The Impact of Racial Residential Segregation on Colorectal Cancer Outcomes and Treatment

Objective: We sought to examine the impact of racial residential segregation on Black-White disparities in colorectal cancer diagnosis, surgical resection, and cancer-specific survival. Summary Background Data: There are clear Black-White disparities in colorectal cancer diagnosis and treatment with equally disparate explanations for these findings, including genetics, socioeconomic factors, and health behaviors. Methods: Data on Black and White patients with colorectal cancer were obtained from SEER between 2005 and 2015. The exposure of interest was the index of dissimilarity (IoD), a validated measure of segregation derived from 2010 Census data. Outcomes included advanced stage at diagnosis (AJCC stage IV), resection of localized disease (AJCC stage I-II), and cancer-specific survival. We used Poisson regression with robust error variance for the outcomes of interest and Cox proportional hazards were used to assess cancer-specific 5-year survival. Results: Black patients had a 41% increased risk of presenting at advanced stage per IoD [risk ratio (RR) 1.41, 95% confidence intervals (CI) 1.18, 1.69] and White patients saw a 17% increase (RR 1.17, 95%CI 1.04, 1.31). Black patients were 5% less likely to undergo surgical resection (RR 0.95, 95%CI 0.90, 0.99), whereas Whites were 5% more likely (RR 1.05, 95%CI 1.03, 1.07). Black patients had 43% increased hazards of cancer-specific mortality with increasing IoD (hazard ratio (HR) 1.43, 95%CI 1.17, 1.74). Conclusions: Black patients with colorectal cancer living in more segregated counties are significantly more likely to present at advanced stage and have worse cancer-specific survival. Enduring structural racism in the form of residential segregation has strong impacts on the colorectal cancer outcomes.