JS09.8.A COMPARATIVE PROGNOSTIC VALUE OF O-(2-[18F]-FLUOROETHYL)-L-TYROSINE PET IMAGING AND DCE MRI BLOOD VOLUME IMAGING IN PATIENTS WITH SUSPECTED RECURRENT IDH-WILDTYPE HIGH-GRADE GLIOMA

Abstract BACKGROUND Quantitative blood volume (BV) imaging using dynamic T1-weighted contrast enhanced (DCE) perfusion MRI may be of diagnostic value in patients with suspected recurrent high-grade glioma, but the association of DCE BV measurements with survival is not known. The aim of the study was to compare the prognostic information of DCE BV measurements with that of O-(2-[18F]-fluoroethyl)-L-tyrosine ([18F]FET) PET imaging in treated IDH wildtype high-grade astrocytoma and glioblastoma (2016 WHO classification). MATERIAL AND METHODS A total of 94 hybrid [18F]FET PET/MRI scans with DCE from unique adult patients were retrospectively analysed. Scans were obtained after surgery/biopsy (n=94) and radiotherapy (n=93) due to variable suspicion of residual or progressive disease. In each scan the visually BV positive (VOLBV), the [18F]FET PET avid (VOLFET) and the contrast-enhancing (VOLCE) volumes were delineated, and fractional tumour volumes (fVOL) within VOLCE, as well as maximal BV (BVmax) and maximal [18F]FET tumour-to-background ratio (TBRmax) were determined. Accuracy for prediction of 6-month progression free survival and 1 year overall survival were assessed by logistics regression. Associations with overall survival were assessed for each parameter by Cox proportional hazard analysis. RESULTS In a univariate analysis, adjusted for age and MGMT, both VOLCE, and all [18F]FET and DCE BV derived metrics were predictive of both 6 month progression free survival, 1 year survival and overall survival. ROC AUC for prediction of 6 month progression free survival and 1 year overall survival tended to be higher for [18F]FET derived metrics, but ROC AUC values were not significantly different between any [18F]FET and DCE BV derived metrics. In Cox models for overall survival (adjusting for age, MGMT and VOLCE) only TBRmax and VOLBV had independent prognostic value among [18F]FET PET and DCE BV derived metrics, respectively. In a final model including both TBRmax and VOLBV, only TBRmax remained significant.. CONCLUSION DCE BV and [18F]FET PET derived metrics provides prognostic information independent of age, MGMT status and contrast enhancing tumour volume in treated glioblastoma, with volume of increased BV and [18F]FET TBRmax providing strongest associations with overall survival. Accounting for functional imaging biomarkers may be important in balancing future randomized clinical trials.