PATH-09. CLINICAL CHARACTERISTICS AND MOLECULAR CHARACTERISTICS OF 244 MEDULLOBLASTOMAS IN JAPAN

Abstract BACKGROUND Medulloblastomas are at least classified into four core subgroups, including WNT-activated, SHH-activated, group 3 and group 4. These molecular subgroups have been introduced in the WHO classification, which has become fundamental and indispensable. The JPMNG is co-organized by the Japan Society for Neuro-Oncology and the Japanese Society for Pediatric Neurosurgery, and we have summarized clinical and molecular characteristics of Japanese MBs. METHODS We enrolled 267 cases of medulloblastoma from 44 centers participating in the JPMNG study. Central histopathological diagnosis was performed by three neuropathologists, and molecular genetic diagnosis was performed by NanoString nCounter system or DNA methylation array, and their single nucleotide mutations and copy number aberrations have been also examined. RESULTS A total of 244 cases were finally analyzed, and the 4-subgroup classification was WNT: 39 (16%), SHH: 61 (25%), group3: 42 (17%), and group4: 102 (41.8%), respectively. In cases of less than 3 years old, no WNT have been found and 62.2% cases were SHH. In cases of WNT-MB, the majority being children (6-18 years) (31/39: 79.5%), and 8 cases (8/39: 20.5%) in adults older than 18 years. In cases between 3 to 17 years old, Group 4 is the most (48.6%), and these trends is almost consistent with published. references. Metastatic or MYC gain Group 3 MBs were poor prognosis, while Group 4 MBs with loss of chromosome 11 or whole chromosomal aberration were good prognosis. CONCLUSIONS Clinical and molecular characteristics of Japanese WBT-MB were almost consistent with those reported in other countries, and the relationship between molecular properties and prognosis of group3/group4 MBs were also reproducible. These findings suggest importance of molecular properties of MBs are preserved beyond ethnic differences, and will contribute to develop new therapeutic strategies.