THE RESPONSE OF HUMAN TUMOR BLOOD-FLOW TO A FRACTIONATED COURSE OF THERMORADIOTHERAPY

The response of human tumour blood flow to a fractionated course of th ermoradiotherapy was documented in four superficial but bulky tumours (three adenocarcinomas, one melanoma). Blood flow was measured 15, 30, 45, and 60 min after the onset of heating. These measurements were ma de at the same intratumour point during each heat fraction by use of a modified thermal clearance technique in which a correction was made f or the heat dissipated by thermal conduction. This point was at least 2 cm beneath the surface in the central portion of the-tumour. Extrace llular pH was measured within 1 cm of this point prior to the first he at fraction and 2-3 weeks later. Hyperthermia was administered for 60 min, twice a week for 4 weeks by use of a 16-channel 915 MHz microwave applicator. Each patient also received a radiation dose of 40 Gy frac tionated at 2Gy/fx, five times a week (adenocarcinomas) or 4 Gy/fx, tw ice a week (melanoma). Blood flow remained relatively constant during heating after steady state conditions were attained. However, an overa ll decrease in tumour blood flow was observed in each patient over the course of thermoradiotherapy. In each case, a relatively small decrea se in blood flow occurred between most heat fractions which resulted i n an overall decrease which ranged from 50-100%. However, there was a tendency for blood flow to increase following the initial heat fractio n at points where the steady state temperature was approximately 41 de grees C or less. Extracellular pH increased in two of three patients a nd decreased in the other.