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A comparison of letrozole and tamoxifen in postmenopausal women with early breast cancer
Journal Paper/Review - Dec 29, 2005
Breast International Group (BIG) 1-98 Collaborative Group, Price Karen N, Wardly Andrew, Wardley Andrew, Smith Ian, Rabaglio Manuela, Gelber Richard D, Castiglione-Gertsch Monica, Paridaens Robert, Forbes John F, Mauriac Louis, Mouridsen Henning, Coates Alan S, Keshaviah Aparna, Thürlimann Beat, Goldhirsch Aron
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BACKGROUND: The aromatase inhibitor letrozole is a more effective treatment for metastatic breast cancer and more effective in the neoadjuvant setting than tamoxifen. We compared letrozole with tamoxifen as adjuvant treatment for steroid-hormone-receptor-positive breast cancer in postmenopausal women. METHODS: The Breast International Group (BIG) 1-98 study is a randomized, phase 3, double-blind trial that compared five years of treatment with various adjuvant endocrine therapy regimens in postmenopausal women with hormone-receptor-positive breast cancer: letrozole, letrozole followed by tamoxifen, tamoxifen, and tamoxifen followed by letrozole. This analysis compares the two groups assigned to receive letrozole initially with the two groups assigned to receive tamoxifen initially; events and follow-up in the sequential-treatment groups were included up to the time that treatments were switched. RESULTS: A total of 8010 women with data that could be assessed were enrolled, 4003 in the letrozole group and 4007 in the tamoxifen group. After a median follow-up of 25.8 months, 351 events had occurred in the letrozole group and 428 events in the tamoxifen group, with five-year disease-free survival estimates of 84.0 percent and 81.4 percent, respectively. As compared with tamoxifen, letrozole significantly reduced the risk of an event ending a period of disease-free survival (hazard ratio, 0.81; 95 percent confidence interval, 0.70 to 0.93; P=0.003), especially the risk of distant recurrence (hazard ratio, 0.73; 95 percent confidence interval, 0.60 to 0.88; P=0.001). Thromboembolism, endometrial cancer, and vaginal bleeding were more common in the tamoxifen group. Women given letrozole had a higher incidence of skeletal and cardiac events and of hypercholesterolemia. CONCLUSIONS: In postmenopausal women with endocrine-responsive breast cancer, adjuvant treatment with letrozole, as compared with tamoxifen, reduced the risk of recurrent disease, especially at distant sites. (ClinicalTrials.gov number, NCT00004205.)