MDB-18. MOLECULARLY-DEFINED MEDULLOBLASTOMA: POPULATION-LEVEL PATTERNS IN THE UNITED STATES, 2018-2019

Medulloblastoma is one of the most common types of brain and other CNS tumors among the pediatric population in the US. Molecularly-defined brain tumor histopathologies—including medulloblastoma subtypes—were incorporated into US cancer registry reporting for individuals with brain tumors beginning in 2018. We assessed the epidemiology and overall survival (OS) patterns for medulloblastoma in children and adolescents, highlighting molecularly-defined subtypes. Children and adolescents (0-19 years) that were histopathologically diagnosed with medulloblastoma from 2018-2019 and had brain molecular marker data were identified within the Commission on Cancer’s National Cancer Database (NCDB) and Central Brain Tumor Registry of the United States databases, which combines data from CDC’s National Program of Cancer Registries (NPCR) and NCI’s Surveillance, Epidemiology, and End Results (SEER) Programs. Incidence rates per 100,000 population with 95% confidence intervals (95CI) were estimated for histopathologies with ≥16 cases. One-year OS was estimated using NCDB data for histopathologies with ≥50 cases with follow-up through 2020 using Kaplan-Meier methods. There were 601 cases of histopathologically-confirmed medulloblastoma diagnosed in children and adolescents from 2018-2019, 39.6% of which had available molecular subtype information. Overall incidence of medulloblastoma was 0.37 (95CI=0.34-0.40). Incidence of medulloblastoma subtypes was 0.05 (95CI=0.04-0.06) for SHH-activated & TP53wt, 0.02 (95CI=0.01-0.02) for WNT-activated, 0.08 (95CI=0.06-0.09) for nonWNT/nonSHH, while SHH-activated & TP53mut was too rare to calculate incidence. One-year OS for all medulloblastoma was 96.6% (95CI=92.1%-100.0%). One-year OS for nonWNT/nonSHH was 96.6% (95CI=92.8%-100.0%), and for SHH-activated & TP53wt was 93.7% (95CI=87.1%-100.0%). Other subtypes occurred too rarely to calculate survival. Our findings provide the initial US epidemiological estimates for molecularly-defined medulloblastoma histopathologies in children and adolescents. As improvements in collection completeness lead to increased molecular subtype availability, the robustness of these estimates will increase. Collection of these data are essential for understanding the epidemiology of this important childhood and adolescent brain tumor.