A COMPARISON OF HYPERTHERMIA INHIBITION OF SUBLETHAL RADIATION-DAMAGERECOVERY IN 4 HUMAN CELL-LINES WITH DIFFERENT RADIOSENSITIVITY

Four human cell lines, one normal fibroblast and three tumour lines of differing radiosensitivities were evaluated for recovery from radiati on damage, and for inhibition of this recovery by hyperthermia. The no rmal fibroblast, the glioma and the resistant ovarian carcinoma had ab out the same radiation resistance and sublethal damage recovery (SLDR) capacity. The sensitive ovarian carcinoma cell line had a much lower SLDR capacity. The potentially lethal damage repair (PLDR) capacity wa s greatest in the fibroblast and least in the resistant ovarian carcin oma. Hyperthermia for 30 min at 43 degrees C resulted in inhibition of SLDR and PLDR in all cell lines. Heating immediately after irradiatio n was most effective. In general, SLDR inhibition was greatest in the cell lines with the highest SLDR capacity while there was no such corr elation with PLDR. Hyperthermia was most effective in the four cell li nes tested when given immediately after the first dose of radiation of the split dose regimen. Thus, for clinical fractionated treatment, it may be most efficacious to give hyperthermia immediately after irradi ation.