LOS ANGELES -- Researchers at the University of California San Francisco report that a novel hormone therapy drug reduces the risk of breast cancer in women by 70 percent.

"Our findings are very exciting because they show that it may be possible to prevent breast cancer in postmenopausal women who have no prior history of the disease," says Steven Cummings, MD, UCSF professor of medicine and epidemiology and lead author of the study.

Cummings presented his findings today (May 18) at the annual meeting of the American Society of Clinical Oncology.

UCSF researchers found that the osteoporosis prevention drug, raloxifene, drastically reduced the risk of breast cancer in postmenopausal women without indicating an increased risk of endometrial, or uterine cancer. Other drugs in raloxifene's class, including tamoxifen, have been shown to increase the risk of endometrial cancer in women.

Although tamoxifen was recently reported to reduce the risk of breast cancer in women who are at high risk of the disease by 45 percent, it also showed an increased risk of endometrial cancer. Of the 13,388 women who participated in the tamoxifen study, 33 of those who received the drug developed endometrial cancer, compared to 14 of the women assigned to placebo. Raloxifene and tamoxifen belong to a class of drugs called selective estrogen receptor modulators (SERMS), which block the actions of estrogen in some tissues, such as the breasts, and mimic estrogen in other tissues, such as the bones.

"During the clinical trials of raloxifene, we saw twice as many cases of breast cancer develop among women taking placebo compared to those taking raloxifene," Cummings says.

After an average of 33 months, 32 cases of breast cancer developed in the women who participated in the study. While 21 or .82 percent of the women who were given placebo developed breast cancer, only 11 or .21 percent of those assigned to raloxifene developed the disease. However, like tamoxif
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Contact: Abby Sinnott
sinnott@itsa.ucsf.edu
(415) 885-7277
University of California - San Francisco
18-May-1998