A controversial abortion pill developed in France may halt the growth of some types of breast cancer tumors, but researchers say it isn't being actively tested in the United States because of government policy.

Studies have shown that RU-486, which acts to block the action of some hormones, may have important uses in treating breast cancer and other diseases affected by those hormones, Dr. Gary D. Hodgen of the Eastern Virginia Medical School said Saturday.Hodgen, part of a panel presenting new studies on RU-486 at the American Association for the Advancement of Science, said the drug and others of similar chemistry have been shown in studies to slow or stop the growth of some types of breast tumors.

The drug and others like it, he said, also have been shown in studies to aid in cervical dilation, an effect that eases births in difficult deliveries.

Other studies, he said, have shown that RU-486 may be valuable in treating endometriosis, a painful condition in which tissue lining the uterus starts growing elsewhere in the pelvis. Serious cases now require surgery. About 15 percent of all women have at least one episode of this disease and it commonly leads to hysterectomies.

The researcher said that RU-486 is being prescribed in France for the treatment of Cushing's Syndrome, a serious endocrine disorder that can cause high blood pressure, weight gain and emotional disturbances.