Object: The aim of this study was to evaluate the usefulness of combined use of positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) and (11)C-methionine (MET) for the preoperative evaluation of gliomas and to investigate the feasibility of PET in glioma surgery.
Methods: Preoperative FDG (n=25) and/or MET (n=22) PET studies were performed in 26 patients with primary and recurrent adult gliomas. We qualitatively (visual analysis) and quantitatively evaluated the uptake of both tracers in the tumor location. For quantitative analysis, data were analyzed by a region of interest method using the standard uptake value (SUV) and a calculated uptake ratio. We investigated the correlation among the tracer uptake ratios, histological tumor grading and tumor proliferation activity.
Results: On visual inspection, no patient (0/9) with high uptake of FDG had low grade gliomas and 94% (14/15) had high grade gliomas, while uptake of MET was present in all patients. On quantitative analysis, histological tumor grade was most reflected in FDG uptake ratio compared with contralateral white matter. The tumor/normal brain (T/N) uptake ratio of MET increased stepwise with increasing histological grade but was not significantly different from tumor grade. In comparison of FDG and MET uptake ratio with proliferation activity, a significant correlation was shown for FDG uptake ratio, but not for the T/N ratio of MET.
Conclusions: MET is useful in detecting and delineating the extent of the tumor, but not in evaluating tumor grade and proliferative activity. The FDG uptake ratio correlates well with tumor grade and proliferative activity. Preoperative PET studies with FDG and MET play complementary roles in the planning of glioma surgery, and integrated information from both tracers helps us to plan the extent of tumor resection.