[18F]FET-PET/CT as a prognostic factor in newly-diagnosed gliomas II and III

1690 Objectives: Positron emission tomography (PET) using O-(2-[18F]fluoroethyl)-L-tyrosine has proven its value in brain tumor detection. The following study aims to investigate the prognostic value of amino acid metabolism in untreated gliomas grade II and III according to the new 2016 WHO classification. Material and Methods: In this single centre retrospective study a total of 36 patients (age range 23 - 84 y) with treatment-naive, histologically proven WHO grade II or III gliomas as defined by the 2016 WHO classification for CNS tumors were included. Static [18F]FET-PET was performed 20 minutes after i.v. tracer injection. Images were first visually assessed by two experienced nuclear medicine physicians, who were blinded to the diagnosis. Semi-quantitative analysis was performed using 2D regions of interest for both tumor and background (SUVmax, SUVmean). Standardized uptake values were used to gain tumor-to-background (TBR) ratios. Histological results, molecular markers (including IDH status and MGMT status) and outcome (in terms of progression-free [PFS] and overall survival [OS]) were correlated with PET parameters. Results: 14 patients with grade II (diffuse astrocytoma n=10, oligodrendroglioma n=4) and 22 patients with grade III gliomas (anaplastic astrocytoma n=15, anaplastic oligondendroglioma n=7) were included. Both IDH mutation and MGMT methylation proved as significant adverse prognostic factors regarding PFS (p