A panel of experts convened by the National Institutes of Health to recommend treatment for early breast cancer yesterday enthusiastically endorsed the combination of lumpectomy and radiation as "preferable" to mastectomy, but failed to reach a conclusion on whether patients should receive further treatment with drugs.

"We would like to have been able to come out with a series of. . . easy, crisp, defined recommendations for each patient, according to a defined set of criteria," said panel chairman William C. Wood, an associate professor of surgery at Harvard Medical School.

Instead, he said, "we have a situation in which each woman and her physician has to review what we know about her risk, the benefit she is likely to enjoy from therapy and the toxicity of therapy."

Some physicians found the lack of a recommendation disappointing because the panel's job was to help women and their doctors by sifting through all the available data and coming up with guidance for them.

"Ideally, this conference should have been the focal point to clear up all the questions," said William McGuire, chief of medical oncology at the University of Texas Health Science Center at San Antonio. "I don't think it said enough."

Breast cancer incidence in the United States is rising, with an increasing proportion of cancers being detected at early stages in which the role of chemotherapy and other drugs is highly controversial.

About 80,000 of the 120,000 American women found to have breast cancer each year have early breast cancer, in which the tumor has not spread to nearby lymph nodes.

In about 70 percent of such cases, the cancer is cured by the initial treatment alone -- either mastectomy or lumpectomy combined with radiation. In the remaining 30 percent, the cancer recurs.

In an effort to lower the recurrence rate, patients with early breast cancer have been treated in a variety of studies either with chemotherapy, which attacks the cancer cells directly, or with tamoxifen, a drug that blocks the action of the hormone estrogen, believed to promote tumor growth. At least 10 studies have shown such drugs can cut the recurrence rate from 30 percent to about 20 percent.

But the drugs have potentially serious side effects, and so far studies have not shown that the drugs improve patients' overall survival. Nor can researchers reliably identify which patients will benefit from the drugs and which will be cured by surgery without the need for further treatment.

The panel said the many unanswered questions "make it imperative" doctors offer women the opportunity to participate in studies comparing various treatment alternatives. Only about 3 percent of women with breast cancer who are potential candidates enter such studies.

If a woman does not wish to enroll in a study, the panel said she and her doctor should consider a variety of factors to try to predict the risk that her tumor will recur and to decide whether the cost and side effects of drug treatment are worthwhile.

Such factors include the size of the tumor, the microscopic appearance of the cancer cells, and laboratory tests to measure cell growth rate and detect whether they contain receptors for the hormones estrogen and progesterone.

Wood acknowledged the complexity of weighing such factors, saying it had taken the panel more than 40 hours to assess the available research on the subject. "I anticipate that the average physician and patient would be unable to cover it all," he said.

The panel concluded that all patients with early breast cancer are at some risk for tumor recurrence, but that in those with very small tumors -- one centimeter in diameter (about four-tenths of an inch) or less -- the risk is only about 10 percent. It concluded there is no need to treat such patients with chemotherapy or other drugs, unless they receive the treatment as part of a study.

Regarding choice of surgery, the panel found that lumpectomy combined with radiation therapy offers patients the same chance of survival as a mastectomy, and is "preferable" for most patients with early cancer because it preserves the breast. Although experts have been making similar recommendations for several years, the majority of American women with breast cancer still have mastectomies.