Anastrozole, a potent and selective aromatase inhibitor, versus megestrol acetate in postmenopausal women with advanced breast cancer: results of overview analysis of two phase III trials. Arimidex Study Group.

PURPOSETo compare the efficacy and tolerability of anastrozole (1 and 10 mg once daily), a selective, oral, nonsteroidal aromatase inhibitor, and megestrol acetate (40 mg four times daily), in postmenopausal women who progressed following tamoxifen treatment.PATIENTS AND METHODSTwo randomized, double-blind for anastrozole, open-label for megestrol acetate, parallel-group, multicenter trials were conducted in 764 patients. Because both trials were identical in design, an analysis of the combined results was performed to strengthen interpretation of results from each trial.RESULTSThe median follow-up duration was approximately 6 months. The estimated progression hazards ratios were 0.97 (97.5% confidence interval [CI], 0.75 to 1.24) for anastrozole 1 mg versus megestrol acetate and 0.92 (97.5% CI, 0.71 to 1.19) for anastrozole 10 mg versus megestrol acetate. The overall median time to progression was approximately 21 weeks. Approximately one third of patients in each group benefited from treatment. Twenty-s...