Anastrozole Is Superior to Tamoxifen as First-Line Therapy for Advanced Breast Cancer in Postmenopausal Women: Results of a North American Multicenter Randomized Trial

PURPOSE: The efficacy and tolerability of anastrozole (Arimidex; AstraZeneca, Wilmington, DE, and Macclesfield, United Kingdom) and tamoxifen were compared as first-line therapy for advanced breast cancer in 353 postmenopausal women. PATIENTS AND METHODS: The randomized, double-blind, multicenter study was designed to evaluate anastrozole 1 mg once daily relative to tamoxifen 20 mg once daily in patients with hormone receptor–positive tumors or tumors of unknown receptor status who were eligible for endocrine therapy. Primary end points were objective response (OR), defined as complete (CR) or partial (PR) response, time to progression (TTP), and tolerability. RESULTS: Anastrozole was as effective as tamoxifen in terms of OR (21% v 17% of patients, respectively), with clinical benefit (CR + PR + stabilization ≥ 24 weeks) observed in 59% of patients on anastrozole and 46% on tamoxifen (two-sided P = .0098, retrospective analysis). Anastrozole had a significant advantage over tamoxifen in terms of TTP (medi...