GE-36MOLECULAR-GENETIC AND CLINICAL CHARACTERISTICS OF THE "ASTROCYTIC" GLIOMAS WITH TOTAL 1p19q LOSS

BACKGROUND: Although 1p19q codeletion is associated with better response to therapy and longer survival in oligodendroglial gliomas, molecular-genetic and clinical characteristics of "astrocytic" gliomas with codeletion have not been well elucidated at the moment. METHODS: We collected 57 gliomas with total 1p19q loss from among 183 gliomas of WHO grade II or III surgically treated in Keio University Hospital between 1990 and 2010. Those tumors were classified to oligodendroglial or "astrocytic" gliomas by institutional diagnosis based on WHO criteria of each times. Chromosomal copy number abberation (CNA, by comparative genomic hybridization (CGH)), IDH 1/2 mutation, and promoter methylation of MGMT were assessed. Survival outcome was compared between two histological groups. Since criteria of oligodendroglial tumor has changed overtime, analyses have also been performed after histopathological re-assessment by a single pathologist with the current criteria. RESULTS: 57 codeleted gliomas included 37 oligodendroglial, 16 astrocytic, and 4 unclassified low-grade gliomas by institutional diagnosis. By CGH, gain on 11q was specifically detected in oligodendroglial tumors. Gain on chromosome 7 and loss on 10p were more frequent in "astrocytic" gliomas. Frequency of IDH gene mutations and MGMT methylation was similary high in the two histological groups. Kaplan-Meier curves for overall survival (OS) of the patients with codeleted oligodendroglial and "astrocytic" tumors overlapped, and median OS was 175 and 170 months, respectively. Analyses after histopathological re-assessment by a single pathologist showed almost identical results. CONCLUSIONS: "Astrocytic" gliomas with 1p19q codeletion are likely to have comparable biological characteristics to codeleted oligodendroglial gliomas.