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Osteoporosis Drug Raloxifene as Effective as Tamoxifen
for Invasive Breast Cancer
Results of a new study show that the drug raloxifene, currently used to prevent
and treat osteoporosis in postmenopausal women, works as well as tamoxifen at
reducing breast cancer rates in postmenopausal women at increased risk of the
disease. Both drugs reduced the risk of developing invasive breast cancer by
about half.
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Tamoxifen and raloxifene were compared in a breast
cancer prevention trial.
Photo courtesy of NIH’s National Cancer Institute. |
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In 1998, the landmark Breast Cancer Prevention Trial showed that tamoxifen could
reduce the risk of invasive breast cancer in premenopausal and postmenopausal
women by nearly 50%. Raloxifene is a drug approved by the Food and Drug Administration
(FDA) for preventing osteoporosis in postmenopausal women. In animal studies,
it reduced the incidence of breast and uterine cancer. In preliminary human trials,
it reduced the risk of breast cancer without the uterine changes tamoxifen brings
that can lead to uterine cancer.
The Study of Tamoxifen and Raloxifene (STAR), one of the largest breast cancer
prevention clinical trials ever conducted, was sponsored by NIH’s National
Cancer Institute (NCI) to compare the two drugs. Researchers randomly assigned
19,747 postmenopausal women who were at increased risk for breast cancer to receive
either raloxifene (Evista ®) or tamoxifen (Nolvadex ®) daily for five
years. The maker of raloxifene, Eli Lilly and Company, and the maker of tamoxifen,
AstraZeneca Pharmaceuticals, provided their drugs and matching placebos without
charge. Eli Lilly also gave support to defray recruitment costs at the participating
centers and to help local investigators conduct the study.
The results were published in a pair of early release articles posted online
June 5, 2006 by the Journal of the American Medical Association. The
numbers of invasive breast cancers in both groups of women were statistically
the same: Among the 9,745 women in the raloxifene group, 168 developed invasive
breast cancer, compared to 163 of 9,726 women in the tamoxifen group. Those taking
raloxifene had fewer uterine cancers, but the difference wasn’t large enough
to prove it wasn’t due to chance. There were no significant differences
in noninvasive breast cancer, strokes, heart attacks and bone fractures. The
researchers also found little difference in the total number of deaths or in
the causes of death.
Raloxifene did have some advantages. Women taking it had a 21% lower rate of
cataracts and an 18% lower rate of cataract surgery. They also had a 30% lower
risk of pulmonary embolism and deep vein thrombosis, a clot in the deep veins
of the leg that leads to embolism (141 vs. 100). On the other hand, those taking
tamoxifen had a lower rate of noninvasive breast cancer (57 vs. 80), but that
difference wasn’t large enough to be judged statistically significant.
Quality of life measurements were similar for both drugs. Their side effects
varied, but were mild to moderate. The women taking tamoxifen, however, reported
higher levels of sexual interest, arousal and the ability to enjoy sex.
The STAR researchers will continue to follow up on the women in the study.
In the meantime, it’s important to note that raloxifene hasn’t yet
been approved by the FDA for use in preventing breast cancer. Talk to your doctor
about your options.
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