The aim of this study was to compare the grading and prognostic value of L-[methyl-11 C]-methionine ( 11 C-MET) PET in glioma patients with 18 F-FDG PET and contrast-enhanced MRI. Methods: Patients (n 5 102) with histopathologically confirmed gliomas were followed up for an average of 34.6 6 3.8 mo after PET. The median survival was 18 6 4.7 mo in the high-grade glioma group and 58 6 27 mo in the low-grade glioma group. Patients underwent 18 F-FDG PET, 11 C-MET PET, and MRI in the diagnostic and preoperative stage. The ratio of the mean standardized uptake value in the tumor to mean standardized uptake value in contralateral normal cortex (T/N ratio) was calculated. Kaplan-Meier survival analysis and ANOVA were performed. Results: T/N ratios for 11 C-MET PET and 18 F-FDG PET were significantly higher in high-grade gliomas than in low-grade gliomas (2.15 6 0.77 vs. 1.56 6 0.74, P , 0.001, and 0.85 6 0.61 vs. 0.63 6 0.37, P , 0.01, respectively). Median survival was 19 6 5.4 mo in patients with a T/N ratio greater than 1.51 for 11 C-MET PET and 58 6 26.7 mo in those with a T/N ratio less than 1.51 (P 5 0.03). Among the LGGs, median survival was lower in patients with a mean T/N ratio greater than 1.51 for 11 C-MET PET (16 6 10 mo; 95% confidence interval, 1-36 mo) than in those with a T/N ratio less than 1.51 (P 5 0.04). No significant difference in survival in LGGs was based on 18 F-FDG uptake and MRI contrast enhancement. Conclusion: 11 C-MET PET can predict prognosis in gliomas and is better than 18 F-FDG PET and MRI in predicting survival in LGGs.

Our observations confirm the utility of FDG PET as a prognostic tool for the histological grading and survival in patients with gliomas and appears to more than complement pathological grading.

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