Tamoxifen
Tamoxifen is a selective estrogen receptor modulator (SERM) used in hormone receptor–positive breast cancer — a feature of about 80% of breast cancer diagnoses. The drug binds to estrogen receptors in cancer cells and blocks estrogen's growth signal, while acting estrogen-like in other tissues such as bone. It is typically taken for several years, both before and after menopause, to reduce the risk of recurrence.
How it works
Many breast cancers carry estrogen receptors on their cells; when estrogen attaches to these receptors, it stimulates the cancer cells to divide. Tamoxifen occupies the receptors so that estrogen cannot bind, and the growth signal is not passed on. According to the National Cancer Institute, hormone therapy is usually taken for five years or more; one common approach is to take tamoxifen for two to three years and then switch to an aromatase inhibitor.
Because tamoxifen blocks estrogen in breast tissue but mimics its action elsewhere in the body, it belongs to the class of selective estrogen receptor modulators. Its common side effects — hot flashes, night sweats, and reduced interest in sex — reflect this interference with estrogen signalling.
Used in
Invasive Breast Carcinoma
C50
standard adjuvant hormone therapy in hormone receptor-positive disease, mainly before menopause