Fulvestrant: A Review in Advanced Breast Cancer Not Previously Treated with Endocrine Therapy

Fulvestrant (Faslodex^®), a selective estrogen receptor (ER) degrader, is now indicated for the treatment of ER+ or hormone-receptor positive (HR+)/HER2- advanced breast cancer in postmenopausal women previously untreated with endocrine therapy. In the phase 3 FALCON trial conducted in this setting, intramuscular fulvestrant 500 mg/month (plus an additional dose at 2 weeks) was significantly more effective in prolonging progression-free survival (PFS) than oral anastrozole 1 mg/day (particularly in patients with non-visceral disease), with this benefit seemingly driven by fulvestrant recipients responding significantly longer to treatment. Other efficacy measures, including objective response rate, did not significantly or markedly differ between the two regimens and median overall survival was not yet calculable. Fulvestrant was generally well tolerated in this trial, displaying an overall tolerability profile consistent with its known tolerability in other breast cancer settings. Thus, monotherapy with intramuscular fulvestrant is a generally well tolerated and more effective treatment option than standard-of-care anastrozole for ER+ or HR+/HER2- advanced breast cancer in postmenopausal women not previously treated with endocrine therapy.