A National Cancer Institute committee is believed likely to recommend today that surgeons all but abandon the radical form of breast surgery still being done on about 25,000 women a year, or one woman in six with early breast cancer.

New findings to be presented to the expert panel at a conference at the National Institutes of Health will show that simpler breast removals have saved as many lives as the more radical operations in more than 1,600 women followed for nearly six years at 34 medical centers. After hearing the findings, a majority of the committee is expected to endorse the simpler operation.

The new statistics show that what surgeons call a "simple" mastectomy, removal of the breast, is as effective in treating early breast cancer as the "radical" operation, which removes not only the breast but also the chest wall muscles, causing more disabliity and disfigurement.

One woman in 13 gets breast cancer, and there are 160,000 new cases a year.

Many surgeons have already simplified their operating methods as they followed the research results over the past few years. But others have been waiting for at least five years' follow-up of treated women and some review by an expert group like that assembled at the National Institutes of Health in Bethesda today.

There will be some disagreement with the conclusion that simpler surgery is equally effective in most cases. The most prominent dissenter is expected to be Dr. Jerome Urban of Memorial Sloan Kettering Cancer Center, New York, who thinks that 10 years or more of followup are necessary before reaching any conclusions.

But most surgeons, Dr. Joseph Allegra of the cancer institute said yesterday, now feel that "the radical mastectomy is no longer the preferred operation" in primary, localized breast cancer, or even in breast cancer that has spread to the underarm tymph nodes.

Most surgeons, he reported, feel they can just as effectively do a simpler operation-either the "simple" mastectomy or a "modified radical," meaning removal of the breast and at least some underarm lymph nodes-often with added treatment when there is disease in the lymph nodes.

The figures that back this up will be reported by Dr. Bernard Fisher of the University of Pittsburgh, coordinator of the nationwide study financed by the cancer institute.

Fisher has said most recently that among women with no lymph node disease-that is, where the cancer is truly localized in the breast-76 percent survived for five years after a radical mastectomy, 74 percent after removal of the breast alone plus followup radiation and 73 percent after breast removal alone.

He reported that when there was spread of the cancer to the nodes, 59 percent of the women survived for five years after the radical operation, and 57 percent survived after a simple mastectomy plus radiation.

"In short," Fisher said in an interview Sunday, the fast that all these figures are so close shows "there were no real differences."

Today he will report his statistics after another 10 months' observation, with "no changes of more than a few percentage points," that is, "no real changes."

What all this means in treatment, Allegra said, must be considered in the light of other advances. The main one is increasing use of anticancer chemicals where there is advanced disease, as revealed by lymph node involvement.

"For this reason," Allegra said, "I'd say that the preferred operation in early cancer today is the modified radical-the removal of the breast and some lymph node tissue," then further treatment if cancer is found in the nodes.

Some surgeons have moved to an even simpler operation for some patients with small, early cancers-a "lympectomy" or "segmental" operation that removes only a quarter of the breast and leaves the rest.

"There's a lot of information to suggest that in certain patients this will be of real value," Fisher said. But he added, "we still don't have the data," to be certain, or to know which patients can benefit safely.

Meanwhile the most recent national figures, gathered in 1977, show that the form of radical surgery that Fisher now considers superfluous was still being done in 21 percent of all breast cancer operations.