Correlation of ¹¹C-methionine uptake with tumor grade in patients with newly diagnosed meningioma in comparison with ¹⁸F-FDG uptake

Objectives: Patients with World Health Organization (WHO) grade II-III meningioma compared with grade I meningioma exhibit an aggressive behavior. The purpose of this study was to compare capability of ¹¹C-methionine (MET) PET and 2-deoxy-2-¹⁸F-fluoro-D-glucose (FDG) PET for grading meningioma.

Methods: Seventeen patients with intracranial meningioma who underwent preoperative both MET and FDG PET studies and subsequent surgical resection were enrolled. Grading of the tumor was performed according to the WHO classification. PET results were evaluated by visual and semi-quantitative analysis. For semi-quantitative analysis, the maximal standardized uptake value (SUV) for tumor (T) and the mean SUV for contralateral normal brain tissue (N) were calculated and T/N ratio was determined.

Results: Seven patients had WHO grade I and 10 had WHO grade II meningioma. The FDG PET study revealed hypometabolism in 7 meningiomas (4 grade I and 3 grade II), isometabolism in 4 meningiomas (3 grade I and 1 grade II), and hypermetabolism in 6 meningiomas (all grade II). High uptake of MET was observed in all 17 meningiomas, in contrast to the low uptake in surrounding normal brain tissue, allowing a clearer demarcation of the tumor boundary than that provided by FDG. The T/N ratio of MET was significantly higher than that of FDG (p<0.001). Using MET PET, T/N ratio in grade II meningioma was significantly higher than that in grade I meningioma (p<0.05). There was no significant difference between grades I and II meningioma for FDG T/N ratio.

Conclusion: The results of this preliminary study suggest that, compared with FDG, MET may better image meningioma because of low uptake in surrounding normal brain tissue. MET may be useful for evaluating the tumor grade in patients with meningioma. Research Support: