Fulvestrant is a drug treatment of hormone receptor-positive metastatic breast cancer in postmenopausal women with disease progression following anti-estrogen therapy. It is an estrogen receptor antagonist with no agonist effects, which works by down-regulating the estrogen receptor. It is administered as a once-monthly injection. Fulvestrant is a selective estrogen receptor down-regulator (SERD). Fulvestrant is indicated for the treatment of hormone receptor positive metastatic breast cancer in postmenopausal women with disease progression following anti-estrogen therapy. The dosing schedule for fulvestrant remains under investigation in an attempt to optimize its effectiveness. Fulvestrant provided effective second-line therapy in this setting for postmenopausal women who had relapsed or progressed after previous endocrine therapy.