Breast Cancer Risk Lingered Years after Women Discontinued Estrogen-Progestin Therapy, Stanford Researcher Says

STANFORD, Calif.--(BUSINESS WIRE)--Mar 4, 2008 - A follow-up study of postmenopausal women who took the combination of estrogen and progestin for more than five years as part of the landmark Women's Health Initiative shows that the women continued to face an increased risk for breast cancer nearly three years after they quit taking the hormones.

The new study also shows that while some of the other health risks and benefits diminished after the women had stopped taking the estrogen-progestin combination, the overall health risk was 12 percent higher at the end of eight years (with women on the pills for an average of 5.6 years and then off for 2.4 years) compared with those who took placebos. This was largely due to the high risks of breast cancer, strokes and serious blood clots during the original trial while the women took the hormones.

The Stanford University School of Medicine researcher who is the senior author of the follow-up study said the results indicate that the potential harms from estrogen-progestin therapy still outweigh the benefits, and that women should continue to be cautious in deciding whether to take the hormones to relieve menopausal symptoms.

"Menopausal women really need to think through whether using estrogen-progestin is the right thing to do, particularly if continued for more than a few years," said Marcia Stefanick, PhD, professor of medicine at the Stanford Prevention Research Center, noting that the breast-cancer risks apply only to women who take the combination therapy, and not those who take estrogen alone. A different portion of the WHI study showed that estrogen-only therapy doesn't increase the risk of breast cancer.

The follow-up study will be published in the March 5 issue of the Journal of the American Medical Association.

The WHI is the largest-ever study to examine the health of postmenopausal women ages 50-79. One of its best-known components involved hormone therapy. There were two arms of the hormone therapy study: one for women who had undergone hysterectomies and who were randomly assigned to take either estrogen or placebo, and the other for women who still had a uterus and who took either estrogen-progestin or placebo.

Stefanick was the chair of the WHI steering committee for the duration of the original trial. She is now chair of the WHI Extension Study, which will continue to follow participants through at least 2010.

In 2002, researchers abruptly halted the estrogen-progestin arm of the trial, which involved 16,608 women, when evidence showed that women who had taken the hormones for an average of 5.6 years had a 26 percent higher risk for breast cancer than those in the placebo group. Additionally, they had a greater risk of stroke, blood clots and, in the first year of treatment, heart attack. However, the women taking the hormones also had a lower risk for bone fractures and colon cancer.

In the new follow-up study, which tracked 15,730 of the original participants for an average of 2.4 years after the trial ended, the risk of developing breast cancer was 27 percent higher during the follow-up period, with 79 of the women who took the hormones developing invasive breast cancer compared with 60 of the women who took the placebo. Additionally, the risks of developing any type of cancer was 24 percent higher, with 281 women developing cancer in the post-treatment group compared with 218 women in the placebo group.

Stefanick said the follow-up study also contained potentially important findings that didn't reach statistical significance, meaning they could be due to chance, but that may be resolved after continuing to track the women's health. For instance, during the 2.4-year follow-up period there were 15 percent more deaths from all causes among the women who previously took the combined hormones, compared to those who had taken placebo pills.

Also, largely because there were more occurrences of cancer during the follow-up period, the global risk index (a measure of a variety of health outcomes, including deaths) continued to be 11 percent higher after women stopped taking the hormones. Stefanick said a likely reason that the finding didn't reach statistical significance is that most of the cardiovascular risks that arose during the trial diminished after women stopped taking the hormones, as did the benefits of fewer fractures and reduced rates of colorectal cancer.

Nonetheless, Stefanick said the higher risk for breast cancer "appears to continue for women who took estrogen and progestin, even years after stopping the hormones."

Both the estrogen-alone and estrogen-progestin studies turned the conventional wisdom about hormone therapy on its head. For many years, observational studies and other evidence indicated that in addition to relieving menopausal symptoms, hormone therapy helped protect women against heart disease and bolstered their overall health. However, neither trial showed any benefit in preventing heart disease, and both trials showed hormone therapy, while having some benefits, posed substantial health risks. The estrogen-only arm of the study was stopped in 2004, one year before its scheduled conclusion, because of concerns that estrogen increased the risk of stroke and blood clots without providing any protection against heart disease.

Since the results of those trials were announced, the use of hormone therapy has dropped dramatically. Current health guidelines recommend that women seeking relief from menopausal symptoms use the lowest hormone dose necessary and that they limit the duration of the therapy.

"Women are being told to use hormones for 'the shortest time possible,' but we can't really define what 'short' means," Stefanick said. "Clearly, taking estrogen and progestin for 5.6 years is too long because the risk for breast cancer continued to be elevated after the women stopped taking the hormones and remained significant, compared to placebo, after stopping the hormones for 2.4 years."

She encouraged women who are experiencing menopausal symptoms to consider non-estrogen alternatives to manage hot flashes and other discomforts, to consult with their physicians as to the possible use of hormone therapy and to make dietary and lifestyle changes, particularly increasing their physical activity, to reduce their risks for chronic diseases.

Stefanick's co-authors include several WHI investigators from throughout the country; the lead author is Gerardo Heiss, MD, PhD, professor of epidemiology at the University of North Carolina-Chapel Hill.

Both the original WHI study and the follow-up study were funded by the National Heart, Lung and Blood Institute.

Stanford University Medical Center integrates research, medical education and patient care at its three institutions -- Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital at Stanford. For more information, please visit the Web site of the medical center's Office of Communication & Public Affairs at http://mednews.stanford.edu.

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