Effect of Metastatic to Examined Lymph Nodes Ratio on Colon Cancer SurvivalIntroduction The number of lymph nodes examined in colon cancer surgery varies widely. The current staging system is based on the number of metastatic lymph nodes (N1: metastatic lymph nodes ≤ 3, N2: metastatic lymph nodes ≥ 4) and does not consider any variations of the number of lymph nodes examined. Therefore, a ratio-based staging system has been proposed. The aim of this study is to evaluate the metastatic to examined lymph node ratio (LNR) as a prognostic factor in stage III colon cancer. Methods Retrospective review of the Automated Central Tumor Registry of the Department of Defense was performed. There were 1,286 stage III colon cancer patients who underwent curative surgical resections. Cases were divided into quartiles by LNR (0.01-0.11 vs. 0.12-0.22 vs. 0.23-0.45 vs. 0.46-1.00). Effects of the LNR on colon cancer survival were analyzed using a Kaplan Meier survival curve and Cox proportional hazard model. Results Decreasing LNR was found to be associated with improved survival in colon cancer patients. Five year-overall survival was 68%, 65%, 56%, and 39% for the lowest to the highest quartiles (p < 0.001). Multivariate analysis identified age, sex, tumor grade, tumor T stage, tumor N stage, and LNR as prognostic factors. Cox proportional hazard analysis identified LNR as a better prognostic factor compared with conventional lymph node staging for stage III colon cancer. Conclusion The metastatic to examined lymph node ratio is an excellent prognostic indicator in stage III colon cancer patients. This ratio-based staging system may provide more comparable prognostic information for colon cancer patient outcome.