In postmenopausal women with endocrine-responsive breast cancer, adjuvant treatment with letrozole, as compared with tamoxifen, results in a higher 5-year disease-free survival (DFS) rate (84% vs. 81.4%) and in a significantly reduced risk of an event ending a DFS period (hazard ratio, 0.81). Such events included a cancer that recurred locally, regionally, or at a distant site, a new invasive cancer in the contralateral breast, or any second non-breast cancer, or death from a prior cancer.  

The findings come from The Breast International Group (BIG) 1-98 study, a randomized, Phase III, double-blind trial of over 8,000 women that looked at treatment with letrozole alone, letrozole followed by tamoxifen, tamoxifen alone, and tamoxifen followed by letrozole.  

In terms of adverse events, the women in the two groups that received letrozole initially were less likely to develop thromboembolism, endometrial cancer, and vaginal bleeding, but more likely to have skeletal and cardiac complications and hypercholesterolemia.  

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In postmenopausal women with endocrine-responsive breast cancer, adjuvant treatment with letrozole, as compared with tamoxifen, results in a higher 5-year disease-free survival (DFS) rate (84% vs. 81.4%) and in a significantly reduced risk of an event ending a DFS period (hazard ratio, 0.81). Such events included a cancer that recurred locally, regionally, or at a distant site, a new invasive cancer in the contralateral breast, or any second non-breast cancer, or death from a prior cancer.