Real-world effectiveness of fulvestrant monotherapy as first hormonal therapy in metastatic breast cancer patients.

Abstract

e12537 Background: Fulvestrant is a selective estrogen receptor degrader approved as monotherapy for postmenopausal women with estrogen-receptor-positive metastatic breast cancer (MBC) who progress following anti-estrogen therapy. The recent Phase 3 FALCON study for hormone therapy (HT) naïve women showed increased median progression-free survival (PFS) (16.6 months) in fulvestrant treated patients (pts) compared with anastrozole (13.8 months), but real-world data are lacking. This study examined the real-world effectiveness of fulvestrant monotherapy as first (L1) or second line (L2) treatment after MBC diagnosis. Methods: This was a retrospective medical record review from 10 US community oncology practices. Female pts initiated fulvestrant monotherapy as the first HT after MBC diagnosis, administered as L1 or as L2 treatment following L1 chemotherapy. Fulvestrant was initiated between 1/1/2011 and 12/31/2015. Pts were classified as HT naïve; and HT relapse status: early relapse (≤12 months of adjuvant HT completion), late relapse (>12 months). Time to first chemotherapy (TTC), PFS, and overall survival (OS) were evaluated using Kaplan-Meier analyses. Results: The study included 121 pts: mean (SD) age 65.7 (11.4) years, 81.8% Caucasian, 94.2% postmenopausal/undocumented, and 92.0% HER2-/undocumented. Overall, 15.7% were de novo metastatic and 86.0% initiated fulvestrant in L1. At the start of fulvestrant, 40.5% had visceral metastasis. The study results (Table 1) suggest better outcomes (TTC, PFS, OS) in HT naïve and late relapse pts, than early relapse pts. Conclusions: First line fulvestrant in the real-world setting demonstrates comparable PFS benefit to clinical trial results and appeared successful in delaying chemotherapy initiation in HT naïve and late relapse pts. This finding supports the use of fulvestrant monotherapy as the first hormonal therapy in a metastatic setting. [Table: see text]