Letrozole: a well-tolerated and effective treatment for breast cancer

Letrozole, an aromatase inhibitor, demonstrates consistent superiority over tamoxifen in various treatment settings, has the only significant survival advantage according to results from a Phase III randomized trial, and is the only aromatase inhibitor approved as an extended adjuvant therapy in the treatment of breast cancer. Initial adjuvant letrozole significantly prolongs disease-free survival, especially reducing the risk of distant metastasis, and offers a significant disease-free survival benefit to patients at an increased risk of relapse (node-positive and chemotherapy-treated patients) when compared with tamoxifen. These findings led to its recommendation as an initial adjuvant therapy in the latest St Gallen guidelines. Similar findings were reported when letrozole was administered after completion of 5 years of adjuvant tamoxifen. The benefit of letrozole also increases with the duration of treatment. Overcoming the development of resistance to endocrine therapy is under investigation. As a potent aromatase inhibitor, letrozole is the ideal drug for tailored combination treatment regimens of the future.