Anti-Estrogen Drugs to Treat Breast Cancer

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Tamoxifen is the most commonly prescribed anti-estrogen drug. Drugs such as tamoxifen are used to reduce breast cancer risk in women at increased risk of getting cancer. It is also used as adjuvant (additional) therapy to treat ductal carcinoma and for metastatic disease (that has spread). Taking tamoxifen as adjuvant therapy after initial treatment with surgery, usually for 5 years, reduces the chances of hormone receptor-positive breast cancers coming back.

There are side effects associated with almost all therapies. One of the added benefits of tamoxifen is that is can reduce the risk of osteoporosis. In many women, tamoxifen causes many symptoms of menopause including hot flashes, vaginal discharge and mood swings. Tamoxifen has 2 rare but more serious side effects. These are a slight increased risk of developing cancer of the lining of the uterus (endometrial cancer) and uterine sarcoma, and a slightly higher chance of developing blood clots. For most women with breast cancer, the benefits of taking the drug far outweigh these risks.


Toremifene is another anti-estrogen closely related to tamoxifen. It may be an option for postmenopausal women with metastatic breast cancer.


Fulvestrant is a newer drug that reduces the number of estrogen receptors. It is often effective even if the breast cancer is no longer responding to tamoxifen. Hot flashes, mild nausea and fatigue are the major side effects.

For more information about breast cancer treatment and prevention at Fox Chase Cancer Center or to make an appointment, call 1-888-FOX CHASE (1-888-369-2427). The breast cancer scheduling department can be reached at 215-728-3001.

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