MONDAY, April 17, 2006 (HealthDay News) -- The osteoporosis drug raloxifene equals tamoxifen in reducing breast cancer risk in high-risk postmenopausal women, but with fewer side effects, a new study shows.
"We believe that raloxifene is the winner of this trial," said Dr. Lawrence Wickerham, associate chairman of the U.S. National Surgical and Adjuvant Breast and Bowel Project and protocol officer for the trial, at a news conference Monday.
The results will likely signal a shift in clinical practice for the use of raloxifene, whose brand name is Evista.
"This is good news for women," Dr. Leslie Ford, associate director for clinical research in the division of cancer prevention at the U.S. National Cancer Institute, said at the same news conference. "We think that this gives women a real choice for addressing two of the leading causes of morbidity and mortality as they age -- breast cancer and fractures."
"We now have two medicines that can be given to high-risk women to decrease their chances of developing breast cancer," added Dr. Jay Brooks, chairman of hematology/oncology at Ochsner Health System in Baton Rouge, La. "Evista is as good as tamoxifen in preventing invasive breast cancer and it has fewer side effects. I think we'll see a shift over to the use of Evista in this setting." Ochsner had about 100 women participating in the trial.
Additional data from the Study of Tamoxifen and Raloxifene (STAR) trial will be presented in June at the annual meeting of the American Society of Clinical Oncology in Atlanta.
The U.S. Food and Drug Administration approved tamoxifen in 1998 to reduce the risk of breast cancer in women at high risk for the disease.
"This was a major step in our battle against breast cancer. However, even with cutting breast cancer risk in half, it got little use because of the rare but serious side effects that we knew occurred," Ford said.
The current STAR trial, initiated in 1999 and involving almost 20,000 women, is one of the largest breast-cancer prevention clinical trials ever conducted.
Participants, all of whom were postmenopausal and at heightened risk for breast cancer, were randomly assigned to receive either 60 milligrams of raloxifene or 20 mg of tamoxifen daily for about four years.
Drug maker AstraZeneca provided the tamoxifen for the trial while another pharmaceutical company, Eli Lilly, provided the raloxifene, both free of charge.
Both drugs reduced the risk of developing invasive breast cancer by about 50 percent, the researchers reported.
Women taking raloxifene had 36 percent fewer uterine cancers and 29 percent fewer blood clots than the women taking tamoxifen. The risk of stroke, heart attack and bone fracture was equivalent in each group. Raloxifene did not increase the risk of developing a cataract, as tamoxifen does, the study found.
While tamoxifen has previously been shown to reduce by half the incidence of "in situ" -- or noninvasive breast cancers -- raloxifene did not show a similar effect.
"There's an important caveat," Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society, said in a prepared statement. "Taking away the risk of increased uterine cancer and blood clots from tamoxifen comes at a price: the loss of the protective effect of tamoxifen to potentially prevent these non-invasive breast cancers. As a result, the outcome of the study is not as clear-cut as we might have hoped for."
Raloxifene is currently approved only to prevent or treat osteoporosis; an estimated half a million postmenopausal American women are taking the drug for this use. Ford speculated that Eli Lilly will be asking the FDA for an additional "indication," or approval of the drug.
Tamoxifen remains the only drug currently approved for breast cancer risk-reduction in pre-menopausal women, said Dr. Victor Vogel, STAR protocol chairman. "We anticipate that if Lilly gets approval, the indication will only be for postmenopausal women, so tamoxifen will remain the drug of choice for reducing risk in pre-menopausal women," he said.
Trial participants who were taking raloxifene will continue to get the drug until they have completed five years of treatment. Women in the tamoxifen arm can choose to continue to take tamoxifen or to get raloxifene instead.
The bottom line, Brooks said, is to make sure women understand that there are options for reducing breast cancer risk.
"We can predict which women are at a high risk for developing the disease and we can do something about that and not enough women and physicians understand that," he said.
More information
For more on the STAR trial, head to the U.S. National Cancer Institute.
