NI-08 Utility of multiple positron emission tomography tracers in the diagnosis of brain tumors according to the 2016 World Health Organization classification

Objective: Magnetic resonance imaging alone is not sufficient for the diagnosis and therapy outcomes in brain tumors. We herein examined the utility of positron emission tomography (PET) studies for diagnosis in brain tumors. Methods: Between April 2009 and June 2020, 320 patients with central nervous diseases, including 140, 65, 52, 52, and 11 patients with glioma, metastatic brain tumor, malignant lymphoma, meningioma, and demyelinating disease, respectively, underwent PET studies (FDG, MET, FLT, and FMISO) in our department. Lesion/normal (L/N) ratios for FDG, MET, and FLT and lesion/blood ratio (L/B ratio) for FMISO were compared. The glioma subtypes were compared based on the 2016 World Health Organization classification (IDH-mut, Codel, IDH-wt, GBM), and metastatic brain tumors, malignant lymphomas, meningiomas, and demyelinating diseases were compared with GBM. Results: In glioma, the cutoff MET L/N ratios to distinguish between IDH-mut and Codel, IDH-mut and GBM, Codel and GBM, and IDH-wt and GBM were 3.61, 4.42, 4.92, and 4.33, respectively, and the cutoff FLT L/N ratios to distinguish between IDH-mut and IDH-wt, IDH-mut and GBM, Codel and GBM, and IDH-wt and GBM were 3.43, 6.46, 3.39, and 7.56, respectively. The cutoff FDG and MET L/N ratios between metastatic brain tumors and GBM were 2.27 and 4.89; the cutoff FDG L/N and FMISO L/B ratios between malignant lymphoma and GBM were 4.68 and 2.13; and the cutoff FDG and MET L/N ratios between meningioma and GBM were 1.58 and 4.36. Demyelinating disease and GBM were distinguishable by FDG, MET, and FLT L/N ratios of 2.29, 3.32, and 5.85, and FMISO L/B ratio of 1.68. Conclusion: Four PET tracers were required to differentiate glioma subtypes. FDG and MET are useful for distinguishing GBM from metastatic brain tumor, malignant lymphoma, and meningioma, whereas accumulation was lower for all four PET tracers in demyelinating diseases than in GBM.