CAMBRIDGE, Mass. -- A breast cancer treatment based on MIT radar research that was originally intended to detect space-borne missiles is showing promise in the final phase of clinical testing.

Preliminary results to be presented on Wednesday, April 21 at the 9th International Congress on Hyperthermic Oncology in St. Louis show that women with early-stage breast cancer who received the MIT treatment prior to lumpectomy had a 43 percent reduction in the incidence rate of cancer cells found close to the surgical margins. This is important because additional breast surgery and/or radiation therapy are often recommended for patients that have cancer cells close to the edge of the lumpectomy surgical margin.

Since October 2002, 90 women with early-stage breast cancer have enrolled in the study, in which microwave energy focused externally on the breast is delivered to tumors prior to lumpectomy. The goal is to use focused heat to kill tumor cells and reduce additional surgery. The current results are based on the 64 women who have completed the study.

Treating cancer with heat is not a new idea, but "researchers were having trouble using it to treat tumors deep within the body," said Alan Fenn, a senior staff member at MIT Lincoln Laboratory and inventor of the technique. Further, it's difficult to deliver the heat only to cancer cells and not overheat normal tissue.

The microwaves in the new technique "heat -- and kill -- cells containing high amounts of water," he said. Cancer cells have a high water content (around 80 percent), while healthy breast tissue contains much less.

The outpatient procedure uses a single tiny needle probe to sense and measure parameters during treatment. Side effects appear to be minimal.

Patients in the thermotherapy group of the current study receive a minimally invasive heat treatment prior to surgery and radiation therapy, while patients in the control group receive surgery alone prior to radiation therapy. Preliminary results indicate that in the thermotherapy group, 5 of 30 (16.7%) patients had tumor cells close to the surgical margins, whereas in the group receiving surgery alone, 10 of 34 (29.4%) patients had tumor cells close to the margin.