Effect of radiotherapy on brain glucose metabolism in patients operated onfor low grade astrocytoma

Objective-To assess the effect of postoperative radiotherapy on brain gluco se metabolism (CMRGlu) of operated patients with low grade astrocytomas. Methods-PET and F-18-fluorodeoxyglucose was used to measure absolute CMR-Gl u in patients with fibrillary astrocytoma (WHO II) of the frontal lobe, who did (n=7) or did not (n=12) receive radiotherapy subsequent to first debul king tumour resection. In addition, statistical parametric mapping (SPM95) was applied to assess the pattern of relative CMRGlu associated with the fr ontal tumour. Data were compared with 12 healthy controls. Results-A global reduction of absolute CMRGlu was found when either patient s with or without radiotherapy were compared with controls (ROI analysis). Brain areas of relative CMRGlu reduction were found in the brain ipsilatera l and contralateral to the tumour, comparing both patient groups with contr ols by SPM ("tumour diaschisis effect"). Superimposed, absolute CMRGlu in t he contralateral frontal, parietal, occipital cortex as well as in the whit e matter was on average 17% lower in patients receiving radiotherapy than i n patients who did not. Conclusions-The data discriminate a tumour effect from a radiotherapy effec t, and support the view of adverse effects of radiotherapy on brain not dir ectly involved by tumour.