THE IMPACT OF RESIDENTIAL SEGREGATION ON COLORECTAL CANCER DIAGNOSIS AND TREATMENT
Michael Poulson, Department of Surgery, Boston Medical Center, Boston, MA
Background: There are well documented disparities in black-white colorectal cancer outcomes. We sought to examine the effects of racial residential segregation on the diagnosis, management, and outcomes of black colorectal cancer patients.
Methods: Black patients with colorectal cancer residing in the 50 most populous counties participating in the Surveillance, Epidemiology and End Results (SEER) program were identified between 2005 and 2015. County demographics and socioeconomic characteristics were obtained from the 2010 decennial Census and the 2013 5 year estimates of the American Community Survey (ACS). The racial index of dissimilarity (IoD), a validated proxy of racial segregation, was used to assess the evenness with which white and black residents are distributed across census blocks within each county. Multivariable analyses were performed predicting advanced stage at diagnosis (AJCC stage IV) in the overall cohort and for the resection of localized disease (AJCC stage I-II). County level covariates included county level proportion of population uninsured, proportion unemployed, and the Gini index (a validated measure of income inequality). Patient level covariates included sex and age at diagnosis. Cox proportional hazards was used to assess the relationship between residential segregation and the overall mortality in colorectal cancer.
Results: In total, 33,006 black patients with colorectal cancer were identified over the 10 year period. Median IoD was 0.641 (IQR0.619-0.771) in the overall cohort. On multivariable analysis, increasing index of dissimilarity was significantly associated with advanced stage at diagnosis (OR, 1.73; 95% CI, 1.20-2.49; p=0.003). Increasing segregation was also associated with a significant lesser likelihood of undergoing surgery for localized disease (OR 0.063, 95% CI, 0.050-0.081; p<0.001). For all cause mortality, residential segregation had no significant difference on hazards among black patients (HR 1.23; 95% CI, 0.921-1.645; p=0.160).
Conclusion: Black patients with colorectal cancer living in more segregated counties are significantly more likely to be diagnosed at an advanced stage and less likely to undergo resection for resectable disease, regardless of socioeconomic status. However, there was no observed effect of residential segregation on overall survival among black patients. These data suggest that enduring structural racism and resultant neighborhood characteristics have strong impacts on the timing of colorectal cancer diagnosis and access to appropriate surgical consultation. Evidence based policy reform, particularly in more segregated areas, is important in alleviating these black-white disparities in colorectal cancer.
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