On Oct. 29, 2004, the U.S. Food and Drug Administration (FDA) approved Letrozole for the extended adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer. The approval was based on promising disease-free survival (DFS) results from a double-blind, multicenter study. However, the follow-up was insufficient to determine long-term outcomes.

Letrozole was granted accelerated approval by the FDA for the adjuvant treatment on December 28, 2005. Accelerated approval was based on promising disease-free survival (DFS) results, but follow-up was insufficient to determine long-term outcomes for both safety and efficacy. The treatment duration was 24 months for both studies and patients were followed for a median of 26 months and 28 months in the adjuvant and extended adjuvant trials, respectively.