BT-4 PROGNOSIS OF HISTOLOGICALLY DIAGNOSED GRADE 2-3 IDH-WILD TYPE DIFFUSE GLIOMAS TREATED WITH RADIATION AND TEMOZOLOMIDE

<jats:title>Abstract</jats:title> <jats:p>Although adult diffuse gliomas, IDH-wildtype, histologically diagnosed as grade 2-3 have been regarded as clinically equivalents with glioblastomas, the prognosis of this population has scarcely been discussed with further consideration of treatment backgrounds. This retrospective study aimed to investigate the prognosis of adult patients with IDH-wildtype diffuse gliomas histologically diagnosed as WHO grade 2-3 using a cohort with homogenous treatment background. A total of 214 IDH-wildtype cases were extracted from the collected data of the previous study investigating the prognostic significance of molecular markers (Arita, Acta Neuropathol Commun 2016). The inclusion criteria were as follows: supratentorial tumor, pretreatment Karnofsky Performance status of 70 or higher, wildtype-H3.3 status, chemoradiation therapy with temozolomide after the initial surgery. Overall survival (OS) and progression free survival (PFS) were evaluated by Kaplan-Meier methods. The histological diagnosis in this study was made based on the WHO 2016 classification, and the histological criteria is compatible with the current classification (CNS WHO5).The mean age was 62.8, 59.8 and 60.2 years in grade 2 (n=8), 3 (n=45) and 4 (n=161) case, respectively. The higher ratio of biopsy cases was associated lower grades (50% in grade 2, 22% in grade 3 and 9% in grade 4 cases). Grade 2-3 cases showed short survival (OS 24.7 months and PFS 9.7months) despite the intensive treatment of chemoradiation at the time of diagnosis. In details, OS was 41.5, 23.1 and 17.8 months in grade 2, 3 and 4 cases, respectively. PFS was 12.6, 9.7 and 8.2 months in grade 2, 3 and 4 cases, respectively. Our results revealed that IDH-wildtype grade 2-3 cases showed dismal prognosis even after the chemoradiation at the time of diagnosis. Further development of treatments is needed in this population as well as glioblastomas, IDH-wildtype.</jats:p>