Di Leo A, et al. - In this post-hoc analysis of the double-blind, phase III CONFIRM study, the efficacy and safety of first-line vs second-line fulvestrant for hormone receptor-positive advanced breast cancer were assessed. The superiority of fulvestrant 500 mg over fulvestrant 250 mg in patients with locally advanced/metastatic breast cancer, as demonstrated in CONFIRM, was found to be consistent in both the first- and second-line settings for progression-free survival, and numerically greater in both settings for overall survival in this present study.

• Using unadjusted log-rank tests, researchers assessed progression-free survival (PFS) and overall survival (OS) with fulvestrant 500 mg vs fulvestrant 250 mg 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.

• Findings demonstrated that 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).
• With second-line fulvestrant 500 mg vs fulvestrant 250 mg, numerically greater median PFS was noted (7.9 vs 6.3 months; HR 0.80; 95% CI 0.64–1.02; p=.068).
• Researchers found that 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).
• They also noted that the safety profile was broadly comparable between dose groups and across treatment lines, and consistent with the overall patient population.