10094-MPC-8 MOLECULAR PATHOLOGICAL ANALYSIS OF RADIATION-INDUCED GLIOBLASTOMA AFTER PEDIATRIC CEREBELLAR MEDULLOBLASTOMA TREATMENT

Abstract INTRODUCTION The number of long-term survivors of pediatric medulloblastoma has been increasing due to improved treatment options. However, secondary cancer can be an issue for long-term survivors. We report the molecular pathological evaluation of two cases of radiation-induced glioblastoma. Patients: Of the 27 patients with cerebellar medulloblastoma treated at our institution, two who were 3 years old and 11 years old at the time of medulloblastoma diagnosis and both were girls, developed cerebellar glioblastomas after the initial treatment at five years and 11 months and 22 years and eight months, respectively. These two cerebellar glioblastomas were clinically diagnosed as radiation-induced secondary cancer. RESULTS Both of the two cases we clinically diagnosed as radiation-induced glioblastoma had negative IDH-1, EGFR expression and positive p53 expression in immunohistochemistry. DISCUSSION It has been reported that EGFR expression is negative as a molecular feature of radiation-induced glioblastoma, and the two cases we experienced were consistent with radiation-induced secondary cancers. In general, primary glioblastoma is positive for EGFR expression in the supratentorial region and negative in the infratentorial region. Therefore, in the case of supratentorial glioblastoma, it is useful to evaluate EGFR expression to distinguish primary glioblastoma from secondary glioblastoma.