Quality and Location of the Surgical Episode Mediate a Large Proportion of Socioeconomic-Based Survival Disparities in Patients with Resected Stage I–III Colon Cancer

Introduction: Lower socioeconomic status (SES) is associated with shorter overall survival (OS) in patients with locoregional colon cancer. We aimed to estimate: (1) the proportion of SES-based OS disparities mediated by disparities in the quality and location of surgical treatment in patients with resected stage I–III colon cancer and (2) the relative importance of components of surgical quality. Patients and Methods: We examined patients ages 18–80 years with resected stage I–III colon adenocarcinoma using the 2010–2016 National Cancer Database. SES was defined at the zip code level. Inverse odds weighting mediation analysis was used to estimate the proportion mediated (PM) for nine treatment quality-related and facility-related factors and composite PMs in models including all nine mediators. Models compared high SES patients with each lower SES stratum. Results: Among 171,009 patients, 5-year OS increased from 70.4% in low SES patients to 78.1% in high SES. When high SES patients were compared with low, lower-middle, and upper-middle SES patients, PM ranges among lower SES strata were: minimally invasive surgery 16.0–16.6%, lymph nodes examined 7.7–9.6%, positive margins 3.8–6.5%, length of stay 16.7–28.1%, readmissions insignificant to 3.7%, treatment at > 1 CoC facility 2.7–3.1%, facility type insignificant to 7.3%, facility volume 2.9–8.2%, and adjusted facility 90-day mortality rates 33.2–42.8%. Composite PMs were 76.9% (95% CI 61.3%, 92.4%) for low SES, 68.7% (95% CI 56.4%, 81.1%) for lower-middle SES, and 60.9% (95% CI 43.1%, 78.6%) for upper-middle SES. Conclusions: These data suggest that improving the quality of the surgical episode for disadvantaged patients undergoing resection for locoregional colon cancer could decrease SES-based survival disparities by over half.