EFFECT OF HEATING ORDER ON RADIATION RESPONSE OF MOUSE TUMOR AND SKIN

The response of C3H mouse mammary adenocarcinomas and skin to irradiation either immediately before, or during heating at 43°C was evaluated. The therapeutic gain factor (TGF) was 1.3 for irradiation during heating, but only 0.9 for irradiation prior to heating. X-irradiation also was done 2 hr before, during or 2 hr after heating at 42.5°C. Heating times were 15, 30 and 60 min. There was no TGF for irradiation following 60 min. heating. When irradiation preceded 1 hr of heating, the TGF was 1.2. Therapeutic gains also were achieved for 30 min. of heating regardless of sequence, although the largest TGF of 1.3 was obtained for simultaneous treatment. TGFs of 1.3 were obtained for 15 min. heating 2 hr prior to or during irradiation. The greater TGFs for shorter heating times resulted from the small effect of heat on skin response, but significant effect on tumor control. © 1979.