NIMG-84. PREDICTION OF RESPONSE TO LOMUSTINE-BASED CHEMOTHERAPY IN GLIOMA PATIENTS AT RECURRENCE USING MRI AND FET PET

Abstract BACKGROUND This study evaluates O-(2-[18F]fluoroethyl)-L-tyrosine (FET) PET and contrast-enhanced MRI for early response assessment in glioma patients at recurrence treated with lomustine-based chemotherapy. METHODS Thirty-six adult WHO CNS Grade 3 or 4 gliomas (glioblastoma, 69%) (median number of recurrences, 1; range, 1-3) were retrospectively identified. Besides MRI, serial FET scans performed baseline after chemotherapy initiation cycles, 2). Mean maximum tumor-to-brain ratios (TBR), metabolic tumor volumes (MTV), the occurrence new distant hotspots a mean TBR > 1.6 follow-up, dynamic parameter time-to-peak derived from all scans. Threshold values parameters defined using receiver operating characteristic analyses to predict progression-free survival (PFS) ≥ 6 months overall (OS) 12 months. was based on RANO criteria. Using univariate multivariate estimates, predictive value criteria subsequently evaluated. RESULTS After treatment initiation, median follow-up time 11 (range, 3-71 months). Relative changes TBR, MTV, predicted significantly longer PFS (all P< 0.003) OS 0.05). At (n≥ 1) worse outcome, shorter (P=0.001) (P< 0.001). Changes did not (P Multivariate revealed that had highest significance level non-response 0.001; hazard ratio, 8.578), independent criteria, IDH mutation status, O6-methylguanine-DNA-methyltransferase promoter methylation. CONCLUSIONS seems be powerful tool identifying responders initiation.