Usefulness of preoperative grading of primary brain tumors using F-18 FDG and C-11 methionine PET

Abstract

Objectives: On the determination of treatment for preoperative primary brain tumors, it is very important for the neurosurgeons to predict the grade of malignancy or the extent of the tumors. The aim of this study is to evaluate the usefulness of FDG PET and MET PET when considering the plan of operation for the primary brain tumors. Methods: We examined 12 patients with preoperative brain tumors who underwent FDG PET and MET PET. Moreover, we estimated the correlations between WHO grading and the tumor/normal brain uptake ratios (T/N ratio). Results: The T/N ratios of FDG in GIV were significantly higher than that in GII ( p<0.01) or GIII ( p<0.01), but there was not a significant difference in the T/N ratio between GII and GIII ( p=0.11). There was not a significant correlation between WHO grading and T/N ratio of MET. F/M ratio in GII was significantly lower than that in GIII ( p<0.05) or GIV ( p<0.05). Discussion: In a plan to treat glioma, it is very important to suppose its histology. In this study, FDG was useful for differentiating between glioblastoma (GIV) and other graded brain tumors (excluding malignant lymphoma). In regard to the use of MET PET, the tumors can be detected and differentiated with high sensitivity and good contrast. On the occasion of planning the operation, it may be helpful to comprehend the malignancy and the location of the tumors. Conclusions: FDG PET was useful for grading the primary brain tumor, especially differentiating between glioblastoma and the other brain tumors. MET PET was not useful for evaluating the grade but was sensitive to detect the location. A combination of FDG PET with MET PET is very useful as an auxiliary examination when neurosurgeons are deciding on the treatment strategy.