Molecular biomarker testing to predict outcomes in gliomas: A SEER registry study in Kentucky.

e14095 Background: Molecular testing has been required since 2021 for the diagnosis of many primary CNS tumors, and in 2018 US cancer registries implemented molecular site-specific data items. With increasing approval of targeted therapies, molecular testing is essential for improving outcomes. We reviewed biomarker completeness in a population-based registry in Kentucky to assess integration of molecular testing into practice and its impact on survival. Methods: We analyzed first primary brain tumors diagnosed from 2018 to 2023 from the Kentucky Cancer Registry, a SEER registry. Using Brain Molecular Markers (Data Item #3816), biomarker completeness was categorized as complete (codes 01-09), not applicable (code 85, information not collected), or incomplete (codes 87, 99, missing). Markers examined included IDH, 1p/19q co-deletion, and MGMT methylation. Descriptive statistics were used to compare patients’ characteristics by completion status. Log-rank tests were performed to assess the significant differences by molecular marker status for glioblastoma, diffuse astrocytoma, and oligodendroglioma separately; case number, median and one-year survival are reported. Results: In 1,802 cases of primary brain tumors, 62.5% had complete biomarkers, 15.5% not applicable, and 22.0% incomplete. Complete cases were predominantly high-grade (87.7%) and glioblastoma (74.7%). Incomplete cases were more frequent from 2018-2020 (54.8%), age ≥65 (51.5%), and non-glioblastoma (55.3%). Among cases where molecular testing was not applicable, over half were young 0-19 (51.4%) with low-grade tumors (44.4%). In glioblastoma, incomplete coding demonstrated worse survivals (N=175, median 2.6 mo, 16.7% 1-yr survival) versus IDH-wildtype (N=841, 9.1 mo, 40.9%, respectively). For oligodendroglioma, IDH-mutant/1p/19q co-deleted had excellent prognosis (N=92, median not reached, 97.8% 1-yr survival) versus incomplete (N=8, 50.0% 1-yr survival). For diffuse astrocytoma, IDH-mutant demonstrated superior survival (N=79, median not reached, 94.9%) while incomplete (N=28, median 50.3 months, 67.9%) fared worse. All between-group comparisons were statistically significant (log-rank p<0.05). Conclusions: Cases not having molecular testing are common and have worse outcomes. Our findings demonstrate primary brain tumor patients would benefit from a widespread initiative to increase molecular testing to ensure correct diagnosis and treatment.