Assessment of multiple endocrine therapies for metastatic breast cancer in a multicenter national observational study

1052 Background: For HR+/HER2– metastatic breast cancer (mBC), International guidelines recommend multiple lines of endocrine therapy (ET) before starting chemotherapy. Few studies have assessed the efficacy of such strategy on large populations. Our objective was to evaluate multiple ET activity according to clinical and biological characteristics and type of ET. Methods: All patients (pts) who initiated treatment for a newly diagnosed mBC between January 2008 and December 2014 in all 18 French Comprehensive Cancer Centers were included in the real life ESME database. ESME collects retrospective data using a clinical trial-like methodology. Database lock was 8 Dec 2016. Primary endpoint of the current study was progression free survival (PFS) on successive ET lines. Only pts with ET alone were assessed (pts receiving ET after chemotherapy as maintenance therapy, or combined with targeted treatment were excluded). Results: 9921 pts out of 16703 in ESME, had HR+/HER2- mBC (median age 62.0 years[range 23-96]). 53.9% of pts had visceral and 80.1% non visceral disease at diagnosis. Median OS of HR+/HER2- pts was 42.15 months (95% CI, 40.93-43.27). As first-line therapy, 4123 pts (41.6%) received ET alone, while 2038 received chemotherapy alone (20.5%) and 3667 received both (37%). Median PFS for first-line ET (N=4123) was 11.3 months (95% CI, 10.6-11.9). Only 668 pts (16%) received subsequent lines of ET alone. Types of ET used are described in the table below. Successive PFS will be reported at the meeting. Conclusions: Those data show that ET is prescribed to less than 50% of patients with HR+/HER2- mBC in first line and only to a small minority in subsequent lines. This is not in line with existing guidelines (NCCN, ABC3). Real-life median PFS for first-line ET is consistent with median PFS reported in clinical trials (Nabholtz, 2000). [Table: see text]