NIMG-27. THE PROGNOSTIC VALUE OF FET PET IN PATIENTS WITH RECURRENT GLIOMA TREATED WITH BEVACIZUMAB

Abstract

Abstract BACKGROUND After multiple recurrences in glioma patients, bevacizumab is frequently used as salvage therapy. In this group of patients, we evaluated the prognostic value of amino acid PET using O-(2-[18F]fluoroethyl)-L-tyrosine (FET) before initiation of bevacizumab. METHODS We retrospectively identified adult glioma patients at recurrence with (i) at least one or more previous recurrences, (ii) who were treated with bevacizumab, and (iii) who underwent FET PET imaging before bevacizumab initiation. Maximum and mean tumor-to-brain ratios (TBRmax, TBRmean), metabolic tumor volume (MTV), and dynamic parameters (i.e., time-to-peak, slope) were obtained from FET PET. Additionally, contrast-enhancing volumes on MRI were calculated. Threshold values of imaging parameters for evaluating the prognosis were established by ROC analyses using overall survival (OS) of ≥ 6 months as reference. The prognostic value of imaging parameters was subsequently evaluated using the log-rank test and multiple logistic regression analyses. RESULTS Twenty-eight patients (glioblastoma, 96%) with a median of 2 recurrences (range, 1-5) were eligible for data evaluation. The patients received a median number of 7 bevacizumab cycles (range, 1-27). The static FET PET parameter TBRmean was the best parameter (threshold, 2.1; AUC, 0.78; P=0.014) to identify patients with a significantly longer OS (8.2 vs. 4.9 months; P=0.044). In contrast, the MTV, contrast-enhancing volume, and dynamic FET PET parameters were not significant. TBRmean remained significant in multiple logistic regression analysis (P=0.031), indicating an independent predictor for OS. CONCLUSION Our data suggest that static FET PET allows identifying patients with longer OS before initiation of bevacizumab.