Letrozole is a medication primarily used to treat certain types of breast cancer in postmenopausal women. It works by lowering estrogen levels in the body, which can help slow or stop the growth of hormone-sensitive tumors. This drug is often prescribed after surgery or radiation therapy to reduce the risk of cancer returning. Letrozole is taken orally, usually once a day, and may have side effects such as hot flashes, joint pain, and fatigue. Regular monitoring by a healthcare provider is essential during treatment.