A Novel Mgmt Methylation-Based Prognostic Score In Patients With Glioblastoma.

2048Background: The methylation status of the O6-methylguanine-DNA methyltransferase (MGMT) promoter has been associated with improved outcome in glioblastoma (GBM) patients (pts). Pyrosequencing (PSQ) has been reported to be an accurate method for quantitative detection of CpG islands (CpGs) methylation, but the role of methylation heterogeneity among different CpGs sites is still unclear. Aim of this study was to evaluate on a large multicentric cohort a novel prognostic score based on the evaluation of the MGMT promoter methylation at 10 different CpGs sites. Methods: We retrospectively analyzed a series of 185 pts with GBM treated at the University Hospital of Udine and Istituto Oncologico Veneto in Padua between 2006 and 2015. The methylation level of 10 CpGs (74 – 83) was determined by PSQ. The cut-off point of 9% was used to define a CpG as methylated. One point was assigned to each methylated CpG, with a total score from 0 (all CpGs u003c 9%) to 10 (all CpGs ≥ 9%). A threshold capable to detect a favo...