“…Covariates included age at colon cancer diagnosis (<50, 50-59, 60-69, and >70 years), race/ethnicity (Non-Hispanic white, Non-Hispanic black, Hispanics and others) [20], health insurance (private insurance including Medicare with private supplement, Medicare/other public, Medicaid, and not insured), censustract residence (100% urban, 100% rural, and urban/rural mixed), census-tract population below the federal poverty level (<20% and >20%), census-tract adults with less than high school education (<25% and >25%) [21,22], census-tract population percentage of married (<50% and >50%) [23], tumor size (< 4 cm and > 4 cm) [24,25], lymph nodes retrieved (<12 and >12) [26], tumor grade (well/moderately differentiated, and poor/undifferentiated), Charlson comorbidity index (0, >1) [27], anatomic subsites (proximal, distal, and others) [28], colon cancer classi cation (only with colon cancer, multiple cancers with colon as the rst primary cancer, multiple cancers with colon as the non-rst cancer) [29], number of positive lymph nodes (continuous variable), and delayed chemotherapy (receiving chemotherapy > 8 weeks after surgery: yes and no) [30].…”