Supporters of hormone replacement therapy (HRT) received discouraging news yesterday when the results from a massive study on estrogen-only treatment after menopause revealed an increased risk of ovarian cancer in patients. The report, which appears in today's issue of the Journal of the American Medical Association, comes just days after a study linked the drug Prempro, a combination of two hormones, estrogen and progestin, to an increased risk of heart attack, stroke, blood clots and invasive breast cancer.

While Prempro is indicated in women with an intact uterus, estrogen alone, sold mainly under the brand name Premarin, is the hormone of choice for women who have undergone hysterectomies. Estrogen, unless balanced by progestin, can cause uterine cancer.

The latest study, conducted by researchers at the National Cancer Institute, followed 44,241 women undergoing estrogen replacement therapy for 20 years. Three hundred and twenty-nine women who used the hormone for 10 years or longer developed ovarian cancer. Researchers concluded that women using estrogen alone were at nearly twice the risk of developing ovarian cancer compared to similar women not taking the hormone. Women who used estrogen alone for 20 years or more were three times as likely to develop ovarian cancer.

In April, a report published in the Journal of the National Cancer Institute revealed similar findings. The study, headed by Dr. Tomas Riman of Falu Hospital in Sweden, examined 655 women aged 50 to 74 diagnosed with ovarian cancer and nearly 4,000 women who did not have the disease. According to the study, women who had used estrogen increased their risk of developing ovarian cancer by 43 percent.