[Radiochemotherapy-related changes in the brain parenchyma of glioma patients evaluated repeatedly by C15O2, C15O, 15O2, and 18F-fluorodeoxyglucose (FDG) PET].

The aim of this study was to evaluate effects of radiochemotherapy on blood flow and metabolism using C15O2, C15O, 15O2, and 18F-fluorodeoxyglucose positron emission tomography (PET). Conventional, external radiotherapy (180-200 cGy/5 fractions/week) using 60Co or a 10 MV linear accelerator was given in conjunction with chemotherapy of nimustine hydrochloride (ACNU) and tegafur (FT-207) in eight patients with gliomas. Regional cerebral blood flow (rCBF), blood volume (rCBV), oxygen extraction fraction (rOEF), oxygen consumption (rCMRO2), and glucose consumption (rCMRG1) were longitudinally examined before the treatment, and at an early stage (within one month) and a late stage (three to thirty-one months with a mean of 12 months) after radiochemotherapy. Contralateral gray and white matter to the tumor was selected as regions of interest (ROIs), because these portions were irradiated with larger doses compared to other brain parenchymal regions through parallel opposing fields. Maximum doses to the ROIs varied between 20 and 61 Gy. Calculated as a function of time-dose-fractionation, nominal standard doses (NSD) ranged from 566 to 1729 ret, and 344 to 1062 neuret; equivalent doses (ED) equaled 432 to 1327 rads. At the early stage, rCBF and rCBV increased in the contralateral gray and white matter; gray matter rOEF decreased significantly (p less than 0.05 by a paired-t test) from that of the pretreatment study, probably due to decompression of the tumor bulk and radiochemotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)