Thermoradiotherapy of refractory malignant tumors: an experience with microwave and RF capacitive hyperthermia

Basic and clinical evidence that hyperthermia with radiation therapy or selected chemotherapy could significantly improve therapeutic ratios has attracted considerable interest. A variety of heating equipment and techniques have been used in many early clinical studies, with encouraging results: 60-70% with complete tumor regression without concomitant increase of normal-tissue toxicity. New generations of hyperthermia systems being developed should improve results significantly. However, since tumor response is directly related to hyperthermic temperature and the uniformity of the temperature distribution within target tissues, adequate characterization of the temperature profile within tumors as well as normal tissues is of primary importance. Clinical experience with microwave hyperthermia treatment combined with radiotherapy has been encouraging (complete regression response rate of 68% in 63 tumors in 50 patients) at Duke and VA Medical Centers, as have the results obtained (complete regression in 21 of 40 tumors treated in one clinic; 13 of 20 tumors treated in another clinic) with an 8-MHz RF capacitive hyperthermia system being evaluated in Japan.