Dynamic 18F-FET PET is a powerful imaging biomarker in gadolinium-negative gliomas

Background. We aimed to elucidate the place of dynamic O-(2-[F-18]-fluoroethyl)-L-tyrosine (F-18-FET) PET in prognostic models of gadolinium (Gd)-negative gliomas. Methods. In 98 patients with Gd-negative gliomas undergoing F-18-FET PET guided biopsy, time activity curves (TACs) of each tumor were qualitatively categorized as either increasing or decreasing. Additionally, post-hoc quantitative analyses were done using minimal time-to-peak (TTPmin) measurements. Prognostic factors were obtained from multivariate hazards models.The fit of the biospecimen- and imaging-derived models was compared. Results. A homogeneous increasing, mixed, and homogeneous decreasing TAC pattern was seen in 51, 19, and 28 tumors, respectively. Mixed TAC tumors exhibited both increasing and decreasing TACs. Corresponding adjusted 5-year survival was 85%, 47%, and 19%, respectively (P < 0.001). Qualitative and quantitative TAC measurements were highly intercorrelated (P< 0.0001).TTPmin was longest (shortest) in the homogeneous increasing (decreasing) TAC group and in between in the mixed TAC group. TTPmin was longer in isocitrate dehydrogenase (/DH)-mutant tumors (P< 0.001). Outcome was similarly precisely predicted by biospecimen- and imaging-derived models. In the biospecimen model, World Health Organization (WHO) grade (P< 0.0001) and IDH status (P< 0.001) were predictors for survival. Outcome of homogeneous increasing (homogeneous decreasing) TAC tumors was nearly identical, with bothTTP(min) > 25 min (TTPmin <= 12.5 min) tumors and /DH-mutant grade II (/DH-wildtype) gliomas. Outcome of mixed TAC tumors matched that of both intermediate TTPmin (>12.5 min and <= 25 min) and /DH-mutant, grade III gliomas. Each of the 3 prognostic clusters differed significantly from the other ones of the respective models (P< 0.001). Conclusion. TAC measurements constitute a powerful biomarker independent from tumor grade and IDH status.