P03.02.A AMIDE PROTON TRANSFER-WEIGHTED (APTW) MRI IN CLINICAL ROUTINE FOR RESPONSE ASSESSMENT OF GLIOBLASTOMA

Abstract BACKGROUND Response assessment in Glioblastoma (GBM) poses significant challenges, particularly in the presence of therapy-related MRI changes, which can occur at any time point during and after treatment. A reliable diagnostic method for single time point detection and its differentiation from progressive disease (PD) would greatly benefit clinical management. This study evaluates the clinical utility and diagnostic performance of amide proton transfer-weighted (APTw) MRI in GBM response assessment. MATERIAL AND METHODS APTw MRI was integrated into routine clinical brain tumor imaging at our institution, yielding 870 scans from 626 patients. APTw signal intensity was assessed within contrast-enhancing (CE)-T1w and FLAIR regions of interest. Differences between PD and therapy related MRI changes were analyzed using unpaired t-tests, and diagnostic accuracy was evaluated through receiver operating characteristic (ROC) analysis. RESULTS A total of 260 MRI scans from 145 confirmed GBM, IDH wildtype (CNS WHO grade 4) were analyzed. The median APTw signal intensity was highest in CE-T1w regions of treatment-naïve GBM (preoperative MRI, n=49) at 2.54% (IQR: 2.22-2.88). Among 65 scans exhibiting PD (n=42) or therapy-related MRI changes (n=23), median APTw signal intensity was significantly higher in PD with 2.23% (IQR: 1.85-2.7) vs 1.76% (IQR: 1.07-1.97; p=0.001). ROC analysis across the entire cohort yielded an area under the curve (AUC) of 0.82, improving to 0.93 for scans within six months post-radiotherapy. Anti-angiogenic therapy reduced APTw contrast significantly (1.98% vs. 2.42%; p<0.0001). CONCLUSION APTw MRI can complement routine brain tumor imaging protocols and holds promise for supporting response assessment in GBM. However, its diagnostic accuracy in distinguishing therapy-related MRI changes decreases with the use of anti-angiogenic treatments and in later disease stages. These findings establish APTw MRI as a strong candidate for future prospective studies aimed at evaluating advanced imaging techniques, ideally through head-to-head comparisons, in glioma response assessment.