Tamoxifen has been used for more than 20 years to treat patients with advanced breast cancer. It is used as adjuvant, or additional, therapy following primary treatment for early stage breast cancer. In women at high risk of developing breast cancer, tamoxifen reduces the chance of developing the disease.
Tamoxifen continues to be studied for the prevention of breast cancer.
It is also being studied in the treatment of several other types of cancer. It is important to note that tamoxifen is also used to treat men with breast cancer. Estrogen promotes the growth of breast cancer cells. Tamoxifen works against the effects of estrogen on these cells. As a treatment for breast cancer, the drug slows or stops the growth of cancer cells that are present in the body.