Disentangling Racial, Ethnic, and Socioeconomic Disparities in Treatment for Colorectal Cancer.

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Colorectal cancer is curable if diagnosed early and treated properly. Black and Hispanic patients with colorectal cancer are more likely to experience treatment delays and/or receive lower standards of care. Socioeconomic deprivation may contribute to these disparities, but this has not been extensively quantified. We studied the interrelationship between patient race/ethnicity and neighborhood socioeconomic status (nSES) on receipt of timely appropriate treatment among patients with colorectal cancer in California. White, Black, and Hispanic patients (26,870) diagnosed with stage I-III colorectal cancer (2009-2013) in the California Cancer Registry were included. Logistic regression models were used to examine the association of race/ethnicity and nSES with three outcomes: undertreatment, >60-day treatment delay, and >90-day treatment delay. Joint effect models and mediation analysis were used to explore the interrelationships between race/ethnicity and nSES. Hispanics and Blacks were at increased risk for undertreatment [Black OR = 1.39; 95% confidence interval (CI) = 1.23-1.57; Hispanic OR = 1.17; 95% CI = 1.08-1.27] and treatment delay (Black/60-day OR = 1.78; 95% CI = 1.57-2.02; Hispanic/60-day OR = 1.50; 95% CI = 1.38-1.64) compared with Whites. Of the total effect (OR = 1.15; 95% CI = 1.07-1.24) of non-white race on undertreatment, 45.71% was explained by nSES. Lower nSES patients of any race were at substantially higher risk for undertreatment and treatment delay, and racial/ethnic disparities are reduced or eliminated among non-white patients living in the highest SES neighborhoods. Racial and ethnic disparities persisted after accounting for neighborhood socioeconomic status, and between the two, race/ethnicity explained a larger portion of the total effects. This research improves our understanding of how socioeconomic deprivation contributes to racial/ethnic disparities in colorectal cancer.