Abstract
494
Background: Within the updated 2016 WHO classification, gliomas are stratified into separate molecular genetic entities. Among these subgroups, IDH-mutant, 1p/19q-codeleted gliomas (oligodendrogliomas) exert a favorable outcome compared to IDH-wildtype tumors such as glioblastoma. With this regard, treatment regimens have to be chosen carefully and the individual risk of treatment-associated morbidity has to be weight up. However, the role of dynamic 18F-FET PET as independent prognostic biomarker in oligodendroglioma still remains unknown and was therefore evaluated.
Methods: Patients with histologically verified de-novo oligodendroglioma (IDH-mutant and 1p/19q-codeleted) received MRI and dynamic 18F-FET PET prior to any further therapy. 18F-FET PET parameters (maximum/mean tumor-to-background ratio [TBRmax, TBRmean], minimal time-to-peak [TTPmin], biological-tumor-volume [BTV]), contrast-enhancement in MRI, the Karnofsky-Performance-Score (KPS), age and the consecutive application of surgical procedures were assessed and correlated with the clinical outcome in terms of progression-free survival (PFS) as defined by Response-Assessment in Neuro-Oncology criteria (RANO) using Kaplan-Meier estimates and uni-/multivariate analyses.
Results: Seventy-six patients with de-novo oligodendroglioma (WHO grade II n=58, WHO grade III n=18) were included. During a median follow-up time of 67.5 months, 43/78 patients experienced tumor progression. Overall, the median PFS was 57.0 months. In the univariate analyses, WHO grade (WHO grade II vs. III: median PFS 64.0 vs. 39.0 months, p=0.035) and TTPmin in dynamic PET (≤25 vs. >25 min: median PFS 50.0 vs. 104.0 months, p=0.021) were associated with the clinical outcome. In contrast, age, contrast enhancement in MRI, KPS, TBRmax/mean and BTV were not associated with PFS (p>0.05). In multivariate analysis, both WHO grade (hazard ratio 2.4 (CI: 1.2-4.9), p=0.019) and TTPmin(hazard ratio 2.4 (CI: 1.1-5.2), p=0.021) remained significant prognostic factors with regard to PFS.
Conclusions: Within the molecular genetic group of oligodendroglioma, TTPmin in dynamic 18F-FET PET represents an independent prognostic imaging biomarker for PFS. Therefore, the evaluation of dynamic 18F-FET PET in addition to histological and molecular genetic features might help to individualize the patient management and decision making.