When a Florida woman was stricken with a rare brain cancer seven years ago, doctors at the University of Miami School of Medicine treated her with intense bursts of microwaves.

The microwaves heated the cancer cells in a way that allowed drugs injected in the brain to work more effectively on the tumor. The combination of drugs and microwaves turned out to be the only treatment that worked on this form of cancer, which doctors call a "glioblastoma multiforma."

Dr. Don R. Justesen of the Veterans Administration Medical Center in Kansas City told the 146th annual meeting of the American Association for the Advancement of Science today that "seven years later, that lady is alive, even though she was diagnosed with one of the most horrible cancer killers we know about."

Describing microwaves as a "two-edged sword," doctors said that diagnosis and treatment of disease with microwaves is growing throughout the United States. Among the diseases being treated are several kinds of cancer, and those being diagnosed include multiple sclerosis and breast cancer. c

"It is clear that we are developing important tools of a type far safer than any X-ray scanners now in use," said Dr. W. Ross Adey of the Veterans Administration Medical Center in Loma Linda, Calif. "The microwave imaging system now in use at Walter Reed (Institute of Research) is giving us beautiful detail of the brain beyond anything that can be contemplated with X-rays."

Adey said he is using microwaves to peer into the brain to study how cells communicate. Adey told the meeting here that microwaves offer more promise than any other tool in medicine to study the more than 50 billion nerve cells that make up the brain.

A panel of nine doctors using microwaves in diagnosis and treatment defended them, saying that the hue and cry over the ways microwaves can damage cell tissue have created a false image for microwaves.They said microwaves do not damage cells the way that X-rays and radioactivity do because microwaves are not strong enough to break apart the atoms and molecules in a cell.

The panel described the use by doctors in Boston of a new device that scans the body's own microwave emissions, which are so weak they cannot be detected by conventional microwave antennas.

"This device is now being used in a highly successful way to detect early breast cancer," Justesen said. "It is a completely noninvasive technique that apparently is just as successful as X-rays and mammographic techniques being used in most hospitals to screen for breast cancer."

Justesen said the VA medical center in Kansas City uses microwaves to diagnose multiple schloerosis. He said suspected victims of the disease are given weak pulses of microwaves to raise their body temperature, which triggers the failure of some nervous functions in incipient victims of the disease.

"You see it many months ahead of where you see explicit signs of the disease," Justesen said. "It's possible with such early diagnosis to begin treatment far in advance of what we've been able to do in the past."

Despite microwaves' growing use in medicine, the panel of doctors warned that unnecessary exposure if harmful. Research done by Adey shows that microwaves work on the brain, the white cells in the blood, and bone tissue by binding to the negatively charged calcium ions on the surface of cell membranes.