About Tamoxifen 1. Tamoxifen has been used for more than 20 years to treat patients with advanced breast cancer. It has also been used as adjuvant, or additional, therapy following surgery or radiation therapy for early stage breast cancer. Tamoxifen has recently been found to reduce the incidence of breast cancer in women at high risk of developing this 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. 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 already present in the body. As adjuvant therapy, tamoxifen has been shown to help prevent the original breast cancer from returning and also prevent the development of new cancers in the opposite breast.