Outcome beyond third-line chemotherapy for metastatic triple-negative breast cancer in the French ESME program

{Purpose: Among metastatic breast cancer (MBC) patients, those with a triple-negative breast cancer phenotype (mTNBC) have the worst prognosis, but the benefit of chemotherapy beyond second line on outcome remains uncertain. The purpose of this study was to identify predictive factors of outcome after third-or fourth-line chemotherapy. Methods: The ESME-MBC database is a French prospective real-life cohort with homogeneous data collection, including patients who initiated first-line treatment for MBC (2008-2016) in 18 cancer centers. After selection of mTNBC cases, we searched for independent predictive factors (Cox proportional-hazards regression models) for overall survival (OS) on third-and fourth-line chemotherapy (OS3, OS4). We built prognostic nomograms based on the main prognostic factors identified. Results: Of the 22,266 MBC cases in the ESME cohort, 2903 were mTNBC, 1074 (37%) and 598 (20%) of which had received at least 3 or 4 lines of chemotherapy. PFS after first-and second-line chemotherapy (PFS1, PFS2) and number of metastatic sites >3 at baseline were identified by multivariate analysis as prognostic factors for both OS3 (HR = 0.76 95%CI[0.66-0.88]