Efficacy of fulvestrant in the treatment of postmenopausal women with endocrine-resistant advanced breast cancer in routine clinical practice.

Abstract

This study aimed to describe the efficacy of fulvestrant 500mg in postmenopausal women with estrogen receptor (ER)-positive advanced/metastatic breast cancer who had disease progression after receiving anti-estrogen therapy in clinical practice, getting real-world data. Multicenter, retrospective, observational study conducted in Spain. Postmenopausal women with locally advanced/metastatic ER-positive breast cancer who received treatment with fulvestrant 500mg after progression with a previous anti-estrogen therapy were eligible. The primary endpoint was progression-free survival (PFS); secondary endpoints were overall survival (OS), clinical benefit rate (CBR), duration of clinical benefit (DoCB), and safety profile. A total of 263 women were evaluated (median age, 65.8years). At a median follow-up of 21.5months, median PFS and OS were 10.6 and 43.2months, respectively. PFS according to 1st, 2nd, 3rd, and≥4th lines were 11.5, 10.6, 9.9, and 8.5months, respectively (p=0.0245). PFS in patients with visceral involvement was 10months vs 10.6months in patients without visceral involvement (p=0.6604), 9.6months in patients with high Ki67 vs 10months in patients with low Ki67 (p=0.7224), and 10.2months in HER2+patients vs 10.3months in HER2- patients (p=0.6809). The CBR was 56.5% and the DoCB was 18.4months. The most frequently adverse events were injection site pain (10.3%) and musculoskeletal disorders (7.6%). Fulvestrant 500mg administered in clinical practice was shown to be effective (PFS, 10.6months; CBR, 56.5%) and well tolerated, in accordance with previous trials.