CLINICAL HYPERTHERMIA WITH A NEW DEVICE - THE CURRENT SHEET APPLICATOR

Purpose: The current sheet applicator (CSA) is a newly developed micro wave hyperthermia device. Advantages over commercial microwave applica tors include its small size and high ratio of heating area to physical aperture area. These physical characteristics make the CSA excellent for heating constricted areas and allow the use of arrays of CSAs over large surfaces. This study examines the clinical efficacy of the CSA for heating superficial malignant tumors. Methods and Materials: From December 1989 through October 1991, 19 patients with recurrent or meta static superficial malignant tumors were treated once or twice weekly to 30 hyperthermia fields using one to four CSAs. Each field received from one to four hyperthermia treatments for a total of 74 treatments. The treatment objective was to elevate the tumor temperature to a min imum of 42.5 degrees C for 30 min (2 patients) or 60 min (17 patients) . Intratumor temperatures were measured with percutaneous fiberoptic t hermometry probes. All patients received concurrent fractionated radia tion therapy with total dose ranging from 20 to 65 Gy (median 46 Gy). Seventeen of the 30 fields had been previously irradiated to a median dose of 50 Gy. Results: Mean values for the maximum temperature, avera ge temperature, and minimum temperature were 43.6 degrees C +/- 1.0, 4 2.2 degrees C +/- 1.4, and 41.0 degrees C +/- 1.5, respectively. Mean values for T-50 and T-90 were 42.2 degrees C +/- 1.1 and 41.0 degrees C +/- 1.3, respectively. The overall response rate for all assessable fields was 96%. Only three responding tumors have progressed with a me dian follow-up period of 6 months. Treatment related morbidity was gen erally mild and self-limited. Conclusion: The CSA is a promising new m icrowave hyperthermia device capable of heating superficial tumors to therapeutic temperatures. When used in combination with radiotherapy, response rates are excellent without excessive toxicity.