Fasting improves discrimination of grade 1 and atypical or malignant meningioma in FDG-PET.

UNLABELLED

We investigated the use of PET with 2[18F]fluoro-2-deoxy-D-glucose (FDG) to discriminate between atypical or malignant and grade 1 meningiomas. The influence of fasting state and high-dose corticosteroid medication was analyzed retrospectively.

METHODS

Preoperative PET scans of 75 patients with suspected diagnosis of intracranial meningioma were evaluated using standardized uptake values (SUV) and tumor-to-contralateral gray matter ratios (TGR) of FDG uptake. Fifty-one of 75 patients fasted before the PET scan, and 27 of 75 patients were studied under high-dose corticosteroid medication. Eighteen tumors had recurred. PET results were compared to histopathological grading.

RESULTS

PET correctly identified 8/9 atypical or malignant meningiomas and 58/66 grade 1 meningiomas using TGR and a threshold of 1.05 in primary meningioma and 0.85 in tumor recurrence. This corresponds to a specificity of 0.88 for the detection of higher tumor grading. Specificity was significantly higher in fasting compared to nonfasting subjects (0.96 versus 0.73; p < 0.025). SUV quantification lead to a reduced specificity of 0.77 at the same level of sensitivity. The only false-negative PET finding occurred in a recurrent meningioma, which had been operated on four times before.

CONCLUSION

Overnight fasting before injection is needed to improve the diagnostic accuracy of FDG-PET for noninvasive metabolic grading of meningioma. Hyperglycemia in nonfasting patients and in diabetic patients may lead to overestimation of meningioma grading.