Efficacy of Fulvestrant in Heavily Pretreated Postmenopausal Women with Advanced Breast Cancer: A Preliminary Report

Purpose: Fulvestrant, a potent estrogen receptor (ER) antagonist with a novel mechanism of action, has shown efficacy in pre-treated patients with advanced breast cancer. We assessed the efficacy and tolerability of fulvestrant in Korean postmenopausal women. Methods: Of the 25 candidates identified at Asan Medical Center, Seoul, Korea, six were deemed ineligible due to inadequate baseline and follow-up imaging. The 19 patients included in this retrospective analysis received the approved dose of fulvestrent (250 mg intramuscular injection, once per month) as second- (n=8), third- (n=7), or fourth-line (n=4) endocrine therapy. Results: At a median follow-up of 7.4 months (range, 1.2-34.8 months), the 19 patients received a median of four cycles (range, 1-34 cycles) of fulvestrant. Median time to progression was 5.5 months (95% confidence interval [CI], 0.4-10.7 months), and median overall survival was 17.9 months (95% CI, 2.7-33.1 months). Among 17 evaluable patients, one (5.3%) achieved a partial response, 10 (52.6%) showed stable disease, and six (31.6%) showed progressive disease. The clinical benefit rate was 26.3%. Four patients (21.1%) reported adverse events, but all were grade 1 or 2. Conclusion: Fulvestrant was effective and well tolerated in patients with advanced breast cancer who had been previously treated with several lines of endocrine and chemotherapeutic agents.