Heterogeneous survival between stage IIA and stage IIIA colon cancer when different numbers of lymph nodes are harvested

BACKGROUND: We aim to compare the prognosis between patients with stage IIA and stage IIIA colon cancer. METHODS: We analysed patients with stage IIA or stage IIIA colon cancer based on data from the US Surveillance, Epidemiology, and End Results (SEER) database. Survival data were generated as Kaplan-Meier curves and were compared by log-rank tests. A multivariate Cox proportional hazards model was used to analyze the risk factors. RESULTS: In total, 43 379 patients (38 784 stage IIA and 4595 stage IIIA) were included from the SEER database. A Kaplan-Meier analysis showed no significant difference between patients with stage IIA and IIIA colon cancer (P = 0.547). In the subgroup of patients with number of lymph nodes harvested (LNH) ≥12, a multivariate analysis showed that compared with stage IIA patients, stage IIIA patients were more likely to have a poorer cancer-specific survival (CSS) (hazard ratio (HR) 1.252, 95% confidence interval (CI) 1.095-1.431, P = 0.001). In the subgroup of patients with LNH <12, a multivariate analysis showed that compared with stage IIA patients, stage IIIA patients were more likely to have a better CSS (HR 0.820, 95% CI 0.731-0.919, P = 0.001). CONCLUSIONS: Patients with stage IIA colon cancer had a CSS comparable with that of patients with stage IIIA disease. When adequate lymph nodes were retrieved (LNH ≥12), stage IIA patients had a greater CSS than stage IIIA patients. On the contrary, when inadequate lymph nodes were retrieved (LNH <12), stage IIA patients had a poorer CSS than stage IIIA patients.