THERMOTOLERANCE EFFECTS ON THERMORADIOSENSITIZATION IN HUMAN GLIOMA-CELLS

Human glioma cells were tested to evaluate thermotolerance (TT) develo pment and its effect on radiosensitization. The data show that long du ration mild hyperthermia (LDMH) at 40, 41 and 42 degrees C when given before acute irradiation resulted in increased radiosensitization with heating time. Furthermore, radiosensitization was not reduced by TT. When LDMH was given before 45 degrees C hyperthermia there was evidenc e of TT development which reduced radiosensitization compared to heati ng at 45 degrees C alone. For 40 and 41 degrees C heating the effect w as maximum for the 8h heating time while for 42 degrees C it was gener ally maximum for the 4h heating time. At longer heating times of 24 to 48 h the effect of TT declined. Thus while LDMH itself does not displ ay TT for radiosensitization it can in fact produce a TT effect on rad iosensitization when used in a stepup-heating protocol with 45 degrees C.