Letrozole belogns to a group of medicines called aromatase inhibitors. It is a hormonal (or "endocrine") breast cancer treatment. Growth of breast cancer is frequently stimulated by oestrogens, which are female sex hormones. Letrozole reduces the amount of oestrogen by blocking an enzyme (aromatase) involved in the production of oestrogens. As a consequence tumour cells slow or stop the growing and/or spreading to other parts of the body.
Letrozole is also used to prevent breast tumour spreading to other parts of the body in patients with advanced disease. Letrozole should only be used for:
- oestrogen receptor-positive breast cancer and,
- only in women after menopause i.e. cessation of periods.