Ventricle Contact Is Associated With Higher 11C Methionine PET Uptake in Glioblastoma

Abstract Introduction: Ventricle contact is associated with a worse prognosis and more aggressive tumor characteristics in glioblastoma (GBM). This is hypothesized to be a result of neural stem cells located around the lateral ventricles, in the subventricular zone. 11C methionine Positron Emission Tomography (metPET) is an indicator for increased proliferation, as it shows uptake of methionine, an amino acid needed for protein synthesis. This study is the first to study metPET characteristics of GBM in relation to ventricle contact. Methods: 12 patients with IDH wild type GBM a were included. Using MRI, the following regions were determined: primary tumor (defined as contrast enhancing lesion on T1) and peritumoral edema (defined as edema visible on FLAIR excluding the enhancement). PET parameters in these areas were extracted using PET fused with MRI imaging. Parameters extracted from the PET included: maximum and mean tumor-to-normal ratio (TNRmax and TNRmean) and metabolic tumor volume (MTV). Results: TNRmean of the primary tumor showed significantly higher values for the ventricle contacting group compared to the non-contacting group (4.44 vs 2.67, p=0.015). Other metPET parameters suggested higher values for the ventricle contacting group, but these differences did not reach statistical significance. Conclusion: GBM with ventricle contact show a higher methionine uptake and thus increased proliferation compared with GBM without ventricle contact. This might explain survival differences and should be considered in treatment decisions.