label, Phase 2, Simon 2-Stage trial evaluating the safety and efficacy of abemaciclib up to 200 mg BID in 4 cohorts of patients with brain metastases secondary to HR+ MBC, NSCLC, or melanoma. With regard to HR+ MBC, one cohort included HR+, HER2- patients, another one included HR+/HER2+ patients. All HR+ MBC patients enrolled to 1 of these 2 cohorts were required to have at least 1 measurable brain lesion. The primary objective was objective intracranial response rate as defined by Response Assessment in Neuro-Oncology brain metastases response criteria. Stage 1 was to enroll 23 evaluable patients per study part; if ≥2 respond to abemaciclib, 33 additional evaluable patients were to be enrolled to Stage 2. Secondary CNS objectives include best overall response, duration of response, and clinical benefit rate.

Results: For Stage 1 efficacy, in patients with HR+, HER2+ MBC futility was met. However, for HR+, HER2- patients, 2 confirmed, durable partial responses were observed and enrollment to Stage 2 is ongoing.

Conclusions: Previously, this study provided evidence that abemaciclib penetrates brain metastases in patients with HR+, HER2- MBC. The current results provide sufficient evidence of anti-tumor activity on brain metastases in patients with HR+, HER2- MBC to merit further exploration, but not for patients with HR+, HER2+ disease. Safety and tolerability results are similar to those previously reported for abemaciclib, with the majority of adverse events being gastrointestinal.

Citation Format: Bachelot T, Kabos P, Yardley D, Dieras V, Costigan T, Klise S, Awada A. Abemaciclib for the treatment of brain metastases secondary to hormone receptor positive breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-17-03.

Abstract P5-21-03: Palbociclib (PAL) + letrozole (LET) as first-line therapy in estrogen receptor–positive (ER+)/human epidermal growth factor receptor 2–negative (HER2−) advanced breast cancer (ABC): Efficacy and safety updates with longer follow-up across patient subgroups

BACKGROUND: Endocrine therapy (ET) has been the primary first-line (1L) therapy for ER+ ABC. In the PALOMA-2 study (NCT01740427), PAL (P)+LET (L) significantly prolonged progression-free survival (PFS; HR=0.58, P&lt;.001) after a median 23 mo follow-up (FU) (Finn et al. NEJM 2016). Here we report more mature PFS overall and in subgroups, with (w/) longer FU. The study is ongoing for overall survival FU.

METHODS: Postmenopausal pts w/ ER+/HER2- ABC and no prior systemic therapy in the ABC setting were randomized 2:1 to P (125 mg/d) + L (2.5 mg QD) or placebo (PBO) + L. Key endpoints: investigator-assessed PFS and safety. Median PFS (mPFS) was estimated (intent-to-treat population).

RESULTS: 666 pts (444, P+L; 222, PBO+L) were enrolled. Arms were well balanced: visceral (48%)/nonvisceral (52%) disease and prior ET (56%)/no prior ET (44%). After a median FU of 38 mo w/ P+L and 37 mo w/ PBO+L, mPFS was 27.6 and 14.5 mo, respectively, in the overall population (HR=0.56, P&lt;.0001; Table).

TABLE. mPFS overall and by relevant subgroupsP+LPBO+LP+L vs PBO+LmPFS, mo (95% CI)mPFS, mo (95% CI)HR (95% CI)P* Overall27.6 (22.4–30.3)14.5 (12.3–17.1)0.56 (0.46–0.69)&lt;.0001 Measurable disease23.7 (19.3–27.6)14.5 (12.3–18.5)0.63 (0.50–0.79)&lt;.0001 Nonmeasurable disease36.2 (27.6?NE)16.5 (8.3–19.6)0.39 (0.25–0.60)&lt;.0001 Visceral19.3 (16.4–24.2)12.3 (8.4–16.4)0.62 (0.47–0.81)&lt;.0005 Nonvisceral35.9 (27.7–NE)17.0 (13.8–24.8)0.50 (0.37–0.67)&lt;.0001 Bone only†36.2 (27.6–NE)11.2 (8.2–22.0)0.41 (0.26–0.63)&lt;.0001 Not bone only24.2 (19.4–27.7)14.5 (12.9–18.5)0.62 (0.50–0.78)&lt;.0001 De novo metastatic27.9 (22.1–33.4)22.0 (13.9–27.4)0.61 (0.44–0.85)&lt;.005 Prior ET24.2 (18.8–27.6)11.2 (8.4–14.5)0.54 (0.42–0.71)&lt;.0001 No prior ET30.3 (24.5–35.7)21.9 (15.9–27.4)0.59 (0.43–0.80)&lt;.0005 Nonvisceral36.2 (27.9–NE)27.6 (19.1–35.6)0.59 (0.38–0.92)&lt;.01 Visceral23.7 (16.8–30.3)13.9 (10.2–22.2)0.55 (0.36–0.85)&lt;.005 Disease sites130.4 (24.8–NE)16.5 (11.0–22.1)0.52 (0.36–0.75)&lt;.0005228.1 (19.4–NE)16.3 (11.0–27.4)0.57 (0.37–0.89)&lt;.01323.7 (19.2–27.6)13.8 (8.8–17.0)0.61 (0.46–0.82)&lt;.0005NE=not estimable. *Not adjusted for multiple analyses; 1-sided P values. †Per tumor site.

