Fulvestrant ('Faslodex')--a new treatment option for patients progressing on prior endocrine therapy

Since its introduction more than 30 years ago, tamoxifen has been the most widely used endocrine therapy for the treatment of women with advanced breast cancer. More recently, a number of alternative endocrine treatments have been developed, including several selective estrogen receptor modulators (SERMs), aromatase inhibitors (AIs) and, most recently, fulvestrant ('Faslodex'). Fulvestrant is an estrogen receptor (ER) antagonist, which, unlike the SERMs, has no known agonist (estrogenic) effect and downregulates the ER protein. Tamoxifen is effective and well tolerated, although the non-steroidal AIs, anastrozole and letrozole, are more effective treatments for advanced disease than tamoxifen. Fulvestrant has recently gained US Food and Drug Administration approval for the treatment of hormone receptor-positive metastatic breast cancer in postmenopausal women with disease progression following antiestrogen therapy. In two global phase III clinical trials fulvestrant was at least as effective and as equally well tolerated as anastrozole for the treatment of postmenopausal women with advanced and metastatic breast cancer. In a retrospective analysis of the combined data from these trials, mean duration of response was significantly greater for fulvestrant compared with anastrozole. These new hormonal treatments expand the choice of endocrine therapy for women with advanced breast cancer and offer new options for sequencing and combining treatments.