Estrogen Linked to Lower Risk of Breast Cancer and Heart Attack
A new government-funded study has positive news for women who take estrogen to relieve hot flashes and other post-menopausal symptoms. The study, which appeared yesterday in the Journal of the American Medical Association (JAMA), reports and that certain women have a much lower risk of breast cancer and heart attack years after estrogen-only therapy. However, taking the two hormones estrogen and progestin has been linked to an increased risk of breast cancer and researchers emphasize that women and their doctors need to remain aware of this.
The study was part of the National Institute of Health‘s Women’s Health Initiative, a 15-year research program. It looked at 10,739 women who had had a hysterectomy, the surgical removal of the uterus. In the US, one-third of women in their 50s have had a hysterectomy. Says the New York Times Well blog:
While most women in the hormone study were taking combination hormone therapy, women without a uterus took estrogen alone or a placebo for about six years and were followed for nearly 11 years. The estrogen-only group was not given progestin, which is prescribed only to protect the uterus from the harmful effects of estrogen. Although all the women in the estrogen study stopped using the treatment in 2004, the investigators have continued to monitor their health, as is typical in large clinical trials.
The most surprising new finding relates to breast cancer. The women with hysterectomies who used estrogen alone had a 23 percent lower risk for breast cancer compared with those who had taken a placebo. This is in stark contrast to the higher risk of breast cancer shown in the estrogen-progestin part of the trial.
Again, the study’s authors emphasized that the results do not change recommendations for women who are taking the combination hormone therapy.
But new findings are reassuring news for women who only take estrogen for relief from post-menopausal symptoms, though an accompaning editorial to the study raised a number of caveats, noting that
…the design of the initiative, which is skewed toward older women and stopped all forms of hormone treatment after several years of use, does not match the way doctors typically prescribe treatment to women in their 50s at the onset of menopause.
In addition, the type of estrogen used in the study — conjugated equine estrogens, estrogen compounds derived from the urine of pregnant mares and marketed by Wyeth Pharmaceuticals under the brand Premarin — is a brand that is not being used as much by women. More women have been choosing to use estradiol, which is chemically similar to a woman’s natural estrogen.
The JAMA study’s researchers themselves point out that the benefits of estrogen differ depending on a women’s age, health and type of hormone used, with the data looking more favorable for younger women:
The data indicate that for every 10,000 women in their 50s, those using estrogen would experience 12 fewer heart attacks, 13 fewer deaths and 18 fewer adverse events like blood clots or stroke in a given year, compared with those taking a placebo.
But the risks of estrogen use were pronounced in older women. For every 10,000 women in their 70s, using estrogen would cause 16 extra heart attacks, 19 extra deaths and 48 serious adverse events.
Still, researchers also note that their new study offers further evidence that hormone treatment may have health benefits and that hormones are not simply good or bad; that, for some women, hormones may be, as Dr. Rowan Chlebowski, an author of the study and a medical oncologist at Los Angeles Biomedical Research Institute, says “a good choice.”