Single dose X-irradiation and concomitant hyperthermia on a murine fibrosarcoma

The objectives of this study were to quantitate the effects of local tumor hyperthermia (LTH) and concomitant x-irradiation (RAD) on a moderately radioresistant murine fibrosarcoma in situ. Comparisons were made to the combined treatment response on the Ridgway osteogenic sarcoma, a radio sensitive tumor previously used in this laboratory and to establish the Meth-A fibrosarcoma as a model system for combined modality studies. 1.0 cm3 tumors were exposed to single doses of RAD ranging from 0.5-3.5 krad alone or 0.5-2.3 krad in combination with LTH (water bath at 43.1 +/- .05 C for 20 minutes) applied immediately postirradiation. LTH significantly enhanced the action of radiation as measured by tumor volume analysis, mean survival time and cures. The ratio of radiation doses vs. RAD + LTH required to produce an equivalent response ranged from 1.4 to 2.5 depending upon the endpoints evaluated. These findings are consistent with single dose studies on the radiosensitive Ridgway osteogenic sarcoma and suggest that the tumoricidal effectiveness of combination radiation and hyperthermia cannot be predicted on the basis of the radiation alone responsiveness of tumor.