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October 1, 2003 — Continuous combined estrogen plus progestin therapy may increase the risk of ovarian cancer and may also increase the number of endometrial biopsies used to diagnose cancers, according to a study based on a new analysis of data from the Women's Health Initiative and published in the October 1 issue of The Journal of the American Medical Association.
"For years, there has been concern about possible associations of gynecologic malignancies with postmenopausal hormone therapy," the authors provide as background information. "The Women's Health Initiative (WHI) trial of estrogen plus progestin provides the first opportunity to examine possible associations of gynecologic malignancies with continuous combined postmenopausal hormone therapy in a large, randomized, double-blind, placebo-controlled setting." The trial was stopped early because health risks (e.g., increased risk of breast cancer) were found to outweigh the benefits of the therapy, and the main study results were published in July, 2002.
Garnet L. Anderson, Ph.D., from the Fred Hutchinson Cancer Research Center, Seattle, and colleagues performed this study to determine the possible associations of estrogen plus progestin on gynecologic cancers and related diagnostic procedures.
The WHI trial involved 16,608 postmenopausal women at 40 U.S. clinical centers who had not had a hysterectomy. The women were randomized in two groups — one that received a placebo and the other a single tablet of 0.625 mg/d (milligrams per day) of conjugated equine estrogens plus 2.5 mg/d of medroxyprogesterone acetate (Prempro). Women who had a prior hysterectomy were randomized to a parallel trial of estrogen alone and that trial is continuing until 2005.
In 5.6 years of follow-up, estrogen plus progestin reduced endometrial cancer rates by 19 percent, but increased ovarian cancer rates by 58 percent. These differences were not statistically significant, however. No evidence of a difference was found between treatment groups in the distribution of tumor anatomy, grade or stage of disease at diagnosis. The numbers of other gynecologic cancers were too small to make reliable conclusions.
There were 27 ovarian cancers diagnosed per 100,000 women per year in women randomized to placebo. With estrogen plus progestin use, this rate was increased to 42 cancers in 100,000 women per year. Thus even if the observed effect is real, ovarian cancer remains a rare disease in women taking these hormones, the authors state.
The authors concluded that, "The possibility of an increased risk of ovarian cancer incidence and mortality remains worrisome, however, and needs confirmation. The increased need for diagnostic procedures in response to bleeding is an added burden and could reasonably affect a woman's decision to use these medicines. These data provide further support for the recently revised guidelines for the use of continuous combined estrogen plus progestin therapy."
Editor's Note: The WHI program is funded by the National Heart, Lung, and Blood Institute, U.S. Department of Health and Human Services. Wyeth-Ayerst Research provided the study medication (active and placebo). Please see the study for the authors' financial disclosures.