Clinical characteristics of meningiomas assessed by 11C-methionine and 18F-fluorodeoxyglucose positron-emission tomography

The clinical course of meningioma varies from case to case, despite similar characteristics on magnetic resonance (MR) imaging. Functional imaging including C-11-methionine and F-18-fluorodeoxyglucose (FDG) positron-emission tomography (PET) has been widely studied for noninvasive preoperative evaluation of brain tumors. However, few reports have examined correlations between meningiomas and findings on C-11-methionine and FDG PET. The objective of this study was to clarify the relationship between tumor characteristics and C-11-methionine and FDG uptake in meningiomas. For 68 meningiomas in 51 cases, C-11-methionine uptake was evaluated by measuring both mean and maximum tumor/normal (T/N) ratio for the whole area of the tumors. FDG uptake in 44 of those meningiomas was also analyzed. Tumor size was measured volumetrically, and tumor-doubling time was estimated. Histopathological evaluation was performed in 19 surgical cases. Mean and maximum T/N ratios of C-11-methionine PET were significantly higher in skull-base lesions than in non-skull-base lesions. Correlations of mean and maximum T/N ratio of C-11-methionine PET with tumor-doubling time, MIB-1 labeling index, microvessel density and World Health Organization grading were not significant. Mean T/N ratio of C-11-methionine PET correlated significantly with tumor volume according to logarithm regression modeling (P < 0.0001, R = 0.544). However, mean and maximum T/N ratio of FDG-PET correlated with none of the tumor characteristics described above. These results suggest that C-11-methionine uptake correlates with tumor volume, but not with tumor aggressiveness.