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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 diseas, especially at distant sites.
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 hormonerecept-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 be selected were enrolled, 4003 in the letrozole group and 4007 in the tamoxifen group. After a median follow-up of 25.8 months, 351 events occurred in the letrozole group and 428 events in the tamoxifen group, with five-year disease-free survival estimates of 84.0 percent compared with 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) Of the patients with leukemia who had a higher incidence of skeletal and cardiac disease (hazard ratio, 0.73; 95 percent confidence interval, 0.60 to 0.88; P = 0.001) 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 dise as, especially at distantsites.