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 and may be used in combination with other treatments. Common side effects include hot flashes, joint pain, and fatigue. Regular monitoring by a healthcare provider is essential to ensure its effectiveness and manage any potential side effects.