Racialized economic segregation and stage at diagnosis of colorectal cancer in the United States.

Purpose: In order to improve colorectal cancer outcomes in the United States, there is an urgent need for research on the drivers of geographic disparities in stage at diagnosis. Our objective was to determine the effects of racialized economic segregation on the odds of late diagnosis.

Methods: Among 187,843 adults (≥ 18 years old) with new diagnoses of colorectal cancer reported to the Surveillance, Epidemiology and End-Results program between 1st January 2009 and 31st December 2013, exposure to racialized economic segregation was measured at the county-level using Index of Concentration at the Extremes metrics. Multilevel logistic regression models including registry and county random effects were fit to examine the association between racialized economic segregation and odds of metastatic disease at time of diagnosis.

Results: Odds of late diagnosis were greatest in counties with the lowest compared to highest quintile for racial and economic privilege (OR 1.14; 95% CI 1.09-1.20). In multilevel models adjusting for individual-level covariates, odds of late diagnosis were greater for all patients except those living in counties with the highest concentration of white high-income individuals. There was significant effect modification of this relationship by age, with greater adverse effects for younger adults (OR 1.16; 95% CI 1.02-1.32) than older adults (OR 1.06; 95% CI 1.00-1.11). Racialized economic segregation was strongly associated with access to affordable healthcare.

Conclusions: Spatial social polarization, quantified in relation to racialized economic segregation, increases the odds of late diagnosis of colorectal cancer for persons residing in the least compared to most privileged counties.