Since 1976, two groups of patients have been treated with local microwave hyperthermia immediately following ionizing radiation. Group A patients had measurable multiple lesions assigned radiotherapy only, microwave hyperthermia only, or combined treatment. Ionizing radiation in 200-600 rad fractions was used 2-5 times per week to a total of 1800-4200 rad in 5-14 fractions. Group B patients had combination treatment only, with radiation fractions of 200-600 rad 2-5 times per week to a total of 2000-4800 rad total in 6-20 fractions. Both groups received hyperthermia (42-44 C) 2-3 times per week, maximum ten sessions in four weeks. The 19 patients treated have had squamous cell carcinoma, adenocarcinoma, malignant melanoma, plasmacytoma, epithelioid sarcoma, and undifferentiated carcinoma. After more than 150 hyperthermia sessions, we find: (1) local hyperthermia with microwave alone or in combination with ionizing radiation can be used with excellent normal tissue tolerance provided local tissue temperatures are carefully monitored and controlled; (2) a higher level of heat induction in tumor tissue as compared to surrounding normal tissues; (3) repeated hyperthermia at 42-43.5 C for 45 minutes per session immediately following photon irradiation yields a favorable therapeutic result, occasionally dramatic. Local microwave hyperthermia in combination with radiotherapy offers the possibility of substantial impact on clinical cancer therapy, whether of curative or palliative intent.

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