Fulvestrant (FUL) As First-Line Therapy in HR+ve, HER2-ve Advanced Breast Cancer (ABC) Patients (pts): when Clinical Practice Comes Earlier Than Clinical Trials. Results from the GIM-13 AMBRA Study

Introduction: Hormone receptor positive tumors represent the most common form of breast cancer. Endocrine therapy (ET) represents the main initial therapeutic strategy for these patients and has been associated with significant clinical benefits. One of the available therapeutic strategy is FUL; in a Phase II study, FUL demonstrated improvements in time to progression (TTP) and overall survival (OS) in comparison to anastrozole (ANA). In a recent Phase III trial, comparing FUL vs ANA as 1st-line therapy, PFS was significantly longer in the FUL group than in the ANA group (16 = 6 vs 13 = 8 months). The benefit in PFS seems to be limited to patients without visceral sites of disease. Aim of the present analysis is to describe pts’ characteristics and outcome treated with FUL in a real-life setting. Patients and methods: We used data of the HR+ve pts of the AMBRA study, a longitudinal cohort study, describing the choice of first and subsequent lines of treatment in HER2-ve MBC pts, treated with FUL in any line of therapy to describe pts’ characteristics and outcome in terms of ORR (CR+PR) and DCR (ORR+SD) and time to treatment change (TTC). Results: So far, 791/1500 pts have been registered into the AMBRA study, 673 of them (85%) with HR+ MBC: 197 (29.3%) pts received FUL in any setting and 125 (18.6%) as 1st-line therapy. Median DFI was 74 months (14-420). Main sites of metastasis were bone in 69 pts (55.2%) and viscera in 43 (34.4%). ORR was 24% in the whole population, 24.6% and 18.6% in pts with bone and visceral metastases, respectively. Median TTC was 14.63 months (range 1.17-96.70) in the whole population, 3.8 months in pts with visceral involvement and 25.7 in those with bone disease. Conclusions: Our data are very close to those obtained in the FALCON trial and strongly support the use of FUL as 1st-line therapy mainly in pts with metastatic disease limited to bone.