MEDICATIONS: UPDATED ANALYSIS OF WHI ESTROGEN-ONLY DATA OFFERS POSITIVE NEWS

April 14, 2006 — A new study provides good news for women who've had a hysterectomy and take estrogen to alleviate their menopausal symptoms. Using data from the Women's Health Initiative (WHI) estrogen-alone trial, researchers report that, after seven years of follow-up, conjugated equine estrogens used alone did not increase breast cancer incidence in postmenopausal women who had had their uterus removed.

The findings in the April 12 issue of the Journal of the American Medical Association are in sharp contrast to results of the combined hormone therapy (estrogen plus progestin) arm of the WHI, which was halted in 2002 after showing a significant increase in breast cancer, as well as heart attack, stroke, and blood clots. The estrogen-alone trial was stopped in March 2004 because of an increased risk of stroke. However, further analysis was conducted after the preliminary data showed fewer breast cancers in women taking estrogen alone compared with women taking a placebo. The data seemed to contradict previous epidemiological evidence that associated exogenous estrogens with breast cancer.

"This should be reassuring to women who have had hysterectomies and want to use hormone therapy for menopausal symptoms but have been wary because they are afraid estrogen will increase their risk of breast cancer," says Isaac Schiff, M.D., chair of ACOG's Task Force on Hormone Therapy. "Some previous studies have associated estrogen with increased breast cancer incidence, and when the estrogen-plus-progestin arm of the WHI was halted, many suspected that it was the estrogen that led to the increased breast cancer risk. These new findings appear to show otherwise."

In the JAMA study, women taking estrogen-alone were more likely to have abnormal mammograms that required follow-up. Dr. Schiff noted that estrogen tends to make breast tissue denser and can make mammograms harder to read. The percentage of abnormal mammograms after the first year among the women taking estrogen was 9.2 percent compared with 5.5 percent among the women taking a placebo. At the end of the seven years, the cumulative percentage of abnormal mammograms in the estrogen group was 36.2 percent compared with 28.1 percent in the placebo group.

"Estrogen-alone hormone therapy is not for women who have a uterus because of the increased risk of uterine cancer," Dr. Schiff says. "But for women who have had a hysterectomy and are suffering from vasomotor symptoms, such as hot flashes and night sweats, estrogen may be a solution. These women are often the most symptomatic because when a woman has her uterus removed, she often has her ovaries removed, which may cause her to suffer more symptoms."

Dr. Schiff noted that while estrogen remains one of the best remedies for women suffering from vasomotor symptoms, it doesn't come without risks. Each woman should discuss with her doctor the risks and benefits of hormone therapy and her individual and family history. Women should take the lowest possible dose to relieve symptoms, use hormone therapy for the shortest period of time, and reevaluate the need for hormone therapy each year with their doctor.