GLUCOSE METABOLIC CHANGES IN NONTUMORAL BRAIN-TISSUE OF PATIENTS WITHBRAIN-TUMOR FOLLOWING RADIOTHERAPY - A PRELIMINARY-STUDY

Purpose: Our goal was to measure the effect of radiotherapy on the bra in glucose metabolism of tumoral and nontumoral tissue of patients wit h brain malignancies. Method: Fifteen patients with primary or metasta tic brain tumors were studied with 2-deoxy-2-[F-18]fluoro-D-glucose an d PET prior to radiotherapy, and nine of them were rescanned 1 week af ter completing radiotherapy. Results: Brain metabolism in patients (al l brain regions except for tumoral and edematous tissue) was lower tha n that of matched controls (34.0 +/- 8.3 vs. 46.5 +/- 6.4 mu mol/100 g /min; p less than or equal to 0.0001). Five of the nine patients retes ted after radiotherapy showed decrements in tumor metabolism (47 +/- 1 0%; p less than or equal to 0.05) and increases in brain metabolism (1 0 less than or equal to 4%; p less than or equal to 0.004), and the ot her four showed no changes in tumor or in brain metabolism Radiotherap y-induced changes in tumor metabolism were negatively correlated with changes in brain metabolism (r = 0.85, p less than or equal to 0.004), but not with changes in tumor volume (assessed with MR images). Concl usion: The study indicates that radiotherapy-induced increases in meta bolism of nontumoral tissue are secondary to decreased tumor metabolic activity and not just due to volume reduction.