Diagnostic yield of simultaneous dynamic contrast-enhanced magnetic resonance perfusion measurements and [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-[F]-fluoroethyl)-L-tyrosine ([F]FET) PET in patients with anaplastic astrocytoma and glioblastoma following standard therapy.

Methods: A total of 76 lesions in 60 hybrid [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 [F]FET uptake (TBR), maximal BV (BV) and normalised BV (nBV) 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 [F]FET metrics were higher than in non-progressive lesions. ROC analyses showed higher overall ROC AUCs for TBR than both BV and nBV in both lesion-wise (all lesions, p = 0.04) and in patient-wise analysis (p < 0.01). Combining TBR with BV metrics did not increase ROC AUC. Lesion-wise positive fraction/sensitivity/specificity at optimal cut-offs were 55%/91%/84% for TBR, 45%/77%/84% for BV and 59%/84%/72% for nBV. Combining TBR 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 [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 [F]FET PET. Adding DCE BV imaging did not improve the overall diagnostic accuracy of [F]FET PET, but may improve specificity and allow better lesion-wise risk stratification than [F]FET PET alone.