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; AstraZenec a, Wilmington, DE, and Macclesfield, United Kingdom) and tamoxifen were com pared as first-line therapy for advanced breast cancer in 353 postmenopausa l women. Patients and Methods: The randomized, double-blind, multicenter study was d esigned 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 en d 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 + stabilizatio n greater than or equal to 24 weeks) observed in 59% of patients on anastro zole and 46% on tamoxifen (two-sided P =,0098, retrospective analysis). Ana strozole had a significant advantage over tamoxifen in terms of TTP (median TTP of 11.1 and 5.6 months for anastrozole and tamoxifen, respectively; tw o-sided P =.005), The tamoxifen:anastrozole hazards ratio was 1.44 (lower o ne-sided 95% confidence limit, 1,16), Both treatments were well tolerated, However, thromboembolic events and vaginal bleeding were reported in fewer patients who received anastrozole compared with those who received tamoxife n (4.1% v 8.2% [thromboembolic events] and 1.2% v 3.8% [vaginal bleeding], respectively). Conclusion: Anastrozole satisfied the predefined criteria far equivalence t o tamoxifen, Furthermore, we observed both a significant increase in TTP an d a lower incidence of thromboembolic events and vaginal bleeding with anas trozole. These findings indicate that anastrozole should be considered as f irst-line therapy for postmenopausal women with advanced breast cancer. (C) 2000 by American Society of Clinical Oncology.