WESTPORT, Jun 16 (Reuters Health) - Forty months of data show that raloxifene used to treat osteoporosis in postmenopausal women reduces risk of invasive breast cancer by 76%. The findings, from the Multiple Outcomes of Raloxifene Evaluation (MORE) trial, are published in today's issue of The Journal of the American Medical Association.
Women in the trial, all younger than 81 years of age and all with a vertebral fracture or a femoral neck or spine score that was more than 2.5 standard deviations below normal at enrollment, were randomized to receive either 60 mg or 120 mg raloxifene daily or placebo. Principal investigator Dr. Steven R. Cummings of the University of California at San Francisco commented in an interview with Reuters health that the dosage that the women received "...didn't really matter. They got the same effect [with both dosages]."
Raloxifene decreased risk of estrogen receptor-positive breast cancer by 90% but did not decreased estrogen receptor-negative breast cancer risk. Raloxifene tripled the risk of thromboembolic disease but did not significantly increase the risk of endometrial cancer (relative risk 0.8). In contrast. tamoxifen has been shown to quadruple the risk of endometrial cancer, Dr. Cummings noted.
Dr. Cummings expressed excitement over the findings. "You don't often find changes of this magnitude in medicine," he said. "If this reduced risk continues over 10 years--currently there is a one in nine chance of a woman getting breast cancer--we could reduce the risk to 2 or 3 out of 100 over the course of life."
"The issue is, how long do these effects last?" Dr. Cummings continued. "We're not yet ready to prescribe raloxifene for all postmenopausal women. For those at risk of breast cancer and osteoporosis, or for whom these diseases are a source of worry, [treatment should be considered]."
Dr. Cummings pointed out that estrogen receptor-negative breast cancers are far more common in younger women than in postmenopausal women and that raloxifene did not reduce risk of these cancers. Raloxifene and tamoxifen "...may offer less for these women."
In an editorial, Dr. Adele L. Franks of the Prudential Center for Health Care Research in Atlanta and Dr. Karen K. Steinberg of the Centers for Disease Control and Prevention in Atlanta reiterate that raloxifene is not yet recommended for all postmenopausal women. But the authors add that "...[in] seeking to create the perfect [selective estrogen receptor modulator] that will duplicate or improve the beneficial effects of estrogen while protecting against its risks, the raloxifene findings provide solid encouragement."