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.