Tumor mutational burden and driver mutations: Characterizing the genomic landscape of pediatric brain tumors

Background Tumor mutational burden (TMB) and driver mutations are potential biomarkers to guide targeted therapy selection. Malignant gliomas with high TMB in children may preferentially benefit from treatment with immune checkpoint inhibitors (ICPIs). Higher TMB may relate to lower incidence of driver mutations, but this relationship has not been studied in pediatric brain tumors. Procedure Comprehensive genomic profiling was performed on 723 pediatric (≤21 years) brain tumor samples using DNA extracted from formalin‐fixed paraffin‐embedded tissue. TMB was calculated as mutations per megabase and categorized as low (0‐6), intermediate (6‐20), or high (>20). Analysis included 80 clinically relevant driver mutations; genomic alterations known to confer a selective growth advantage. Results Of 723 brain tumors, TMB was low in 91.8%, intermediate in 6.1%, and high in 2.1%. In the high TMB cohort, 93% of tumors harbored a driver mutation; 70% and 63% in the intermediate and low TMB cohorts, respectively (P