18F-FDG PET in the Assessment of Tumor Grade and Prediction of Tumor Recurrence in Intracranial Meningioma

Purpose: The purpose of this study was to investigate the role of (18)F-fluorodeoxyglucose (FDG) PET in detecting high-grade meningioma and predicting the recurrence in patients with meningioma after surgical resection.

Methods: Fifty-nine patients (27 men and 32 women) with intracranial meningioma who underwent preoperative FDG PET and subsequent surgical resection were enrolled. All patients underwent clinical follow-up for tumor recurrence with a mean duration of 34+/-20 months. The tumor to gray matter ratio (TGR) of FDG uptake was calculated and a receiver-operating characteristic (ROC) curve of the TGR was drawn to determine the cutoff value of the TGR for detection of high-grade meningioma. Further, univariate analysis with the log-rank test was performed to assess the predictive factors of meningioma recurrence.

Results: The TGR in high-grade meningioma (WHO grade II and III) was significantly higher than that in low-grade ones (WHO grade I) (p=0.002) and significantly correlated with the MIB-1 labeling index (r=0.338, p=0.009) and mitotic count of the tumor (r=0.284, p=0.03). The ROC analysis revealed that the TGR of 1.0 was the best cutoff value for detecting high-grade meningioma with a sensitivity of 43%, specificity of 95%, and accuracy of 81%. Of 59 patients, 5 (9%) had a recurrent event. In the log-rank test, the TGR, MIB-1 labeling index, presence of brain invasion, and WHO grade were significantly associated with tumor recurrence. The cumulative recurrence-free survival rate of patients with a TGR of 1.0 or less was significantly higher than that of patients with a TGR of more than 1.0 (p=0.0003)

Conclusion: FDG uptake in meningioma was the significant predictive factor of tumor recurrence and significantly correlated with the proliferative potential of the tumor.