MBCL-51. RETROSPECTIVE ANALYSIS OF VICTORIAN PATIENTS DIAGNOSED WITH MEDULLOBLASTOMA BETWEEN 1990-2017

Abstract BACKGROUND Medulloblastoma is the most common yet challenging paediatric brain tumour. No longer considered a single disease entity, medulloblastoma is comprised of at least four distinct genetically and molecularly defined subgroups. OBJECTIVES Retrospectively assess the performance and outcomes of all patients diagnosed with medulloblastoma between 1990-2017 according to molecular subgroups. METHODS After obtaining ethical approval, confirming sample adequacy, 76 samples (FFPE and Fresh Frozen) were retrieved from the two Victorian children’s oncology providers, Monash Children’s Hospital and The Royal Children’s Hospital. Blinded review of histology and immunohistochemistry using subgroups specific antibodies (INI1, CTNNB1, GAB, YAP, DKK1, SFRP1), is performed by a neuropathologist. For molecular determination of the subgroups, DNA extraction and restoration (FFPE samples only), and bisulphite modification is performed prior to analysis on the Infinium MethylationEPIC BeadChip, containing >850k methylation sites, performed at the Australian Genome Research Facility. Whilst several methods exist, Methylation Array is the current gold standard for subgroup analysis. Data analysis is performed using the Heidelberg groups (MolecularNeuropathology) algorithm and locally using R-studio. Molecular information is paired with clinical variables and international data (where available). RESULTS 24 samples analysed to date show no discrepancy with regards to incidence amongst subgroups, gender distribution, outcomes and international data. Further analysis will examine trends in mutational burden within subgroups, change in population trends with respect to incidence, relapse and survival. Acknowledgements: CCF, Australian Lions, Baileys Day.