Anastrozole versus tamoxifen as first-line therapy for advanced breast cancer in 668 postmenopausal women: Results of the tamoxifen or arimidex randomized group efficacy and tolerability study

Purpose: To compare the efficacy and tolerability of anastrozole (Arimidex: AstraZeneca, Wilmington, DE, and Macclesfield, United Kingdom) with that o f tamoxifen as first-line therapy for advanced breast cancer (ABC) in postm enopausal women. Patients and Methods: This randomized double-blind, multicenter study evalu ated the efficacy of anastrozole 1 mg once daily relative to tamoxifen 20 m g once daily in patients with tumors that were hormone receptor-positive or of unknown receptor status who were eligible for endocrine therapy. The pr imary end points were time to progression (TTP), objective response (OR), a nd tolerability. Results: A total of 668 patients (340 in the anastrosole arm and 328 in the tamoxifen arm) were randomized to treatment and followed-up for ct median of 19 months. Median TTP wets similar for both treatments (8,2 months in pa tients who received anastrozole and 8.3 months in patients who received tam oxifen), The tamoxifen:anastrosole hazards ratio was 0.99 (lower one-sided 95% confidence limit, 0,86), demonstrating that anastrozole was at least eq uivalent to tamoxifen. Anastrozole was also as effective as tamoxifen in te rms of OR (32.9% of anastrozole and 32.6% of tamoxifen patients achieved a complete response ICR] or partial response [PR]), Clinical benefit (CR + PR + stabilization of greater than or equal to 24 weeks) rates were 56.2% and 55.5% for patients receiving anastrazole and tamoxifen, respectively. Both treatments were well tolerated, However, incidences of thromboembolic even ts and vaginal bleeding were reported in fewer patients treated with anastr ozole than with tamoxifen (4.8% v 7.3% [thromboembolic events] and 1.2% v 2 .4% [vaginal bleeding], respectively), Conclusion: Anastrozole satisfied the predefined criteria for equivalence t o tamoxifen, Together with the lower observed incidence of thromboembolic e vents and vaginal bleeding, these findings indicate that anastrozole should be considered as first-line therapy for postmenopausal women with ABC, (C) 2000 by American Society of Clinical Oncology.