Simultaneous radiohyperthermotherapy (SRH) is a combined hyperthermia-radiation therapy in which radiation is given during heating. An in vitro study was performed on NIH3T3 cells using 60Co γ-ray for irradiation and a water bath for heat treatment. The thermal enhancement ratio increased after simultaneous treatment compared to sequential treatment with heating for 90 min at 43°C and irradiation. Simultaneous treatment was more cytotoxic than sequential treatment with heating for 20 min at 45°C and irradiation of 6 Gy. A clinical trial was performed on a 57-year-old female with post-operative recurrence of rectal carcinoma. This is the first reported clinical case treated with true SRH in which external irradiation was administered during mid RE capacitive heating. Twelve SRH treatments were performed on the recurrent lesion at a frequency of twice a week for six weeks using the high energy radiotherapy system (Toshiba LMR-15A) and the 13.56MHz capacitive heating system (Omron HEH-500C). Average temperature at the time of irradiation in mid heating was 41.1°C. The patient received 60 Gy in 30 fractions over six weeks. There was a dramatic reduction in pain after treament. The tumor marker CEA level decreased after treatment. On CT images taken after treatment, the tumor site became a low density area which indicated necrosis. There were no side effects encountered. These results suggest that further clinical study of SRH should be performed to clarify its advantages.
