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Medical Edge Newspaper Column from Mayo Clinic
NEW DRUG SHOWS PROMISE FOR BREAST-CANCER PREVENTION
DEAR MAYO CLINIC: Can you provide an update on the recent breast cancer prevention research that was in the news? — Thornhill, Ontario, Canada
ANSWER: You are probably referring to the National Cancer Institute’s Study of Tamoxifen and Raloxifene (STAR) Trial. The initial results were released in April 2006 and are important for anyone who is at high risk of developing breast cancer.
This large, four-year study — nearly 20,000 women participated — compared the effectiveness of drugs tamoxifen (Nolvadex) and raloxifene (Evista) in reducing breast cancer for postmenopausal women at increased risk of the disease. Results from a landmark 1998 study had already shown that tamoxifen reduced the risk of invasive breast cancer in premenopausal and postmenopausal women by about 50 percent.
STAR researchers found that raloxifene, a drug used to treat osteoporosis, was just as effective as tamoxifen in reducing the risk of developing invasive breast cancer in postmenopausal women.
Both tamoxifen and raloxifene are selective estrogen receptor modulators and work by blocking estrogen receptors found in the breast from binding to estrogen. Estrogen stimulates breast tissue and cell proliferation and has been implicated in the development of breast cancer.
STAR results also indicate that women taking raloxifene had fewer serious side effects than those taking tamoxifen. Uterine cancers, especially endometrial cancers, are a rare but serious side effect of tamoxifen. In the new study, women who took raloxifene had 36 percent fewer uterine cancers than women taking tamoxifen. Thirty-six of the 4,732 women who took tamoxifen developed uterine cancer compared to 23 of the 4,712 women who took raloxifene. (More than half of the women in STAR had had a hysterectomy and were not at risk of uterine cancer.)
Both tamoxifen and raloxifene are known to increase a woman’s risk of blood clots. In the study, women taking raloxifene had 29 percent fewer blood clots than women taking tamoxifen.
Also, initial STAR results suggest that raloxifene doesn’t increase the risk of developing a cataract, while tamoxifen does.
Tamoxifen, not raloxifene, reduced by half the risk of developing non-invasive breast tumors, which can be markers for an increased risk of developing invasive breast cancer.
For women who are postmenopausal and at increased risk of breast cancer, STAR results show that raloxifene is a promising alternative to tamoxifen. The Food and Drug Administration has not yet approved raloxifene for reducing breast cancer risk. However, the trial results are impressive and provide strong evidence to support the use of raloxifene for reducing the risk of breast cancer.
Women should consult with a physician to assess their degree of breast cancer risk; medical and family history and reproductive history, as well as a prior breast biopsy, are critically important in determining whether tamoxifen, raloxifene or other approaches are needed. Lifestyle changes can be part of a prevention strategy, too. Examples include limiting alcohol intake, avoiding postmenopausal obesity, being physically active and avoiding long-term hormone therapy.
— Sandhya Pruthi, M.D., Breast Diagnostic Clinic, Mayo Clinic, Rochester, Minn.
Additional Resources:
Breast Cancer
Appointment Information
More Information on Breast Cancer
Breast Cancer Prevention
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© 2006 TRIBUNE MEDIA SERVICES, INC.
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