Abstract A056: Assessment of environmental injustice in racial disparities of colorectal cancer mortality in metropolitan Detroit

Abstract Non-Hispanic Black (NHB) patients face the highest colorectal cancer (CRC) mortality rates in the US, heavily influenced by social determinants of health (SDOH). Neighborhood quality, a key SDOH, impacts both socioeconomic factors and exposure to cancer-related environmental contaminants. Thus, in studying the role of environmental justice on health outcomes it is crucial to account for the separate and combinatory effects of environmental and socioeconomic burden. The Centers for Disease Control and Prevention (CDC) created a comprehensive socio- environmental variable available at the census tract level called the Environmental Justice Index (EJI). The EJI utilizes 36 environmental, social, and health factors grouped into modules. We analyzed the EJI's social vulnerability module (SVM), environmental burden module (EBM), and the combined Social Environmental Score (SER) to assess the role of environmental injustice in CRC mortality by race. Patient data including census tract at diagnosis, demographics, and clinical features were obtained from the Metropolitan Detroit Cancer Surveillance System population-based cancer registry for 9727 NHW and 3778 NHB invasive CRC cases. The EJI SVM, EBM, and SER variables were linked to patients by census tract and converted to quartile-level variables, and mortality risk was evaluated for quartile 4 (highest burden) compared to quartile 1 (lowest burden). Cox proportional hazards regression, adjusting for demographics and clinical features, was used to estimate survival associations. We evaluated associations overall and stratified by race (Non-Hispanic White NHW, NHB) and age of onset (50, 50+). In nearly all models, we found all EJI variables increased the risk of mortality, with Hazard Ratios (HR) ranging from 1.02-2.89. SVM showed stronger effects overall compared to EBM, and most models showed similar effects among race and age groups in both overall and cancer-specific mortality. A notable exception to this was that NHB early onset (EO) patients showed an elevated risk of cancer-specific mortality due to EBM (HR=2.05, 95% Confidence Interval (CI)=1.21-3.45, p=0.019) compared to SVM (HR = 1.05, 95% CI = 0.58-1.88, p=0.88), and also compared to all EO EBM (HR=1.34, 95% CI=1.04-1.72, p=0.025) and NHW EO EBM (HR=1.25, 95% CI=0.83-1.89, p=0.29) patients. Additionally, cancer-specific mortality of EO patients with colon tumors specifically was highly elevated in both the EBM (HR=2.10, 95% CI=1.19-3.68, p=0.010) and SER (HR=2.89, 95% CI=1.55-5.36, p = 0.00081) models compared to all other groups and models. These results suggest that the combination of socio- environmental burdens contributes to racial disparities in CRC mortality in metropolitan Detroit, largely driven by social rather than environmental factors, except among NHB EOCRC where environmental factors appear to play a stronger role. Further analyses investigating the molecular implications of these exposures are needed to better understand the biological mechanisms driving tumor progression related to disparities among age and race. Citation Format: Natalie G Snider, R. B. Buchalter, Theresa Hastert, Gregory Dyson, Carina Gronlund, Elena Stoffel, Laura Rozek, Ed Peters, Ann Schwartz, Kristen Purrington. Assessment of environmental injustice in racial disparities of colorectal cancer mortality in metropolitan Detroit abstract. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr A056.