Focused microwave phased array thermotherapy for primary breast cancer

Background: A pilot safety study of focused microwave phased array thermotherapy in the treatment of primary breast carcinomas was conducted. Methods: Ten patients with breast carcinomas beneath the skin surface that ranged in maximal clinical size from 1 to 8 cm (mean, 4.3 cm) were treated with the breast compressed in the prone position. We planned to deliver a tumor thermal dose equivalent to 60 minutes at 43degreesC. Breast imaging and pathology data were used to assess efficacy. Results: For the 10 patients, the mean tumor equivalent thermal dose was 51.7 minutes, the mean peak tumor temperature was 44.9degreesC, and the mean treatment time was 34.7 minutes. Ultrasound imaging demonstrated a significant reduction in tumor size (mean, 41%) 5 to 18 days after thermotherapy in 6 (60%) of 10 patients. A significant tumor response on the basis of reduction in tumor size or significant tumor cell kill occurred in 8 (80%) of 10 patients. Conclusions: With sufficient skin cooling, delivery of focused microwave phased array thermotherapy is safe in treating breast carcinomas when used alone, and some potential efficacy was demonstrated at the tumor thermal doses administered. Increased tumor thermal dose efficacy studies in larger patient populations for improved breast conservation should be investigated.