MBRS-25. GENOMIC ANALYSES REVEALED RADIATION-INDUCED GLIOBLASTOMA IN A SUBSET OF RECURRENT MEDULLOBLASTOMAS

Despite advances in medulloblastoma treatment and research, recurrent medulloblastoma is still devastating. Additionally, misidentification of secondary malignancy due to histological ambiguity leads to misdiagnosis and eventual inappropriate treatment. Through deep-sequencing of RNA and whole-exome of recurrent tumors from 17 pediatric medulloblastomas, we found that 3 patients had radiation-induced glioblastoma rather than recurrent medulloblastomas. We also uncovered that PDGFRA is a putative driver in radiation-induced glioblastoma, which gives an insight into the possible application of PDGFRA-targeted therapy. The observation of frequent gain of 7q region containing EZH2 accompanied by its high expression both in primary and recurrent medulloblastomas provides a clue to new a therapeutic target to prevent recurrence.