OTHR-28. Multi-institution analysis of tumor mutational burden and outcomes in pediatric CNS tumor patients

Abstract

Abstract Pediatric CNS tumors are the leading cause of pediatric cancer mortality. Research addressing genomic biomarkers and clinical outcomes is needed to inform therapeutic decision making. Tumor mutational burden (TMB) has been correlated with decreased survival across cancer types. This study is the first to examine TMB and outcomes in pediatric CNS tumor patients across multiple academic medical centers. We conducted a retrospective analysis of 121 pediatric patients (61 female (50%)) with a median age of 9 diagnosed with a primary CNS tumor at Albany Medical Center, Roswell Park Comprehensive Cancer Center, Upstate University Hospital, or University of Rochester Medical Center from 2008 to 2021. Common tumor types included low-grade glioma (N=51), high-grade glioma (N=30), medulloblastoma (N=11), ependymoma (N=7), ganglioglioma (N=4), and 18 other CNS tumors. Seventy-one patients had driver-mutations, including TP53 inactivation (n=17), BRAF-KIAA1549 fusion (n=16), FGFR1 amplification (n=12), BRAF V600E mutation (n=12), NF1 loss (n=12), and H3F3A K28M mutation (n=6). TMB data was available for most patients (N=91), median TMB was 1 mutations/megabase (mut/Mb, range=0-132). There were 26 deaths observed; patients with high TMB (≥3 mut/Mb; N=35) as compared to patients with low TMB (<3 mut/Mb; N=56) were more likely to have a death event, 43% (N=15) vs 9% (N=5), respectively. High TMB tumors were more frequently high-grade (77%) than low-grade (41%). High TMB tumors were more frequently treated with systemic therapy (86%) compared to low TMB tumors (70%). Tumor progression was more common in high TMB (71%) than in low TMB tumors (54%). This multi-institutional analysis suggests that high TMB is correlated with higher rates of progression and death as compared to low TMB tumors. Knowledge of these findings is critical for identifying patients who may benefit from alternative treatments, such as immunotherapies.