A panel of outside experts urged the Food and Drug Administration yesterday to alert physicians and women to preliminary data relating use of a hormone called DES to breast cancer.

Women who were prescribed the estrogen in efforts to avert miscarriages "should be encouraged to obtain breast examinations," the Advisory Committee on Obstretrics and Gynecology decided in the first session of a two-day meeting at agency headquarters in Rockville.

The initial report "does provide evidence for concern" despite its "preliminary nature and its limitations," nine members of the panel said in a unanimous statement. They also agreed unanimously that the results do not prove a cause-effect relationship.

The panel decided that existing information on the potential of other estrogens to cause breast cancer in women is "so limited that an answer at this time cannot be provided."

At least 2 million American women are believed to have taken DES (diethylstilbestrol to prevent miscarrages during the quarter century ended in late 1971.

Earlier that year, scientists reported that daughters born to possible one in 1,000 of the women develop sometimes fatal vaginal cancer. In 1975, other studies discovered that a larger proportion of sons of DES mothers developed effects of the reproductive tract.

The evidence of breast cancer in some users was discovered during a government-financed follow-up of an experiment at the University of Chicago in 1951-52 that demonstrated the ineffectiveness of DES in preventing miscarriages.

Data in the follow-up were analyzed by Dr. Sidney M. Wolfe, director of the Health Research Group which is financed by Ralph Nader's Public Citizen Inc.

For the past six years, the FDA has urged physicians not to prescribe DES and related estrogens to prevent spontaneous abortions. But Wolfe protested that the agency "continues to put its stamp of approval on prescribing this dangerous drug for trivial and/or questionably effective purposes such as relieving breast engorgement or suppressing lactation after delivery."

For treatment of these two conditions in the year ended June 30, doctors wrote 121,000 prescriptions for DES and 165,000 for other estrogens.

Yet, he said, one of the manufacturers of DES, Eli Lilly & Co., cautions doctors that women respond well to other therapy and pain killers.

Wolfe also cited data showing doctors wrote 12,000 estrogen prescriptions for acne, although the FDA does not approve this, and an "absolutely outrageous" 133,000 additional estrogen prescriptions for treatment of mental disorders - although "no evidence" shows the drugs to be effective over a fairly long term.

He said the FDA should withdraw approval for the use of DES and other estrogens in all medical conditions that are "trivial in comparison to the dangers of these drugs."

In a related action yesterday, the panel board heard the first public report on a study in Atlanta showing a pregnancy rate of 6.7 per cent in rape victims who received prescriptions for DES pills at Grady Memorial Hospital for use as "morning after contraceptions."

Panel members emphasized that the study did not determine whether the prescriptions were filled or the pills actually taken. They also cited other evidence - some of it unpublished - showing DES may be completely effective as a postcoital contraceptive if properly used.

The committee said DES should "not be used as a standard approach" to postcoital contraception. "Rather, its use should be individualized."