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NCI scientists followed 44,241 women for about 20 years. The women were former participants in the Breast Cancer Detection Demonstration Project, a mammography screening program conducted between 1973 and 1980.
In the 1940s, women began using estrogens in high doses to counteract some of the discomforts of menopause such as hot flashes and vaginal dryness. After it became clear in the 1970s that women who took estrogen alone had
a six to eight times higher risk of developing cancer of the lining of the uterus (endometrial cancer), doctors began prescribing progestin along with much lower doses of estrogen, which countered the endometrial cancer risk. Estrogens alone were limited to women who had undergone a hysterectomy.
Women in the 2002 study who took combination estrogen-progestin therapy were not at increased risk for ovarian cancer. However, says study author James V. Lacey, Jr., Ph.D., of NCI's Division of Cancer Epidemiology and Genetics, "there simply aren't enough data to say whether taking the combined therapy has an effect on ovarian cancer."
These data were published in conjunction with results of a large, multi-center clinical trial of the Women's Health Initiative, which showed increases in breast cancer, coronary heart disease, stroke, and blood clots in the lungs and legs for women who took combination estrogen-progestin therapy for an average of 5.2 years. Risk for hip factures and colon cancer decreased. Because the overall harm was greater than the benefit, that trial was stopped 3 years ahead of schedule.
Since these studies were published in 2002, use of menopausal hormone therapy among U.S. women has dropped dramatically, according to a study published
in January 2004 in the Journal of the American Medical Association. Annual prescriptions plunged from 90 million during each year from 1999 through 2002 to 57 million in 2003.
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