All subgroups benefited from addition of P to L. Notably, pts w/ low disease burden (bone only, nonvisceral disease, few disease sites) derived significant PFS benefit, including those w/ both nonvisceral disease and no prior ET (mPFS, 36.2 vs 27.6 mo; HR=0.59, P&lt;.01). Importantly, median time from randomization to start of 2nd subsequent systemic anticancer therapy was 39 vs 29 mo for P+L vs PBO+L (HR=0.72, P&lt;.005). There were no new safety signals w/ longer FU.

CONCLUSIONS: This is the longest FU of a phase 3 study of a cyclin-dependent kinase 4/6 inhibitor for ABC. P+L continues to consistently improve PFS vs PBO+L across all subgroups while toxicity remains manageable; notably P+L delays time to starting 2nd subsequent anticancer therapies by 10 mo. Pts w/ low disease burden or sensitivity to ET alone had PFS &gt;3 y (significant vs PBO+L), demonstrating the clinical benefit of P+ET. These data confirm P+L should be a 1L therapy option for pts w/ HR+/HER2- ABC.

Funding: Pfizer

Citation Format: Rugo HS, Finn RS, Dieras V, Ettl J, Lipatov O, Joy A, Harbeck N, Castrellon A, Lu DR, Mori A, Gauthier ER, Huang C, Gelmon KA, Slamon DJ. Palbociclib (PAL) + letrozole (LET) as first-line therapy in estrogen receptor–positive (ER+)/human epidermal growth factor receptor 2–negative (HER2−) advanced breast cancer (ABC): Efficacy and safety updates with longer follow-up across patient subgroups [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 P5-21-03.

Palbociclib (PAL) + letrozole (L) as first-line (1L) therapy (tx) in estrogen receptor-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2−) advanced breast cancer (ABC): Efficacy and safety across patient (pt) subgroups

1039

Background: Hormone tx (HT) is the primary 1L tx for ER+ ABC. In the PALOMA-2 study (NCT01740427), PAL+L as 1L ABC tx prolonged progression-free survival (PFS; hazard ratio [HR] 0.58; P<.001) (Finn et al, NEJM. 2016). Methods: Postmenopausal pts with ER+/HER2– ABC and no prior systemic treatment in the advanced setting were randomized 2:1 to PAL (125 mg/d oral [3 wk on, 1 wk off]) + L (2.5 mg QD) or placebo (P) + L. Key endpoints were investigator-assessed PFS and safety. Results: 666pts (444, PAL+L; 222, P+L) were enrolled. Pts were similarly distributed between arms for visceral (48%) and nonvisceral (52%) disease and prior HT (56%) and no prior HT (44%); more pts had disease-free interval (DFI) >12 mo (40%) than ≤12 mo (22%). Median PFS (mPFS) was improved in all subgroups by adding PAL to L (Table). Adverse events were consistent across subgroups, as described for the full study population. Conclusions: PAL+L improved mPFS vs P+L with manageable toxicity across all subgroups including those with visceral disease. PAL+L provides a 1L option that should be considered for all pts with ER+/HER2- ABC. Sponsor: Pfizer Clinical trial information: NCT01740427. [Table: see text]

Evolution of overall survival according to year of diagnosis (2008-2014) and subtypes, among 16703 metastatic breast cancer (MBC) patients included in the real-life "ESME" cohort

