BIOM-29. THE PROGNOSTIC AND PREDICTIVE SIGNIFICANCE OF PARTIAL MGMT PROMOTER METHYLATION FOR IDH-WILDTYPE GLIOBLASTOMA PATIENTS

Abstract BACKGROUND Glioblastoma patients showing hypermethylation of the promoter O6-methylguanine-methyltransferase (MGMT) gene have significantly improved survival when treated with temozolomide compared to hypomethylated MGMT promoters. However, prognostic and predictive significance partial methylation is unclear. METHODS The National Cancer Database was queried for newly diagnosed in 2018 histopathologically-confirmed IDH-wildtype glioblastoma. status correlated overall (OS) using multivariable Cox regression Bonferroni correction multiple testing (p< 0.008 significant). RESULTS 3,663 were identified diagnosed, glioblastoma known methylation. Of 2,807 who received single agent chemotherapy (i.e. likely temozolomide), unmethylated, partially methylated, hypermethylated, methylated not otherwise specified (NOS) 57.9%, 5.0%, 3.1%, 34.0% cases, respectively, later group consisting predominantly hypermethylated cases. Multivariable analysis demonstrated that among receiving temozolomide, those unmethylated promoters had worse OS than (hazard ratio (HR) 1.94; 95% confidence interval (CI), 1.54-2.44; p< 0.001). (HR 1.02; CI, 0.72-1.46; p=0.9) NOS 0.99; 0.78-1.26; p=0.928) statistically different from patients. CONCLUSIONS their counterparts, supporting use therapy these