Uptake Characteristics On Dynamic F-18-Fet Pet In Glioblastoma Are Not Associated With The Tert-Promoter Mutational Status

1536 Objectives: The current molecular genetic stratification of gliomas is based on the isocitrate dehydrogenase (IDH)-mutational status and 1p/19q-codeletion. In addition, the mutation of the ‘telomerase reverse transcriptase gene promoter’ (TERTp) has been identified as an important factor for individual prognostication and potentially within tumorgenesis. As uptake characteristics on dynamic 18F-FET PET have been shown to be a prognostic factor as well, we aimed to analyse whether minimal-time-to-peak (TTPmin) on dynamic PET is associated with TERTp-mutation. Methods: Patients with de-novo IDH-wildtype glioblastoma, WHO grade IV, available TERTp-mutational status and dynamic 18F-FET PET scan prior to any therapy were included. The maximal and mean tumor-to-background-ratios (TBRmax/TBRmean), the biological-tumour-volume (BTV) and minimal-time-to-peak (TTPmin) on dynamic PET were analysed and correlated with the TERTp-mutational status. Results: One hundred IDH-wildtype glioblastoma patients were included; 85/100 of the analysed tumors showed a TERTp-mutation (C228T or C250T), 15/100 were classified as TERTp-wildtype. Median TBRmax (3.41 vs. 3.32, p=0.362), TBRmean (2.09 vs. 2.02, p=0.349) and BTV (26.1 vs. 22.4 ml, p=0.377) were independent of the TERTp-mutation. Moreover, TTPmin on dynamic PET was also comparable between those two groups (12.5 vs. 12.5 min, p=0.411). Between the TERTp-mutational subgroups (i.e. C228T (n=23) & C250T (n=62)), the median TBRmax (3.33 vs. 3.69, p=0.095), TBRmean (2.08 vs. 2.09, p=0.352), BTV (25.4 vs. 30.0 ml, p=0.130) and TTPmin (12.5 vs. 12.5 min, p=0.190) were comparable. Conclusions: Static and dynamic uptake characteristics of IDH-wildtype glioblastoma on 18F-FET PET are not associated with the TERTp-mutation. This supports dynamic 18F-FET PET as an independent prognostic information in addition to the TERTp-mutation, which has to be validated in future studies.