Diagnostic yield of simultaneous dynamic contrast-enhanced magnetic resonance perfusion measurements and [ 18 F]FET PET in patients with suspected recurrent anaplastic astrocytoma and glioblastoma

Purpose Both amino acid positron emission tomography (PET) and magnetic resonance imaging (MRI) blood volume (BV) measurements are used in suspected recurrent high-grade gliomas. We compared the separate and combined diagnostic yield of simultaneously acquired dynamic contrast-enhanced (DCE) perfusion MRI and O-(2-[ 18 F]-fluoroethyl)-L-tyrosine ([ 18 F]FET) PET in patients with anaplastic astrocytoma and glioblastoma following standard therapy. Methods A total of 76 lesions in 60 hybrid [ 18 F]FET PET/MRI scans with DCE MRI from patients with suspected recurrence of anaplastic astrocytoma and glioblastoma were included retrospectively. BV was measured from DCE MRI employing a 2-compartment exchange model (2CXM). Diagnostic performances of maximal tumour-to-background [ 18 F]FET uptake (TBR max ), maximal BV (BV max ) and normalised BV max (nBV max ) were determined by ROC analysis using 6-month histopathological ( n = 28) or clinical/radiographical follow-up ( n = 48) as reference. Sensitivity and specificity at optimal cut-offs were determined separately for enhancing and non-enhancing lesions. Results In progressive lesions, all BV and [ 18 F]FET metrics were higher than in non-progressive lesions. ROC analyses showed higher overall ROC AUCs for TBR max than both BV max and nBV max in both lesion-wise (all lesions, p = 0.04) and in patient-wise analysis ( p < 0.01). Combining TBR max with BV metrics did not increase ROC AUC. Lesion-wise positive fraction/sensitivity/specificity at optimal cut-offs were 55%/91%/84% for TBR max , 45%/77%/84% for BV max and 59%/84%/72% for nBV max . Combining TBR max and best-performing BV cut-offs yielded lesion-wise sensitivity/specificity of 75/97%. The fraction of progressive lesions was 11% in concordant negative lesions, 33% in lesions only BV positive, 64% in lesions only [ 18 F]FET positive and 97% in concordant positive lesions. Conclusion The overall diagnostic accuracy of DCE BV imaging is good, but lower than that of [ 18 F]FET PET. Adding DCE BV imaging did not improve the overall diagnostic accuracy of [ 18 F]FET PET, but may improve specificity and allow better lesion-wise risk stratification than [ 18 F]FET PET alone.