Letrozole: advancing hormone therapy in breast cancer.

Letrozole is a type 2 aromatase inhibitor, which reduces availability of estrogen in postmenopausal women, thereby decreasing its ability to stimulate breast cancer cells. Phase III trials in both the advanced and early breast cancer setting have shown an improvement in disease-free survival compared with other compounds, including tamoxifen. Letrozole is well-tolerated, with the main adverse effects reported as hot flushes, arthritis, arthralgia and myalgia, and a trend towards increased risk of fracture.