DISP-18. RACIAL DISPARITY IN THE UTILIZATION OF MOLECULAR DIAGNOSTIC AS A PROXY FOR SUB-OPTIMAL CLINICAL CARE IN GLIOBLASTOMA PATIENTS

Abstract BACKGROUND Molecular characterization of IDH mutation and MGMT-promoter methylation (MGMTm) are standard-of-care (SOC) diagnostics and essential to diagnosis, treatment, and prognosis of glioblastomas. Here, we determined the extent to which racial disparity occurs in this dimension of oncologic care. METHODS 31,439 glioblastoma patients were derived from the National Cancer Database (NCDB,2018-2021), with 20,736 IDH-wildtype patients with defined MGMT-status. Accessibility to SOC diagnostics was defined as whether patients got IDH/MGMT testing or not. Race/Ethnicity was grouped into Non-Hispanic White (NHW), Non-Hispanic Black, Asian/Pacific Islander, Hispanic, and Others. Receipt of SOC diagnostics and treatments, post-operative outcomes, and overall survival (OS) were explored using multivariable logistic regression, Kaplan-Meier method, and Cox proportional hazards models. RESULTS Relative to NHWs, all racial minority groups were less likely to have undergone IDH or MGMT-testing. These effects remain robust after adjusting for economic status, insurance, and facility type. Patients who received neither IDH nor MGMT-testing were 38% less likely to undergo SOC concurrent chemo-/radiation therapy (cCRT) relative to those having both testing. Further, patients having neither IDH nor MGMT-testing showed significantly higher risk of 30-day mortality (aOR:2.20), 90-day mortality (aOR:1.60), and hazard of death (median OS:8.9-mon,aHR:1.09,p=0.002) than those having both testing (median OS:12.9-mon). Of those tested for both IDH/MGMT, the odds of bearing a methylated MGMT-promoter remained relatively constant across five racial groups. Non-NHW glioblastomas patients were significantly less likely to receive SOC-modality. Of the patients who underwent IDH/MGMT-testing and cCRT, median OSs were 23.7 and 14.4-mon for MGMT-methylated and unmethylated glioblastoma, respectively. No significant difference in hazards of death for racial/ethnic minorities compared to NHWs was detected, regardless of MGMT-methylation status. CONCLUSIONS Our findings suggest that non-NHW glioblastoma patients are less likely to undergo SOC diagnostic (IDH/MGMT) testing, which serves as a proxy for receipt of sub-optimal clinical care. For glioblastoma patients who underwent SOC molecular testing and treatment, survival is similar across racial groups.