Women Have Small Increased Cancer Risk Three Years After Ending HRT, Study Finds

Women taking combination hormone replacement therapy have a slightly increased risk of cancer three years after ending treatment, but initial increases in cardiovascular risks appear to fade, according to a follow-up study published in the Journal of the American Medical Association Wednesday, the Wall Street Journal reports (Corbett Dooren, Wall Street Journal, 3/5). The study also found that improved bone health and increased risks of blood clots, stroke and heart attack seen among some HRT users fell to normal rates after women stopped taking the drugs.

For the study, researchers led by Gerardo Heiss at the University of North Carolina-Chapel Hill analyzed an earlier NIH-sponsored Women's Health Initiative study (Parker-Pope, New York Times, 3/5). NIH researchers ended the WHI study of combination HRT in July 2002, three years earlier than scheduled, because they determined that the treatment might increase the risk for heart disease, invasive breast cancer and other health problems (Daily Women's Health Policy Report, 2/27).

The new analysis followed 15,730 postmenopausal women who participated in a WHI study. The researchers found 281 cancers among the women who received Wyeth's HRT Prempro, compared with 218 in the placebo group. The researchers also found 343 heart attacks, strokes and blood clots in the HRT group, compared with 323 in the placebo group, a statistically insignificant difference. The mortality rate from all causes was 15% higher among women taking Prempro than those taking a placebo, but the higher rate was not considered statistically significant, according to the study (Maugh, Los Angeles Times, 3/5).

The study found a 0.3% increased risk of cancer for each woman who took HRT, or about three additional cases annually per 1,000 women (New York Times, 3/5). The study also found a 27% higher risk of developing breast cancer among HRT users three years after halting treatment (Los Angeles Times, 3/5). Although breast cancer comprised the majority of cancer cases, the researchers also found a higher rate of other cancers, such as lung cancer, among HRT users.

It is unclear how long women have an increased cancer risk after ending HRT, Marcia Stefanick, a professor of medicine at the Stanford Prevention Research Center and senior author of the study, said. The new findings likely will encourage researchers to look into how HRT might increase the risk of cancers that have not previously been associated with the therapy, such as lung cancer, the Washington Post reports (Stein, Washington Post, 3/5). The study was funded by the National Heart, Lung and Blood Institute (Los Angeles Times, 3/5).

Reaction

According to the San Francisco Chronicle, the study reinforces some physicians' views that women should take the smallest possible dose of HRT for as little time as possible. Stefanick said she does not think the study's findings "should be frightening to women" but added that she thinks "women should only go on [HRT] if they have severe symptoms. They should really think about whether they're so bad off that they want to start something that comes with all these risks" (Allday, San Francisco Chronicle, 3/5). Heiss added that the study's findings are of "modest magnitude" and are "not something to be alarmed about, but it's something to be aware of."

Gary Stiles, chief medical officer at Wyeth, said the company does not believe the new study "provides any new guidance" (Wall Street Journal, 3/5). Peter Ravdin of the M.D. Anderson Cancer Center, who recently reported a nationwide decrease in new cancer cases, said the new analysis's findings could have happened by chance. "They just didn't have the statistical power to identify a decrease that we've seen in the population data," Ravdin said, adding, "All the epidemiological data argues against their results" (Washington Post, 3/5).

An abstract of the study is available online.

ABCNews.com on Tuesday reported on the study (McKenzie, ABCNews.com, 3/4). Video of the segment is available online. Expanded ABC News coverage also is available online.

NPR's "All Things Considered" on Tuesday also reported on the study. The segment includes comments from Heiss and JoAnn Manson, director of preventive medicine at Brigham and Women's Hospital (Neighmond, "All Things Considered," NPR, 3/4). Audio of the segment is available online.