The efficacy of combining radiation and hyperthermia therapies

Twelve patients with malignant tumors who were unlikely to benefit from radiotherapy alone, were given radiation therapy in combination with hyperthermia. The heating apparatus used in the study was HEH 500C of RF (radio frequency) capacitive type. All patients received a treatment with radiation of 400rad by 60Co twice weekly followed by hyperthermia. A minimum of 42deg C of heat for 30 to 40 minutes was performed. Only six patients underwent the combination therapy five times or more. Of these six cases, the % regression of tumor was determined by means of palpation or CT scan, and the therapeutic effect was classified into four grades. The results were one case of CR (100% regression), one case of PRa (80∼99%), one case of PRb (50∼79%) and three cases of NR (less than 50%). Two out of three PRb or better cases were related to superficial tumor and no correlation was observed between tumor histology and therapeutic effect. For objective assesment of the efficacy of hyperthermia, the thermal dose of each of the six cases was determined according to the concept of Equivalent time at 43deg C. PRb or better cases correlated with large thermal doses, thus it was considered that positive effects result from heating at 42.5deg C or higher for over 30 minutes. As for deeply located tumors, only one out of eight cases was classified PRb or beter. The use of hyperthermia against a tumor of this type will require solving several problems, including improvement in the heating apparatus, and a reduction of side effects. (author)