Metabolic Ratio of FDG-PET and Histologic Grading in Cerebral Gliomas

ABSTRACT

To assess the degree of malignancy in cerebral gliomas at the time of diagnosis, we compared the metabolic ratio using 18F-fluorodeoxyglucose(FDG)-Positron Emission Tomography(PET) with histologic grading and proliferative index(Ki-67) of cerebral gliomas. Materials for this study were histologically-examined 21 gliomas and they were divided into glioblastomas as group 1, anaplastic gliomas as group 2, and low-grade gliomas as group 3. The visual analysis of FDG-PET images showed hypermetabolic lesions in 14(87.5%) out of 16 high-grade gliomas (glioblastomas and anaplastic gliomas), and hypometabolic lesions in 4(80%) out of 5 low-grade gliomas. Tumor to cerebellum ratio(T/Cbll) in FDG-PET was used as metabolic ratio and the values of T/Cbll in each group were 1.30+/-0.10, 0.73+/-0.07, 0.70+/-0.07, respectively. In comparision of T/Cbll between group 1 with remaining two groups, differences were statistically significant(p=0.0002, p=0.0002, respectively), however, there was no statistical difference between group 2 and group 3. The values of Ki-67 were 24.16+/-5.66 in group 1, 8.10+/-2.70 in group 2, 5.46+/-1.23 in group 3, and differences were statistically significant between group 1 and group 2, 3(p=0.015, p=0.015, respectively), but there was no statistical difference between group 2 and group 3. The correlation between T/Cbll and Ki-67 was good and statistically significant(p=0.0047). In conclusion, the visual and semiquantitative analysis of FDG-PET would be helpful in determining the degree of malignancy in cerebral gliomas.