Tamoxifen is used to treat breast cancer that has spread to other parts of the body. This is called metastatic breast cancer. Tamoxifen is also used after surgery to reduce the risk of the cancer coming back in other parts of the body. When used this way, it is called adjuvant therapy. Tamoxifen's effectiveness depends on many different factors.
Age is one of the most important.
In post-menopausal women, tamoxifen has been an effective treatment at many different stages of breast cancer. When taken after surgery, it decreases the chance of the cancer coming back in these women. It also improves overall survival. Tamoxifen can also be an effective treatment for pre-menopausal women in specific situations, such as metastatic breast cancer. Regardless of age, tamoxifen works best in women who's cancer cells need estrogen to grow.