Abstract PD10-11: Efficacy of Platinum-based first-line chemotherapy among metastatic breast cancer (MBC) patients according to the germline BRCA1/2 mutational status: An analysis of the French ESME MBC database
Authors: Jacot William , Lusque Amélie , Mailliez Audrey , De la Motte Rouge Thibault , Cabel Luc , Levy Christelle , Patsouris Anne , Desmoulins Isabelle , Uwer Lionel , Leheurteur Marianne , Robain Mathieu , Caron Olivier , Bachelot Thomas , Filleron Thomas , Frenel Jean-Sébastien , Delaloge Suzette 
Published: February 2021

Abstract
Background: Platinum-based chemotherapy regimens (PtCT) have been shown to increase treatment efficacy when combined to neoadjuvant standard of care treatment of triple negative breast cancers (TNBC). In the metastatic breast cancer (MBC) setting, preclinical and clinical data suggest that PtCT could be more efficient than non-platinum based ones (non-PtCT) among patients (pts) with germline BRCA1/2 mutations (gBRCAm). However, published data remain controversial on this topic, particularly for MBC. We evaluated the progression-free (PFS) and overall survival (OS) under first-line PtCT and non-PtCT among gBRCAm carriers in ESME, a nationwide real-life MBC database. Methods: ESME MBC database (NCT03275311), is a unique national cohort of all consecutive pts who initiated a first-line treatment for MBC between 2008 and 2016 in one of the 18 French Comprehensive Cancer Centers. Women with HER2- MBC and known hormone receptors (HR) and gBRCA1/2 (before or in the 6 first months of metastatic disease, gBRCAm / wild type / not tested) status, who received a first-line MBC CT were selected. Patients with other germinal mutations were considered as wild type. Primary objectives were OS and PFS under first-line CT (PtCT vs. non-PtCT) in the TNBC gBRCA1/2m population.Secondary objectives were OS and PFS during first-line CT (PtCT vs. non-PtCT) in the TNBC wild-type and “not tested” population, as well as among the HR+/HER2- pts.To avoid guarantee time bias related to oncogenetic testing, analyses were performed at baseline (CT initiation) and different landmark time points (3-month or 6-month after CT initiation). Thus, BRCA status was defined according to oncogenetic testings performed before the landmark time, and patients who progressed or censored before the landmark time were excluded. Results: 10,164 pts (2,794 TNBC; 7,370 HR+/HER2-) were included in this analysis. Pts who received PtCT were significantly younger, affected by a gBRCA1/2m, had a high histological grade and/or TNBC tumor, with more frequent visceral and central nervous system spreading than non PtCT ones. Median follow-up was 51.1 months [95%CI 49.6; 52.6]. All reported results were based on the gBRCA status defined at CT initiation and on multivariable analysis adjusted on age at MBC diagnosis, de novo MBC status, type and number of metastases. In the gBRCA1/2m TNBC population (N=132), PtCT was independently associated with a better PFS compared to non-PtCT (HR=0.56, 95%CI 0.38-0.84, p=0.005), without significant difference in OS (HR=0.79, 95%CI 0.51-1.23, p=0.29).No difference was seen in wild-type BRCA1/2 TNBC pts (N=269) according to the CT regimen, while, in the larger population of untested TNBC (N=2,393), PtCT was associated with worse OS (HR=1.18, 95%CI 1.03-1.34, p=0.016) compared to non-PtCT regimens, without significant difference in PFS (HR=1.07, 95%CI 0.95-1.22, p=0.26). No significant difference was seen regarding PFS nor OS in gBRCA1/2m HR+/HER2- pts (N=124) and in the wild-type BRCA1/2 HR+/HER2- population.However, in the larger population of untested HR+/HER2- pts (N=6,836), PtCT was independently associated with worse OS (HR=2.15, 95%CI 1.79-2.59, p&lt;0.001) and PFS (HR=1.57, 95%CI 1.33-1.86, p&lt;0.001) compared to non-PtCT regimens. Results were similar in landmark analyses at 3-month or 6-month after CT initiation. Conclusions: This large-scale real-life analysis suggests higher efficacy of PtCT in term of PFS in gBRCA1/2m TNBC pts. The small sample size and post-1st line treatments may preclude observing a significant OS difference. PtCT appeared however associated with worse outcomes in untested TNBC and HR+/HER2- pts. These results emphasize the need for BRCA1/2 characterization before considering these regimens in the MBC setting.
Citation Format: William Jacot, Amélie Lusque, Audrey Mailliez, Thibault De la Motte Rouge, Luc Cabel, Christelle Levy, Anne Patsouris, Isabelle Desmoulins, Lionel Uwer, Marianne Leheurteur, Mathieu Robain, Olivier Caron, Thomas Bachelot, Thomas Filleron, Jean-Sébastien Frenel, Suzette Delaloge. Efficacy of Platinum-based first-line chemotherapy among metastatic breast cancer (MBC) patients according to the germline BRCA1/2 mutational status: An analysis of the French ESME MBC database [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 PD10-11.