Optimal examined lymph node count in node-negative colon cancer should be determined

Background: We aimed to investigate the association between optimal examined lymph node (ELNs) and overall survival to determine the optimal cutoff point. Methods: Cox models and locally weighted scatterplot smoothing were used to fit hazard ratios and explore an optimal cutoff point based on the Chow test. Results: Overall survival increased significantly with the corresponding increase in the number of ELNs after adjusting for covariates. In Chow's test, the optimal cutoff point for node-negative colon cancer was 15, which was validated in both cohorts after controlling for confounders (Surveillance, Epidemiology, and End Results database: hazard ratio: 0.701, p < 0.001; single-center: HR: 0.563; p = 0.031). Conclusions: We conservatively suggest that the optimal number of ELNs for prognostic stratification is 15 in node-negative colon cancer.Lay abstract Over the past 20 years, the number of examined lymph nodes (ELNs) has been an important indicator to accurately assess lymph node metastasis, and therefore, many studies have focused on exploring an optimal cutoff point to prevent missed detection of positive lymph nodes. However, in recent years, ELNs has been considered to play other key roles. In the current study, ELNs were deemed an important prognostic factor, and the minimum number of ELNs was recommended to be 15 in node-negative colon cancer via rigorous statistical methods and a large sample of data.