How does tamoxifen prevent breast cancer? Does it increase a woman's risk for other cancers?

Tamoxifen (Nolvadex) is a medication in pill form that stops or slows the activity of estrogen, a female hormone that promotes the growth of breast cancer.

Tamoxifen has been used for more than 20 years to treat patients with advanced breast cancer. It also is used for women with early-stage breast cancer. Research has shown that tamoxifen can help prevent breast cancer from returning and prevent new breast cancers from developing.

In a large study funded by the National Cancer Institute, researchers looked at the effectiveness of tamoxifen in preventing breast cancer in women who have an increased risk for developing the disease. The researchers found a 49 percent reduction in breast cancer among the women who took tamoxifen.

The study also found that tamoxifen's side effects include an increased risk of two types of cancer of the uterus. These are endometrial cancer, which develops in the lining of the uterus, and uterine sarcoma, which develops in the muscular wall of the uterus.

Women who are taking tamoxifen should have regular pelvic exams and should see a doctor promptly is they have abnormal vaginal bleeding or pelvic pain. These could be symptoms of cancers of the uterus

Still, the benefits of tamoxifen as a treatment for breast cancer are firmly established and far outweigh the potential risks. For more information about tamoxifen, talk with your doctor or call the Cancer Information Service at 1-800-4-CANCER.

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