Estrogen Therapy May Not Be Cancer Threat

Postmenopausal women treated with estrogen therapy for seven years did not experience an increased risk of breast cancer, a U.S. study found.

The Women’s Health Initiative Estrogen-Alone trial, which randomized women with prior hysterectomy to conjugated equine estrogens or placebo, was stopped earlier because of increased stroke incidence and no reduction in risk of coronary heart disease.

Marcia L. Stefanick, of Stanford University and colleagues with the WHI study, analyzed the data from the conjugated equine estrogens alone group of the WHI study to determine the effects of conjugated equine estrogens on breast cancers and mammographic findings.

The study, published in the Journal of the American Medical Association, found conjugated equine estrogens alone for seven years does not increase breast-cancer incidence in postmenopausal women with hysterectomy and may decrease the risk of early-stage disease and ductal carcinomas.

The result is in clear contrast to the WHI trial of conjugated equine estrogens combined with medroxyprogesterone acetate in women with a uterus, which showed a significant increase in breast-cancer incidence over a mean of 5.6 years of follow-up.