Comparisons Between PET With 11C-Methyl-l-Methionine and Arterial Spin Labeling Perfusion Imaging in Recurrent Glioblastomas Treated With Bevacizumab

Purpose The aim of this study was to clarify whether arterial spin labeling (ASL) perfusion imaging can assess biological effects from bevacizumab (BEV) therapy as reliably as PET with C-11-methyl-l-methionine (C-11-met-PET). Materials and Methods Twenty-four patients with recurrent glioblastoma were examined using both ASL and C-11-met-PET before and 4 and 8 weeks after starting BEV treatment. Tumor-to-normal brain (T/N) ratios, fluctuations in T/N ratio, and tumor volumes were compared between ASL and C-11-met-PET. Accuracy of predicting patient with long progression-free survival (PFS) was assessed for T/N ratios and fluctuations for ASL and C-11-met-PET in each phase and in each period using receiver operating characteristic curves. Between 2 groups of patients assigned by cutoff values from receiver operating characteristic curves, PFS was compared in each phase or in each period. Results T/N ratios, fluctuations in ratio, and tumor volumes correlated significantly between ASL and C-11-met-PET at all time points and all periods. Arterial spin labeling was eligible as a predictor for long PFS only in assessment of fluctuations in T/N ratio. However, the most accurate predictors for long PFS were T/N ratio from C-11-met-PET at 8 weeks and the fluctuation from baseline to 4 weeks in T/N ratio from C-11-met-PET. Conclusions Blood flows on ASL correlated with accumulations of C-11-met on PET in recurrent glioblastoma under BEV treatment. Although C-11-met-PET offered superior accuracy for predicting patients with long PFS from time points, ASL offered reliable prediction of long PFS, provided that fluctuations in T/N ratio between consecutive scans are assessed.