Sequential implementation of DSC-MR perfusion and dynamic [(18)F]FET PET allows efficient differentiation of glioma progression from treatment-related changes

PURPOSE: Perfusion-weighted MRI (PWI) and O-(2-[(18)F]fluoroethyl-)-l-tyrosine ([(18)F]FET) PET are both applied to discriminate tumor progression (TP) from treatment-related changes (TRC) in patients with suspected recurrent glioma. While the combination of both methods has been reported to improve the diagnostic accuracy, the performance of a sequential implementation has not been further investigated. Therefore, we retrospectively analyzed the diagnostic value of consecutive PWI and [(18)F]FET PET. METHODS: We evaluated 104 patients with WHO grade II–IV glioma and suspected TP on conventional MRI using PWI and dynamic [(18)F]FET PET. Leakage corrected maximum relative cerebral blood volumes (rCBV(max)) were obtained from dynamic susceptibility contrast PWI. Furthermore, we calculated static (i.e., maximum tumor to brain ratios; TBR(max)) and dynamic [(18)F]FET PET parameters (i.e., Slope). Definitive diagnoses were based on histopathology (n = 42) or clinico-radiological follow-up (n = 62). The diagnostic performance of PWI and [(18)F]FET PET parameters to differentiate TP from TRC was evaluated by analyzing receiver operating characteristic and area under the curve (AUC). RESULTS: Across all patients, the differentiation of TP from TRC using rCBV(max) or [(18)F]FET PET parameters was moderate (AUC = 0.69–0.75; p < 0.01). A rCBV(max) cutoff > 2.85 had a positive predictive value for TP of 100%, enabling a correct TP diagnosis in 44 patients. In the remaining 60 patients, combined static and dynamic [(18)F]FET PET parameters (TBR(max), Slope) correctly discriminated TP and TRC in a significant 78% of patients, increasing the overall accuracy to 87%. A subgroup analysis of isocitrate dehydrogenase (IDH) mutant tumors indicated a superior performance of PWI to [(18)F]FET PET (AUC = 0.8/< 0.62, p < 0.01/≥ 0.3). CONCLUSION: While marked hyperperfusion on PWI indicated TP, [(18)F]FET PET proved beneficial to discriminate TP from TRC when PWI remained inconclusive. Thus, our results highlight the clinical value of sequential use of PWI and [(18)F]FET PET, allowing an economical use of diagnostic methods. The impact of an IDH mutation needs further investigation. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00259-020-05114-0.