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Medicines may help prevent breast cancer

There is no sure way to prevent breast cancer. But there are medicines you can take that may reduce your risk for the disease.

Known as chemoprevention, the use of drugs to reduce the risk of cancer in healthy women is an ongoing area of cancer research. Studies have shown that drugs such as tamoxifen and raloxifene may reduce the risk of breast cancer in women known to be at an increased risk for the disease, according to the American Cancer Society (ACS). Learn more about the risk factors for breast cancer here.

To help you better understand how chemoprevention may work, the ACS and the National Cancer Institute offer these answers to the following basic questions.

Q: What is tamoxifen?

A: Tamoxifen is part of a class of drugs called selective estrogen receptor modulators (SERMs). Tamoxifen works against breast cancer by interfering with the effects of estrogen—a female hormone that can promote the growth of cancer cells in the breast tissue.

Tamoxifen was originally approved as a treatment for breast cancer in the 1970s. It was approved as a prevention drug in 1998.

Q: Are there other benefits of taking tamoxifen?

A: Yes. While tamoxifen acts against the effects of estrogen in breast tissue, it acts like estrogen in other tissue. It can help prevent osteoporosis and control blood cholesterol levels.

Q: Are there risks in taking tamoxifen?

A: Yes. Women who take tamoxifen may have an increased risk of endometrial cancer, which develops in the lining of the uterus. The drug may also increase the risk of developing blood clots in the lungs or major veins.

Other side effects may include hot flashes, vaginal discharge, vaginal dryness and night sweats. Some research indicates that tamoxifen may increase the risks of cataracts.

Q: What is raloxifene?

A: Raloxifene is also a SERM and, like tamoxifen, it works by halting the effects of estrogen on breast cells. The U.S. Food and Drug Administration approved raloxifene to help prevent breast cancer in women past menopause who have osteoporosis or are at high risk for breast cancer.

Q: Are there other benefits of taking raloxifene?

A: Yes. Compared to tamoxifen, raloxifene has a much lower risk of causing cancer of the uterus and problems with serious blood clots. Raloxifene, like tamoxifen, has also been found to help prevent osteoporosis.

Q: Are there risks in taking raloxifene?

A: Yes. Women taking raloxifene may be at an increased risk of developing blood clots in the lungs or legs. Other side effects may include hot flashes, night sweats and vaginal dryness.

However, unlike tamoxifen, raloxifene doesn't appear to increase the risk of endometrial cancer.

Q: Are there other drugs that may be used to prevent breast cancer?

A: Aromatase inhibitors are newer drugs that are used to treat advanced breast cancer and to help prevent breast cancer from returning after surgery. Aromatase inhibitors work in a slightly different way than tamoxifen and raloxifene. Instead of blocking estrogen receptors, they stop a key enzyme, known as aromatase, from converting other hormones into estrogen. This lowers estrogen levels and helps keep breast cancer cells from growing. Aromatase inhibitors have not yet been approved to reduce the risk of breast cancer.

Q: How do I know whether a chemoprevention drug is right for me?

A: Research continues into the use of drugs to prevent breast cancer. If you have questions about your risk for breast cancer or the possible use of drugs to prevent the disease, talk to your doctor.

Along with chemoprevention, the ACS says you can also reduce your risk for breast cancer through lifestyle changes such as exercising regularly, maintaining a healthy weight and not drinking alcohol.

reviewed 2/18/2019

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