Among the MRI-suspected LGG, kinetic but not conventional analysis of FET uptake enabled remarkably high sensitivity for detection of HGG. This held true even for lesions with low or diffuse tracer uptake. Lesions with reduced tracer uptake must be interpreted with caution, as they can also harbour HGG tissue.

(18)F-FET PET has a high sensitivity for the detection of high-grade brain tumors. Its specificity, however, is limited by passive tracer influx through a disrupted blood-brain barrier and (18)F-FET uptake in nonneoplastic brain lesions. Gliomas show specific tracer uptake in the absence of CE on MRI, which most likely reflects biologically active tumor.

OBJECTIVE The aim of this prospective longitudinal study was to identify static and dynamic O-(2-[(18)F]fluoroethyl)-l-tyrosine PET ((18)FET-PET)-derived imaging biomarkers in patients with glioblastoma (GBM). METHODS Seventy-nine patients with newly diagnosed GBM were included; 42 patients underwent stereotactic biopsy (unresectable tumors) and 37 patients microsurgical tumor resection. All patients were scheduled to receive radiotherapy plus concomitant and adjuvant temozolomide (RCx/TMZ). (18)FET-PET evaluation using static and dynamic analysis was done before biopsy/resection, after resection, 4 to 6 weeks following RCx, and after 3 cycles of TMZ. Endpoints were survival and progression-free-survival. Prognostic factors were obtained from proportional hazards models. RESULTS Biological tumor volume before RCx (BTVpreRCx) was the most important (18)FET-PET-derived imaging biomarker and was independent of MGMT promoter methylation and clinical prognostic factors: patients with smaller BTVpreRCx had significantly longer progression-free and overall survival (OS). (18)FET time-activity curves (TACs) before treatment and their changes after RCx were also related to outcome; patients with initially increasing TACs experienced longer OS. CONCLUSION BTVpreRCx and TAC represent important (18)FET-PET-derived imaging biomarkers in GBM. Increasing TACs are associated with prolonged OS. The BTVpreRCx is a strong prognostic factor for progression-free survival and OS independent of the mode of surgery. Our data furthermore suggest that patients harboring resectable GBM might benefit from maximal PET-guided tumor resection. Originally published at: Suchorska, B; Jansen, N L; Linn, J; Kretzschmar, H; Janssen, H; Eigenbrod, S; Simon, M; Pöpperl, G; Kreth, F W; la Fougere, C; Weller, M; Tonn, J C (2015). Biological tumor volume in 18FET-PET before radiochemotherapy correlates with survival in GBM. Neurology, 84 (7)