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Background: Real-life data may help checking that public investments match closely medical needs. During the last decade, several drugs have been released on the market for MBC on the basis of a potential impact on overall survival (OS). Based on the large real-life ESME cohort, we aimed to describe the time evolution of MBC OS according to main phenotypes. Methods: ESME is a unique MBC national cohort including all consecutive patients (pts) who initiated treatment for MBC between 1/01/08 and 31/12/14 in the 18 French comprehensive cancer centres. ESME collects retrospective data using clinical trial-like methodology including quality assessments. Database lock was 8/12/2016. Primary objective was the impact of year of MBC diagnosis on OS. Multivariate Cox regressions were used with adjustment for main prognostic covariates. Results: 15170 out of 16703 pts in ESME had full IHC data allowing their classification as HR+HER2- (N=9922), HER2+ (N=2863), or HR-HER2- (N=2321) cases. Median FU and OS for the whole cohort are 4.05 yrs [95 CI: 3.98-4.12], and 3.1 yrs [95 CI: 3.03-3.18] respectively. In the adjusted multivariate analysis, year of MBC diagnosis, age at MBC, subtype (using HER2+ as reference), disease-free interval (DFI), visceral involvement, and number (nbr) of metastatic sites are significant OS predictors (table) although with low effect for the first item. Age at MBC, DFI, visceral involvement, and nbr of metastatic sites remained significant prognostic variables in subtypes. Year of diagnosis was no longer significant in HR+HER2- nor HR-HER2- cases (HR=0.997, p=0.71 and HR=0.997, p=0.84), while it was highly significant in HER2+ cases (HR=0.91, p<0.0001). Conclusions: Although OS of MBC has slightly improved over the past decade, this remains mostly confined to HER2+ cases, highlighting the need for new strategies for the luminal and triple negative populations. [Table: see text]

ATTAIN: Phase 3 study of etirinotecan pegol (EP) vs treatment of physician's choice (TPC) in patients (pts) with metastatic breast cancer (MBC) who have stable brain metastases (BM) previously treated with an anthracycline, a taxane, and capecitabine (ATC)

TPS1120

Background: EP is a next generation topoisomerase I inhibitor-polymer conjugate that provides continuous exposure to SN-38, the active metabolite. A BM mouse model showed high penetration and retention of SN-38 in CNS lesions, resulting in decreased size of CNS lesions and improved survival (OS) at concentrations achieved at the recommended dose in pts (Adkins BMC Cancer 2015). A Phase 3 trial (BEACON) of EP vs TPC in 852 pts with advanced BC did not meet its primary endpoint of OS (HR 0.087; p = 0.08); a subset of 67 pts with stable BM showed improved OS (HR 0.51 [95% CI 0.30-0.86]; p < 0.01) (Perez Lancet Oncol 2015). The current Phase 3 trial (ATTAIN) was designed for this subpopulation of pts having high unmet medical need. Methods: Pts with MBC with locally treated stable BM will be randomized 1:1 to EP vs TPC in an open-label, randomized Phase 3 study. Eligibility includes ECOG PS 0 or 1; adequate organ function who received prior ATC (in neo/adjuvant or locally advanced/MBC setting); pts must have had ≥1 prior cytotoxic regimen for MBC (triple negative BC); ≥2 prior cytotoxic regimens and either 1 prior hormone therapy (HR+ BC) or 1 prior HER2 targeted therapy (HER2+ BC). Pts must have undergone definitive local therapy of BM (whole brain radiation [RT]; stereotactic RT or surgical resection as single-agent or combination); signs/symptoms of BM must be stable with steroids unchanged or decreasing for ≥7 days prior to randomization. Primary endpoint is OS. Key secondary endpoints: ORR and PFS by RECIST v1.1 and RANO-BM, clinical benefit rate (ORR+SD ≥ 6 months) and QoL. Pts randomized to TPC will receive 1 of 7 IV cytotoxic agents. Pts are stratified by region, PS and receptor status. 350 pts will be randomized to obtain number of events required at 90% power to detect a statistically significant improvement in OS (hypothesizing HR = 0.67); 1 interim analysis at 50% of deaths (130 events) will be performed. PK sampling and UGT1A1 testing will be performed in the EP arm; plasma ctDNA will be assessed for potential predictive markers of efficacy. Enrollment will begin early 2017. Clinical trial information: NCT02915744.

First-line Bevacizumab and Paclitaxel for HER2-negative Metastatic Breast Cancer: A French Retrospective Observational Study

AIM

To assess outcomes in patients treated with first-line bevacizumab-containing therapy for human epidermal growth factor receptor (HER)2-negative metastatic breast cancer (mBC) at a single centre with a homogenous standard-of-care.

PATIENTS AND METHODS

Information on patient and disease characteristics, efficacy, and safety was extracted from computer-based records of all patients receiving first-line bevacizumab-paclitaxel at the Curie Institute, Paris, France, between 2008 and 2011.

RESULTS

Median progression-free survival in the 116 treated patients was 13.2 months; median overall survival was 38.4 months. Corresponding values were 9.0 and 18.8 months, respectively, in patients with triple-negative mBC, and 19.4 and 58.8 months, respectively, in patients receiving maintenance endocrine therapy. No new safety signals were seen.

CONCLUSION

Outcomes in patients treated with bevacizumab-paclitaxel at our center were consistent with efficacy in prospective clinical trials, with notable activity in poor-prognosis disease. Maintenance endocrine or oral therapy with bevacizumab after paclitaxel discontinuation was associated with long-term disease control.