18FET-PET UPTAKE DYNAMICS SERVES AS AN ADDITIONAL IMAGING BIOMARKER IN ASTROCYTOMAS WITH IDH1/2 MUTATION AND NO LOH1p/19q

Stratification of glial tumors according to the presence of molecular features such as IDH1/2 mutation and loss of heterozygosity 1p/19q is gaining importance for tumor classification and treatment. In analogy, metabolic imaging such as 18FET-PET uptake dynamics reflected by time-to-peak (TTP) analysis allows discrimination between high-risk and low-risk glioma. The present study aims to investigate whether TTP offers additional prognostic information within this framework of molecular signature. 300 patients with a de-novo glioma WHO grade II-IV and 18FET-PET imaging at initial diagnosis were grouped according to IDH1/2 mutation and LOH 1p/19q status: IDH1/2 wildtype (wt) and IDH1/2mutant with or without co-deletion 1p/19q. Clinical and imaging factors such as age, Karnofsky Performance status, treatment and median TTP were analyzed for association with progression-free and overall survival (PFS and OS). 255 out of 300 (85%) patients showed 18FET-PET uptake. Molecular profile concerning IDH1/2 mutation and LOH 1p/19q status was available in 238 patients. The subgroup with IDH1/2 mutation and LOH 1p/19q had the best outcome concerning PFS and OS compared to IDH1/2 mutant /no LOH 1p/19q and IDH wt patients (p<0.0001 for PFS and OS). Median TTP values within the three subgroups were 12.5 minutes in the IDH 1/2 wt tumors and 25 min in both IDH 1/2 mutant tumors with/without LOH 1p/19q. TTP gained additional prognostic information in gliomas with IDH1/2mutation without LOH 1p/19q (p=0.03 for OS/PFS). 18FET-PET derived dynamic analysis using TTP delivers additional prognostic information concerning both progression-free and overall survival in the “astrocytic” subgroup of tumors with IDH1/2 mutation and no LOH 1p/19q. Thus, 18FET-PET uptake dynamics may serve as an additional imaging biomarker beyond the molecular signature.