Raloxifene for Breast Cancer Prevention: An NWHN Analysis
National Women’s Health Network: April 18, 2006
Yesterday, the National Cancer Institute (NCI) announced preliminary results from STAR, a large clinical trial comparing the effect of raloxifene and tamoxifen on risk of developing breast cancer in postmenopausal women who were considered to be at higher than average risk.
The trial was funded by the NCI and Eli Lilly, manufacturer of raloxifene, which is currently marketed under the brand name Evista for prevention and treatment of osteoporosis.
According to the NCI, both drugs cut the number of new cases of breast cancer in half, but women taking raloxifene experienced fewer serious side effects such as blood clots and cancer of the uterus. The NCI stressed this benefit in its announcement, stating “For many women, raloxifene’s benefits will outweigh its risks in a way that tamoxifen’s benefits do not.” National Women’s Health Network (NWHN) is more cautious about the results of the trial, and believes that the breast cancer benefit of raloxifene may only be useful to a very small number of women.
What do the numbers show?
The numbers announced by NCI show that raloxifene is somewhat better than tamoxifen (brand name Nolvadex), although not strikingly so. 23 women taking raloxifene developed uterine
cancer, compared with 36 women on tamoxifen; and 100 women taking raloxifene experienced serious blood clots, compared with 141 women on tamoxifen.
These results show that raloxifene is significantly less likely than tamoxifen to cause serious side effects - but we question whether it is likely to make a significant difference in women’s lives. Using the numbers released by NCI, we calculate that of the nearly 10,000 women who took raloxifene for up to five years, only about 30 benefited, once the serious risks are taken into account. While some women may appreciate this marginal
benefit, NWHN questions whether it should be viewed as a major advance in preventing breast cancer.
We must also remember that the results have not yet been reviewed by experts who weren’t involved in the study (a requirement before the research can be published in a major medical journal), nor has the Food and Drug Administration (FDA) examined the records of the study to determine whether the agency will approve raloxifene for breast cancer risk reduction.
Should women take raloxifene?
Women who are currently taking tamoxifen to reduce their risk of breast cancer should wait until the results of the STAR trial have been reviewed by the FDA before considering switching to raloxifene. FDA reviewers have access to all the information generated by the researchers and can provide an objective assessment of the results. Women who take bisphosphonates (drugs such as Fosamax, Actonel, Boniva) for osteoporosis also shouldn’t rush to switch. While there are still some questions about the long-term effects of bisphosphonates on bone structure, it seems clear that they do not increase the risk of
stroke, blood clots or cancer.
Healthy women who are not at higher than average risk of either breast cancer or osteoporosis should be especially skeptical of any efforts to persuade them to start taking raloxifene. It’s very likely that the ultimate results of the STAR trial will show that
raloxifene isn’t quite as bad as tamoxifen, but it’s still not safe enough for most women to use. And we’ve learned that it’s important to wait until enough information is available for women to be able to make truly informed choices.
NWHN urges women and their practitioners not to get caught up in the hype, and wait for the facts.
To read the National Women’s Health Network’s full analysis of the STAR trial, visit: http://www.nwhn.org/alerts/alerts_details.php?aid=63
