The hormonal therapy medicines tamoxifen and Evista (chemical name: raloxifene) are approved by the U.S. Food and Drug Administration to be used to reduce breast cancer risk in postmenopausal women at higher-than-average risk. New guidelines from the American Society of Clinical Oncology (ASCO) also recommend both of these medicines to reduce risk in postmenopausal women at high risk.
ASCO is the world's largest organization of cancer doctors and researchers. ASCO guidelines give doctors recommendations for treatments that are supported by much credible research and experience. ASCO guidelines released in 2002 recommended only tamoxifen to lower breast cancer risk in high-risk, postmenopausal women. After those guidelines were put out, four large studies showed that Evista also effectively lowers breast cancer risk in high-risk, postmenopausal women. Based on this research, the ASCO guidelines have been updated to include both Evista and tamoxifen as recommended treatments to lower risk in high-risk, postmenopausal women.
Both tamoxifen and Evista are selective estrogen receptor modulators (SERMs). SERMs can lower the risk of hormone-receptor-positive breast cancer in postmenopausal women AND improve bone health. SERMs block the action of estrogen in breast cells and certain other cells in the body by sitting in the cells' estrogen receptors. SERMs don't affect all estrogen receptors the same way because they're selective (as the name says). While tamoxifen blocks estrogen's action on breast cells, it activates estrogen's action in bone and liver cells, so tamoxifen also can help stop bone loss after menopause and help lower cholesterol. Hormone-receptor-negative breast cancers don't have estrogen receptors, so they aren't affected by SERMs. Neither tamoxifen nor Evista lowers the risk of hormone-receptor-negative breast cancer.
Both tamoxifen and Evista are pills taken by mouth and each is taken for 5 years to reduce breast cancer risk in high-risk, postmenopausal women. Evista also is approved to strengthen bones and reduce the risk of osteoporosis in postmenopausal women, regardless of breast cancer risk. So the new ASCO guidelines say that Evista -- but not tamoxifen -- can be taken for more than 5 years by postmenopausal women with osteoporosis and a higher-than-average risk of breast cancer.
Because tamoxifen and Evista work in the same way, they have the same possible treatment risks and side effects, including:
- hot flashes
- joint pain
- leg cramps
- flu-like symptoms
- blood clots deep in the legs
- a blood clot that travels to the lungs (called a pulmonary embolism)
The likelihood or severity of any side effect seems to be different with each medicine. In one study women taking tamoxifen were more likely than women taking Evista to have bothersome hot flashes and sweating, while women taking Evista were more likely to have joint pain.
Because of the risk of potentially life-threatening blood clots, tamoxifen and Evista are NOT recommended for women who have had a serious blood clot or are at high risk for blood clots.
If you're a postmenopausal woman and believe your breast cancer risk is higher than average, talk to your doctor about your risk and about steps you can take to lower that risk. Your doctor can help you assess your breast cancer risk. Then you and your doctor can decide if medicine to lower your risk is appropriate for you and your unique situation. You and your doctor may use the National Cancer Institute's risk calculator tool. This online tool uses your personal and family medical history to objectively assess your breast cancer risk.
If lowering your risk with medicine is a good option for you, the new ASCO guidelines give you and your doctor confidence in choosing either tamoxifen or Evista. Which one you choose will depend on a number of factors, including possible side effects, your bone health, and other aspects of your medical history. Together, you and your doctor can choose the risk-lowering medicine that makes the most sense for you.
Editor's Note: In July 2013, the American Society of Clinical Oncology put out new guidelines on using hormonal therapy medicines to reduce breast cancer risk in high-risk undiagnosed women. Besides tamoxifen and Evista, the guidelines also recommend that doctors talk to postmenopausal high-risk women about using the aromatase inhibitor Aromasin (chemical name: exemestane) to reduce risk.