Socioeconomic disparities in survival outcomes among children with non-metastatic Ewing sarcoma treated on upfront Children’s Oncology Group clinical trials.

10041 Background: Poverty is emerging as an adverse risk factor for relapse and death across many pediatric cancers. Socioeconomic disparities have not been comprehensively investigated in Ewing sarcoma. We leveraged Children’s Oncology Group (COG) data to investigate socioeconomic disparities in survival outcomes in children with non-metastatic Ewing sarcoma treated on upfront phase III clinical trials from 2001-2005 and 2010-2017. Methods: This was a retrospective cohort study of US patients aged 0-21 years with non-metastatic Ewing sarcoma enrolled on COG AEWS0031 and AEWS1031. The analytic cohort was restricted to participants with complete data on exposures and covariates. Poverty was the primary exposure of interest, defined at the household (sole means-tested public insurance) and neighborhood (census-defined high-poverty ZIP code with ≥20% of population below 100% Federal Poverty Level) levels. Cox proportional hazards regression models evaluated associations between poverty exposures, event-free survival (EFS), and overall survival (OS) from time of trial enrollment. Multivariable models adjusted for age (as a continuous variable), sex, race/ethnicity (non-Hispanic White vs Other), initial tumor volume (≤200 ml vs > 200 ml), primary disease site (pelvic/non-pelvic/extraosseous), and assignment to interval compressed chemotherapy (yes/no). Results: Among 551 complete cases, 23% (n = 128) were household poverty-exposed and 19% (n = 106) were neighborhood poverty-exposed. Median age at trial enrollment was 12 years; median event-free follow-up time was 8.7 years. In multivariable models, household poverty-exposed children experienced a 52% increased hazard of EFS-event compared to unexposed children (adjusted hazard ratio [aHR] 1.52, 95% CI 1.03, 2.26, p = 0.04), and a 64% increased hazard of death compared to unexposed (aHR 1.64, 95% CI 1.03, 2.62, p = 0.04). Neighborhood poverty-exposure was not associated with increased hazard of EFS or OS event. Conclusions: Household poverty, as proxied by public insurance, is an adverse risk factor for EFS-event and death among children and young adults with non-metastatic Ewing sarcoma despite standardized treatment on national clinical trials. Investigation of mechanisms driving these disparities—including treatment delays and differential local control approaches—is ongoing. These data highlight an immediate need to evaluate poverty-targeted interventions alongside new therapeutic agents to improve outcomes.