['To compare the efficacy and tolerability of fulvestrant (formerly ICI 182,780) and anastrozole in postmenopausal women with advanced breast cancer progressing after prior endocrine treatment.', 'Patients (n = 451) with advanced breast cancer were randomized to receive fulvestrant 250 mg as a once-monthly (one x 5 mL) intramuscular injection or an oral dose of anastrozole 1 mg in this open, parallel-group, multicenter trial. The primary end point was time to progression (TTP). Secondary end points included objective response (OR) rates, defined as complete response (CR) or partial response (PR), duration of response (DOR), and tolerability.', 'Patients were followed for a median period of 14.4 months. In terms of TTP, fulvestrant was as effective as anastrozole (hazard ratio, 0.98; confidence interval [CI], 0.80 to 1.21; P =.84). Median TTP was 5.5 months for fulvestrant and 5.1 months for anastrozole. OR rates showed a numerical advantage for fulvestrant (20.7%) over anastrozole (15.7%) (odds ratio, 1.38; CI, 0.84 to 2.29; P =.20). Clinical benefit rates (CR + PR + stable disease > or = 24 weeks) were 44.6% for fulvestrant and 45.0% for anastrozole. Median DOR was 14.3 months for fulvestrant and 14.0 months for anastrozole. Both treatments were well tolerated, with 3.2% and 1.3% of fulvestrant- and anastrozole-treated patients, respectively, withdrawn from treatment because of an adverse event.'] Is fulvestrant , formerly ICI 182,780 , as effective as anastrozole in postmenopausal women with advanced breast cancer progressing after prior endocrine treatment?