ANTITUMOR EFFECT OF IRRADIATION FOLLOWED BY HYPERGLYCEMIA AND HYPERTHERMIA - THE DEPENDENCE ON TUMOR SIZE AND BLOOD-FLOW

The interrelationship of three tumour parameters-volume, blood flow an d growth delay-was evaluated after irradiation alone or combined with hyperglycemia (HG) and hyperthermia (HT). The experiments were perform ed on Ehrlich carcinoma tumours 5, 7 or 9 days after intramuscular imp lantation when they reached a mean volume of approximately 0.17, 0.46 or 0.90cm(3) respectively. Tumours were irradiated at a dose of 12.5 G y. In groups of trimodality therapy, induction of HG (5 i.p. injection s of glucose during a 2-h period, total dose of glucose 10.4 g/kg) was started immediately after irradiation, and HT (water bath, 43 degrees C, 30 min) was given 3 h later. Regardless of the method of therapy, blood flow in the central part of each tumour was measured 4 and 7 h a fter irradiation by Xe-133 clearance technique. It was shown that if t umours were treated by irradiation alone, both tumour blood flow and g rowth delay declined with increasing tumour volume. There was no corre lation between individual values of tumour blood flow intensity and gr owth delay within each size group, and only all the data pooled togeth er showed a significant direct relationship between these two paramete rs. In contrast, for radiotherapy with HC and HT, the antitumour effec t increased with tumour volume. Blood how was strongly inhibited by ra dio-modifiers; the larger tumours, the lower levels of perfusion were observed. There was a pronounced trend of increased tumour growth dela y with decreased blood flow for tumours of the same volume, and these parameters were highly correlated if all individual data were analysed together regardless of tumour size. It was concluded that postirradia tion blood how inhibition plays a significant role in the tumouricidal effect of irradiation with HG and HT. The monitoring of tumour perfus ion may be useful for the prediction of the effectiveness of such post irradiation modification, which is especially attractive in radiothera py of large advanced tumours.