Abstract A074: Contribution of neighborhood and clinical factors to differences in early-onset colorectal cancer mortality across different racial and ethnic groups
Authors: Demb Joshua , Gomez Scarlett , Canchola Alison , Qian Alexander , Murphy James D. , Gupta Samir , Martinez Maria Elena 
Published: January 2023

Objectives: We investigated racial and ethnic differences in colorectal cancer (CRC) mortality in adults with early onset colorectal cancer (ages &lt;50; EO-CRC) in California and quantified the contribution of sociodemographic, health system, and clinical factors to racial and ethnic disparities in mortality. Methods: California Cancer Registry data were used to estimate CRC-specific mortality for adults ages 18-49 with EO-CRC between 2000-2019 for each racial/ethnic group (non-Hispanic Black [NHB], Hispanic, Asian American, American Indian/Alaska Native [AIAN], Native Hawaiian/Pacific Islander [NHPI]) compared with non-Hispanic White (NHW) adults. Additional disaggregated comparisons were conducted in Asian American ethnic groups: Chinese, Filipino, Japanese, Korean, South Asian, Southeast Asian, Other Asian and NHPI, compared to NHW individuals and separately using Chinese adults as a referent group. Cox proportional hazards models were used to measure association between race/ethnicity and CRC mortality risk, yielding unadjusted hazard ratios (HR) and adjusted hazard ratios (aHR) accounting for sociodemographic, clinical and health system factors, with corresponding 95% confidence intervals (95% CI). Mediation analyses were conducted to measure the percentage of contribution of factors to overall racial/ethnic CRC mortality rates using a sequence of multivariable Cox models. Results: There were 22,997 adults ages 18-49 with an EO-CRC diagnosis between 2000-2019, with 3,544 Asian (1,039 deaths), 6,889 Hispanic (1,998 deaths), 125 AIAN (36 deaths), 1,668 NHB (670 deaths), 10,473 NHW (3,089 deaths), 135 NHPI (51 deaths) and 163 (&lt;5 deaths) unknown race/ethnicity adults. Compared to NHW adults, higher CRC mortality was shown for NHPI adults (HR=1.69; 95% CI: 1.27-2.23; aHR=1.36; 95% CI: 1.03-1.79) and NHB adults (HR=1.53; 95% CI: 1.41-1.66; aHR=1.17; 95% CI: 1.07-1.29). Hispanic adults had an increased risk of CRC mortality in the unadjusted model (HR=1.15, 95% CI: 1.09-1.22) that was attenuated in the adjusted model (aHR=0.99, 95% CI: 0.92-1.04), compared to NHW adults. After disaggregating the Asian American group, Southeast Asian adults had increased CRC mortality risk in the unadjusted (HR=1.29, 95% CI: 1.13-1.46) but not adjusted model (aHR=1.10; 95% CI: 0.97-1.26), compared to NHW adults. In mediation analyses that examined contributors to the association between race/ethnicity and CRC mortality risk, neighborhood socioeconomic status and insurance status were among the top five most influential factors for Hispanic, NHB, and NHPI adults. However, the magnitude of influence differed by racial and ethnic group. Conclusions: Compared to NHWs, NHPI and NHB adults with EO-CRC had increased CRC mortality risk, even after adjusting for clinical and sociodemographic factors. Mediation analyses highlighted variation in the importance of various sociodemographic, clinical, health system and neighborhood factors, underscoring the need to better disentangle factors within racial and ethnic groups that contribute to disparities in CRC-related mortality.

Citation Format: Joshua Demb, Scarlett Gomez, Alison Canchola, Alexander Qian, James D. Murphy, Samir Gupta, Maria Elena Martinez. Contribution of neighborhood and clinical factors to differences in early-onset colorectal cancer mortality across different racial and ethnic groups [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr A074.