[Therapeutic gain factor of hyperthermia].

We studied the radiosensitizing effects and therapeutic gain factor (TGF) of hyperthermia, in vivo, using the squamous cell carcinoma of the mouse. Radiation exposures of 2,000 rads X-ray were combined with 42 degrees C, 43 degrees C and 44 degrees C heating, simultaneously or separately 1, 2, 4 and 6 hours before or after the radiation exposures. Radiation effects were measured with regrowth delay of the tumor and the Denekamp scoring system was used for the skin reaction. The results showed that the radiosensitizing effect of hyperthermia is strongest when heat is applied simultaneously with radiation. But in that case we cannot get a TGF over 1, which means no therapeutic advantages are 42 degrees C of heat applied 6 hours after radiation exposure or 43 degrees C of heat applied 4-hours after the exposure.