What Is Tamoxifen?

Tamoxifen (Nolvadex^®) is a medication used to treat patients with breast cancer or who are at high risk for breast cancer. It can also be used to treat other kinds of cancers.

Tamoxifen works by interfering with the activity of the hormone estrogen. Estrogen feeds the growth of many (but not all) breast cancers. Tamoxifen binds to the estrogen-receptor sites in breast cells and prevents estrogen from binding to them. Because tamoxifen works against the effects of estrogen in the breast, it functions as an "anti-estrogen" in breast tissue.

How Tamoxifen Is Used

For people with early stage breast cancer, tamoxifen is used as an additional treatment (adjuvant therapy). It helps prevent the original breast cancer from returning, and it helps prevent the development of new breast cancers.

For people with advanced breast cancer, tamoxifen is used to slow or stop the growth of cancer cells that are present in the body.

For women who have not had breast cancer but are at high risk, tamoxifen can be used to reduce their chance of developing the disease. This use of tamoxifen for prevention is more common for:

• Women who carry a mutation in the breast cancer genes BRCA1 or 2
• Women who have a significant family history of breast cancer
• Women who have precancerous lesions, including atypical ductal and lobular hyperplasia and lobular carcinoma in situ

For more information about tamoxifen, you can read the National Cancer Institute's Tamoxifen Fact Sheet.