Grading and outcome prediction of pediatric diffuse astrocytic tumors with diffusion and arterial spin labeling perfusion MRI in comparison with 18F-DOPA PET

PURPOSE: The aim of this study was to investigate MRI-derived diffusion weighted imaging (DWI) and arterial spin labeling (ASL) perfusion imaging in comparison with 18F-dihydroxyphenylalanine (DOPA) PET with respect to diagnostic performance in tumor grading and outcome prediction in pediatric patients with diffuse astrocytic tumors (DAT).

METHODS: We retrospectively analyzed 26 children with histologically proven treatment naïve low and high grade DAT who underwent ASL and DWI performed within 2 weeks of 18F-DOPA PET. Relative ASL-derived cerebral blood flow max (rCBF max) and DWI-derived minimum apparent diffusion coefficient (rADC min) were compared with 18F-DOPA uptake tumor/normal tissue (T/N) and tumor/striatum (T/S) ratios, and correlated with World Health Organization (WHO) tumor grade and progression-free survival (PFS). Statistics included Pearson's chi-square and Mann-Whitney U tests, Spearman's rank correlation, receiver operating characteristic (ROC) analysis, discriminant function analysis (DFA), Kaplan-Meier survival curve, and Cox analysis.

RESULTS: A significant correlation was demonstrated between rCBF max, rADC min, and 18F-DOPA PET data (p < 0.001). Significant differences in terms of rCBF max, rADC min, and 18F-DOPA uptake were found between low- and high-grade DAT (p ≤ 0.001). ROC analysis and DFA demonstrated that T/S and T/N values were the best parameters for predicting tumor progression (AUC 0.93, p < 0.001). On univariate analysis, all diagnostic tools correlated with PFS (p ≤ 0.001); however, on multivariate analysis, only 18F-DOPA uptake remained significantly associated with outcome (p ≤ 0.03), while a trend emerged for rCBF max (p = 0.09) and rADC min (p = 0.08). The combination of MRI and PET data increased the predictive power for prognosticating tumor progression (AUC 0.97, p < 0.001).

CONCLUSIONS: DWI, ASL and 18F-DOPA PET provide useful complementary information for pediatric DAT grading. 18F-DOPA uptake better correlates with PFS prediction. Combining MRI and PET data provides the highest predictive power for prognosticating tumor progression suggesting a synergistic role of these diagnostic tools.