A national evaluation of adjuvant chemotherapy in pT4N0M0 colon cancer from the National Cancer Database

T stage is a prognostic biomarker for overall survival in colon cancer and pathologic T4 disease is a high-risk characteristic. Adjuvant chemotherapy is recommended to improve overall survival in pT4N0M0, but compliance with guidelines is unknown. We aimed to evaluate adjuvant chemotherapy use and impact on overall survival in pT4N0M0 colon cancer.

The National Cancer Database was reviewed for pT4N0M0 colon adenocarcinomas undergoing curative surgical resection (2010-2017). Cases were stratified into no adjuvant chemotherapy and adjuvant chemotherapy cohorts. Moderated multiple regression assessed factors associated with no AC. Kaplan-Meier and Cox regression assessed overall survival in propensity-score matched cohorts. The main outcome measures were adjuvant chemotherapy use, factors associated with adjuvant chemotherapy, and impact on overall survival.

Of 11 847 cases, 62.4% (n = 7391) received no adjuvant chemotherapy. With private insurance, comorbidities or income do not affect adjuvant chemotherapy use. Medicare cases with a Charlson-Deyo comorbidity index of 0 (odds ratio [OR] = 0.861, 95% confidence interval [CI] = 0.760 to 0.975; P = .019) and Medicare payors with high income (OR = 0.813, 95% CI = 0.690 to 0.959; P = .014) were associated with adjuvant chemotherapy. Medicaid Charlson-Deyo comorbidity index 0 (OR = 1.374, 95% CI = 1.125 to 1.679; P = .002) and uninsured Charlson-Deyo comorbidity index 0 (OR = 1.351, 95% CI = 1.120 to 1.629; P = .002) were associated with no adjuvant chemotherapy. Adjuvant chemotherapy was associated with improved 5-year overall survival (71.7% vs 56.4%; P < .001; adjusted hazard ratio = 0.543, 95% CI = 0.499 to 0.590; P < .001).

Although adjuvant chemotherapy is associated with improved overall survival, compliance is low. There is a complex relationship between payor, income, comorbidity, and adjuvant chemotherapy receipt. Medicare patients with no comorbidities or higher income have better adjuvant chemotherapy use. With private insurance, adjuvant chemotherapy compliance is not affected by comorbidities or income, whereas Medicaid and uninsured patients with no comorbidities have poor compliance. Future work could target these disparities for equitable care.