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Using Tamoxifen for Breast Cancer Treatment and Prevention

Tamoxifen is a drug that has been used since the late 1990s to treat and prevent breast cancer in women and men. It’s one of the oldest and most prescribed medications for treating a specific type of cancer called hormone-receptor-positive breast cancer. If you have this type of breast cancer and are taking Tamoxifen, you can take comfort in the fact that its benefits and risks have been very well studied and documented.

“Tamoxifen acts like a soccer goalie. It’s a chemical compound that interferes with estrogen receptors on tissue cells, preventing estrogen from interacting with receptor,” said Anthony Scarpaci, MD, a medical oncologist specializing in breast cancer management at Jefferson Health. “In this way, it can block the growth of breast cancer tissue by interfering with the effects of estrogen in the breast tissue.”

When Is Tamoxifen Used?

For men and women with hormone-receptor-positive breast cancer, Tamoxifen is typically used to:

  • Reduce the risk for recurrence of early stage breast cancer after surgery, radiation and chemotherapy.
  • Shrink large breast cancer tumors before they are treated surgically.
  • Treat advanced stage cancers, included metastatic breast cancer.
  • Prevent breast cancer in women who have not been diagnosed, but who are at a higher risk for developing it.

“The current guideline is that women can use Tamoxifen for five years as a long-term therapy,” said Dr. Scarpaci. “However, there have been recent studies that show it may continue to have benefits for as long as 10 years. It’s about balancing those benefits with the potential side effects.”

Tamoxifen and Pregnancy

Tamoxifen works by placing a patient in a premenopausal state – similar to what a woman would experience immediately before entering menopause – by blocking estrogen from working normally in the body. Since estrogen is an important component of fertility, Tamoxifen should not be taken by women who are trying to become pregnant or who want to become pregnant in the future. Pregnant women should not take Tamoxifen, since it can cause birth defects and abnormalities in the fetus. In these cases, the patient, doctors, and genetic counselor will work together to review risk factors and identify other potential treatment options that may work for them.

“Our patients are never alone when they face tough decisions like this,” said Dr. Scarpaci. “Our patient navigation program is designed to make this type of decision less overwhelming for women battling breast cancer.”

The Potential Side Effects of Tamoxifen

The most common side effects of Tamoxifen will be similar to what a woman may experience during natural menopause, including hot flashes, vaginal dryness and vaginal bleeding. If a breast cancer patient is close to entering menopause naturally, taking Tamoxifen may make it happen sooner.

Tamoxifen also increases the risk for developing blood clots in the legs and lungs, and may increase the chances for developing uterine cancer. However, a study of women taking the drug for up to five years to lower their breast cancer risk found that only one percent of those patients were later diagnosed with uterine cancer.

“Risks associated with Tamoxifen are relatively small and well understood,” said Dr. Scarpaci. “Tamoxifen is still the standard for treatment of hormone-receptor-positive breast cancer in premenopausal patients.”

Abington has breast cancer navigators who can help coordinate appointments, answer questions and offer support. For more information, call 1-800-405-HELP.

Page last reviewed: September 15, 2017
Page last updated: September 15, 2017

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