Longer-Term Data Confirm Raloxifene Reduces the Risk of Breast Cancer in Older Women
Keywords
Breast cancer, prevention, raloxifene (Evista®). (Definitions of many terms related to cancer can be found in the Cancer.gov Dictionary.)
Summary
Raloxifene (Evista®) substantially reduced the risk of invasive breast cancer in postmenopausal women with osteoporosis who took the drug for eight years. These long-term results confirm earlier findings in this same group women. It is not clear whether all women at risk for breast cancer would receive a similar protective benefit.
Source
American Society of Clinical Oncology (ASCO) annual meeting, New Orleans, June 6, 2004.
Background
Raloxifene was originally developed to prevent and treat osteoporosis and is now approved for that purpose by the U.S. Food and Drug Administration. But some research has shown that the drug also reduces the risk of breast cancer. In the Multiple Outcomes of Raloxifene (MORE) trial, the drug lowered breast cancer incidence by 72 percent over four years, compared to a placebo. The current trial, called CORE (Continuing Outcomes Relevant to Evista), continued to compare the standard 60 milligram dose of raloxifene to a placebo in women who took part in the MORE trial, following them for an additional four years.
Raloxifene belongs to a class of drugs called selective estrogen receptor modifiers or SERMs. Some breast cancer cells grow in response to estrogen. SERMS reduce the risk of breast cancer by blocking estrogen receptors in breast cells.
The Study
The participants in this study had all participated in the MORE trial and continued to receive the same treatment - either daily raloxifene (3,510 women) or a placebo (1,703 women). All participants were postmenopausal women with osteoporosis.
The study was led by Silvana Martino, D.O., of the Cancer Institute Medical Group and John Wayne Cancer Institute in Santa Monica, Calif.
Results
The women who took raloxifene had a 59 percent lower risk of breast cancer after four years on the CORE trial compared to those taking the placebo. Over the eight years of MORE and CORE together, the reduction in risk was 66 percent. Raloxifene was especially effective in women with breast tumors that were sensitive to estrogen (that is, with so-called estrogen-positive breast tumors). Among those taking raloxifene, 0.7 percent developed invasive breast cancer during CORE, compared to 1.6 percent of those on placebo.
The only serious side effect of raloxifene after eight years was an increased risk of blood clots in veins and in the lungs. There was no increased risk of stroke or heart attack with raloxifene.
Limitations
Because the study included only postmenopausal women with osteoporosis, it is not clear whether the results will hold true for other women.
Comment
Martino said it is still premature to recommend that postmenopausal women take raloxifene outside of a clinical trial to reduce their risk of breast cancer. She noted that two large trials with raloxifene are now underway: the STAR trial, which is comparing raloxifene to tamoxifen in the prevention of breast cancer, and the RUTH trial, which is comparing raloxifene to a placebo to prevent breast cancer and heart problems.
The results of these trials are expected in the next few years, she said, and should provide a more conclusive answer to the question of whether or not postmenopausal women at high risk for breast cancer would benefit from raloxifene.
Regarding the risk of blood clots, Martino said that this side effect, though serious, was quite rare. “Overall the drug is quite safe to take,” she said.
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