First-line vs second-line fulvestrant for hormone receptor-positive advanced breast cancer: A post-hoc analysis of...

The double-blind, phase III CONFIRM study (NCT00099437) evaluated fulvestrant 500 mg vs fulvestrant 250 mg in postmenopausal women with hormone receptor-positive locally advanced/metastatic breast cancer (LA/MBC). This post-hoc analysis investigated the efficacy and safety of fulvestrant given either first-line or second-line for advanced disease.

Progression-free survival (PFS) and overall survival (OS) with fulvestrant 500 mg vs fulvestrant 250 mg was evaluated using unadjusted log-rank tests in patients treated in the first- (progression during or within 12 months after completing adjuvant endocrine therapy; n = 387) and second-line (following endocrine therapy for LA/MBC; n = 343) settings.

First-line fulvestrant 500 mg significantly prolonged PFS vs fulvestrant 250 mg (median PFS 5.6 vs 4.2 months; hazard ratio [HR] 0.80; 95% confidence interval [CI] 0.64-1.00; p = .047). Median PFS was numerically greater with second-line fulvestrant 500 mg vs fulvestrant 250 mg (7.9 vs 6.3 months; HR 0.80; 95% CI 0.64-1.02; p = .068). At data cut-off (75.5% maturity), median OS with first-line fulvestrant 500 mg was 23.2 vs 22.1 months with fulvestrant 250 mg (HR 0.87; 95% CI 0.70-1.10; p = .251), and 29.2 vs 22.8 months, respectively, in the second-line (HR 0.75; 95% CI 0.58-0.96; p = .020). The safety profile was broadly comparable between dose groups and across treatment lines, and consistent with the overall patient population.

The superiority of fulvestrant 500 mg over fulvestrant 250 mg in patients with LA/MBC in CONFIRM was consistent in both the first- and second-line settings for PFS, and numerically greater in both settings for OS.