Reduce Risk of Breast Cancer
Posted by medconsumers on May 1, 2006
Drugs to Reduce Breast Cancer Risk: Is It Worth It?
Initial results from a government-sponsored study indicate that the osteoporosis drug raloxifene (brand name: Evista) may protect against breast cancer. The study compared it against an older anti-breast cancer drug, tamoxifen (brand name: Nolvadex), and found both are equally good at reducing the chances of developing breast cancer. Some media reports of this study were overly enthusiastic about its finding.
The study is yet to be published and therefore has not been peer-reviewed. If the results hold up, Eli Lilly, maker of raloxifene, will be able to apply to the FDA for permission to promote raloxifene as a breast cancer preventive. Expect an overheated advertising campaign by Lilly touting raloxifene as a “two-for”—a drug that will save women from osteoporosis AND breast cancer.
Raloxifene has been on the market since 1997. It is good at increasing bone density; completely ineffective at reducing the most serious type of fracture (hip); and minimally effective in reducing spinal fractures. Spinal fractures can cause pain and a dowager’s hump in advanced age, but many are entirely symptomless. Tamoxifen has been on the market since 1972. First as an adjunctive treatment for breast cancer and more recently (1998) as a preventive drug for healthy but high-risk women. It never took off for the latter purpose because, according to one report, many doctors were uneasy about prescribing a cancer drug to healthy women every day for five years.
Both raloxifene and tamoxifen are what is called selective estrogen receptor modulators, or SERMs, which means that they protect the breast from estrogen’s cancer-causing potential but preserve estrogen’s protective effect on the bones. This is why SERMS were initially promoted as designer estrogens.
The National Cancer Institute sponsored the new study that compared the two drugs called the STAR trial, short for Study of Tamoxifen and Raloxifene, and the initial results were posted last month on its Web site (www.cancer.gov see initial results STAR). The STAR trial included postmenopausal women at high risk for breast cancer who had been randomly assigned to take one or the other drug. The NCI hailed both drugs as having reduced the incidence of breast cancer by 50%, which was uncritically picked up by most of the media.
Here’s what the NCI should have explained: Of the 9,700-plus women in each drug group, about 165 got breast cancer. This translates to 1.7%; whereas, 3.4% would be expected to develop breast cancer had they not taken a drug. (Hence the 50% reduction in breast cancer incidence.) Another way of saying the same thing is: 98.3% of high-risk women will not get cancer if they take raloxifene or tamoxifen; whereas, if they take no drug, 96.6% of women will not get cancer. Obviously, much more research is needed to determine who is at high risk for breast cancer.
If you are thinking of taking raloxifene every day for five years, consider the following:
It is premature to call raloxifene and tamoxifen preventive drugs. The STAR lasted only four years and breast cancer can take from 12 to 17 years to develop. Therefore, it is not known whether these drugs prevent breast cancer or merely delay its onset. The Tamoxifen Breast Cancer Prevention Trial lasted nearly five years.
The media reports of STAR emphasized fewer adverse reactions for raloxifene. However the 29% fewer blood clots and 36% fewer uterine cancers are not considered to be statistically significant because these conditions are rare. (Findings could have occurred by chance.) However, the finding of fewer cataracts in the raloxifene users is statistically significant. There were fewer cases of noninvasive breast cancer (e.g., ductal carcinoma in site, which does not always become life-threatening if left undetected.) in the women taking tamoxifen. [Note: When the STAR results were reported at a June meeting of the American Society of Clinical Oncology and published simultaneously online in the Journal of the American Medical Association, there was no overall difference between the two drugs in the study participants’ self-reported side effects—with some exceptions. Hot flashes, vaginal bleeding, bladder control problems were more common in women on tamoxifen. And pain during sexual intercourse and joint pain were more common in those on raloxifene.]
Raloxifene’s spinal fracture reduction benefit is small. Three-year results of a major trial showed spinal fractures in 10.1% of the women on placebos; in 6.6% of women on 60-mg/daily of raloxifene; and in 5.4% for women on 120 mg/daily of raloxifene.
Less is known about the long-term effects of raloxifene than is known about tamoxifen. It took more than 25 years of tamoxifen use before a rare life-threatening adverse effect (endometrial sarcoma) became apparent.
Maryann Napoli, Center for Medical Consumers ©May 2006
For another perspective on this study, see Breast Cancer Action’s Newsletter