Background: Socioeconomic status (SES) has been associated with worse outcomes in stage III colon cancer. However, these studies have used large geographic areas (zip codes or counties) as a proxy for SES which may bias results. To overcome this challenge, we used a national database with census-tract level SES to assess the impact on cancer-specific (CSS) and overall survival (OS). Methods: Using the SEER Census-Tract Dataset from 2004-2015, we identified 8^th edition AJCC stage III colon adenocarcinoma patients who underwent curative-intent surgery and initiated adjuvant chemotherapy. The predictor variable was census-tract level SES, consisting of 7 variables such as income, housing, and education. SES was analyzed as quartiles. Statistical analysis included chi square tests for association and Kaplan-Meier and Cox regression for survival analysis. Results: We identified 27,222 patients who met inclusion criteria. Lower SES was associated with younger age, Black or Hispanic race/ethnicity, Medicaid or uninsured status, higher T stage, <12 lymph nodes examined and lower grade tumors. Median CSS was not reached; the 25^th percentile CSS time was 54 months for the lowest SES (LSES) quartile and 80 months for the highest (HSES). Median OS was 113 months for LSES and not reached for HSES. The 5-year CSS rate was 72.4% for the LSES quartile compared to 78.9% in the HSES (p<0.001). The 5-year OS rate was 66.5% for LSES and 74.6% in the HSES (p<0.001). After adjusting for potential confounders (age, sex, race, insurance, pathologic T and N stage and grade), LSES was associated with increased cancer-specific death relative to the HSES (HR 1.22; 95% CI [1.114-1.327]) Conclusions: This is the first study to evaluate CSS and OS in a national cohort of stage III colon cancer patients using a granular, standardized measure of SES. Despite receipt of guideline-based treatment, low SES remained a predictor of increased cancer-specific mortality. These data suggest that investigating treatment barriers beyond adjuvant therapy is needed to address colon cancer survival disparities.

Model adjusted for age, sex, race, insurance status, grade, and pathologic T and N stage