TUESDAY, Nov. 30, 2004 (HealthDayNews) -- If you're taking raloxifene (Evista) because you have osteoporosis, a new study finds a probable added benefit: The drug may also significantly reduce your risk of developing breast cancer.
The study, which appears in the Dec. 1 issue of the Journal of the National Cancer Institute, found that women taking raloxifene for eight years had a 59 percent lower risk of invasive breast cancer and a 66 percent lower risk of developing estrogen-receptor positive breast cancer, than women who had taken a placebo.
"These data demonstrate that the incidence of ER-positive invasive breast cancer continues to be reduced through eight years of raloxifene treatment in postmenopausal women with osteoporosis," wrote the authors of the study.
The caveat, according to Dr. Powel Brown, one of the authors of an editorial about the study, is that this study addresses only postmenopausal women with osteoporosis.
"Raloxifene is an option for breast cancer risk reduction for a specific group of women," said Brown, an associate professor of medicine at Baylor College of Medicine. "It is not for everyone."
More than 200,000 women are diagnosed with breast cancer every year, according to the American Cancer Society (ACS). The ACS estimates that a woman's lifetime risk of developing invasive breast cancer is one in seven. Estrogen-receptor positive breast cancers are fueled by the hormone estrogen. Raloxifene and tamoxifen, another drug used to reduce breast cancer risk, work as anti-estrogens in breast tissue.
The current study is a continuation of the Multiple Outcomes of Raloxifene Evaluation (MORE) trial. It sought to assess raloxifene's effectiveness in treating osteoporosis and, as a secondary measure, how effective it was in reducing breast cancer risk. That trial lasted four years and found that the incidence of breast cancer was 72 percent lower in women taking raloxifene than it was in women taking a placebo.
Called Continuing Outcomes Relevant to Evista (CORE), the current study was designed to see if the reduction in the incidence of breast cancer continued to be significantly lower after another four years of treatment.
Just over 3,500 women who had randomly been assigned to take raloxifene in the first trial continued taking the drug (60 mg daily), while 1,703 women who had been assigned to the placebo group continued to take a placebo for up to an additional four years.
All of the women were postmenopausal and had osteoporosis.
Over the four years of the CORE trial, the incidence of invasive breast cancer was 59 percent lower and the rate of estrogen-receptor positive breast cancer was 66 percent lower for women who took raloxifene than for women taking the dummy drug.
Overall, the eight-year incidence of invasive breast cancer (combined results from MORE and CORE) was 66 percent lower for women who were on raloxifene therapy. The incidence of estrogen-receptor positive breast cancer was down by 76 percent for women taking raloxifene compared to placebo over the eight years for both studies.
Raloxifene's most troubling side effect -- an increased risk of blood clots -- remained stable, at about 2 percent, throughout both studies.
The study was funded by Eli Lilly and Co., the maker of Evista. It has eight named authors, all of whom have connections to the company; some received grants or speaking fees, some are stockholders, and three are Lilly employees.
"On the surface, the results of this study sound great," said Brown. But, he and the other authors of the editorial expressed some concerns about its design. First, the women who were enrolled in MORE were asked to continue in the study. Those who dropped out may have done so because they experienced side effects.
Also, while the women were randomized in the MORE trial, they were not in the CORE trial. They simply continued in the group they had originally been assigned. There was also a varying time gap between when the women finished the MORE trial and then began the CORE trial; for some women that gap was as long as five years. That meant some women were off the drug for a long time before they began taking it again. Additionally, the dose of raloxifene in the CORE trial was half what it was in the MORE trial.
Despite those reservations, Brown said, "One can say continued treatment with raloxifene is associated with a reduced incidence of breast cancer in women with osteoporosis."
Dr. Jay Brooks, chief of hematology/oncology at the Ochsner Clinic Foundation Hospital in Baton Rouge, La., pointed out that women with osteoporosis may already have a reduced risk of breast cancer.
"People who are heavier, who have very dense bones, have a higher risk of developing breast cancer," he said, so women with osteoporosis who are often slim may have a lower risk of getting breast cancer to begin with.
Brown said that for the prevention of breast cancer in women who are at high risk for the disease, treatment with tamoxifen is still the "gold standard." Brooks agreed.
Both indicated that a large, ongoing trial is comparing the use of tamoxifen and raloxifene for breast cancer prevention to see which drug is more effective. Brown said those results are due in early 2006.
In the meantime, Brooks suggested that if a woman is concerned about developing breast cancer, losing weight could reduce her risk.
"The evidence is clear: Obesity clearly increased the risk of breast cancer, and it also increases the risk of recurrence," he said.
To learn more about raloxifene, visit the National Library of Medicine.