Progression-free survival results in postmenopausal Asian women: subgroup analysis from a phase III randomized trial of fulvestrant 500 mg vs anastrozole 1 mg for hormone receptor-positive advanced breast cancer (FALCON)

Abstract

Background: The international, phase III FALCON study (NCT01602380) in postmenopausal patients with hormone receptor-positive, locally advanced/metastatic breast cancer (LA/MBC) who had not received prior endocrine therapy, demonstrated statistically significant improvement in progression-free survival (PFS) for patients who received fulvestrant 500 mg vs anastrozole 1 mg. This subgroup analysis evaluated PFS in Asian (randomized in China, Japan, or Taiwan) and non-Asian patients from the FALCON study.

Methods: Eligible patients (estrogen receptor- and/or progesterone receptor-positive LA/MBC; World Health Organization performance status 0-2; ≥ 1 measurable/non-measurable lesion[s]) were randomized. PFS was assessed via Response Evaluation Criteria in Solid Tumours version 1.1, surgery/radiotherapy for disease worsening, or death (any cause). Secondary endpoints included: objective response rate, clinical benefit rate, duration of response, and duration of clinical benefit. Consistency of effect across subgroups was assessed via hazard ratios and 95% confidence intervals (CIs) using a log-rank test. Adverse events (AEs) were evaluated.

Results: Of the 462 randomized patients, the Asian and non-Asian subgroups comprised 67 and 395 patients, respectively. In the Asian subgroup, median PFS was 16.6 and 15.9 months with fulvestrant and anastrozole, respectively (hazard ratio 0.81; 95% CI 0.44-1.50). In the non-Asian subgroup, median PFS was 16.5 and 13.8 months, respectively (hazard ratio 0.79; 95% CI 0.62-1.01). Secondary outcomes were numerically improved with fulvestrant vs anastrozole in both subgroups. AE profiles were generally consistent between Asian and non-Asian subgroups.

Conclusions: Results of this subgroup analysis suggest that treatment effects in the Asian patient subgroup are broadly consistent with the non-Asian population.

Keywords: Anastrozole; Asian; Fulvestrant; Progression-free survival; Safety.