RADI-10. RADIOGENOMIC CORRELATION OF THE NEWLY PROPOSED MOLECULAR CHARACTERISATION OF GLIONEURONAL TUMOURS OF THE BRAIN

Abstract AIM: Stone et al. recently published the molecular characterisation of glioneuronal tumours, classifying them into 2 groups based upon methylation and expression profiles: Group 1 predominantly with BRAF and Group 2 predominantly with FGFR1 mutations. Our aim was to study differentiating neuroimaging features between these two groups on the same patient cohort to develop a neuroradiological assessment tool-kit. METHODOLOGY As the first step, an unblinded review of the presentation MRI scans was conducted by two Paediatric Neuroradiologists (KM and AP) to evaluate for discerning radiological features between the two groups. A tool-kit emerged following this consensus read. A third Paediatric Neuroradiologist (WJ) then blinded to the molecular subgrouping classified the cohort radiologically using this tool-kit to validate its accuracy. RESULTS MR imaging on 31 patients was reviewed (15-group 1 and 16-group 2). The tool-kit showed the following distinguishing assessment categories: (1) Tumour margins: ill-defined in 100% group 1, well-circumscribed in 100% group 2 tumours; (2) FLAIR-rim: present in 0% group 1, 88% group 2; 3) Location: temporal lobe in 80% group 1, extra-temporal in 75% group 2; 4) Enhancement patterns- Hazy, ‘out-of-focus’ enhancement in 73% group 1 tumours, half of group 2 tumours showed enhancement and it was well-defined; 5) Extension to the ependymal margin: present in 69% group 2 tumours. When this tool-kit was employed by the third neuroradiologist blinded to the molecular diagnoses, 90% accuracy was achieved. CONCLUSIONS We were able to develop a validated neuroradiological tool-kit to differentiate between the two major genetically-defined subgroups of glioneuronal tumours.