BackgroundThe purpose was to examine the effect of nonmetastatic lymph nodes number (NLN) on survival in stage III colon cancer. To reduce the interference of acute inflammation, we included patients with stage III colon cancer who had undergone elective surgery and excluded those who had tumor perforation, obstruction, ischemia, or massive tumor bleeding.MethodsThis retrospective cohort study included 2244 patients with stage III colon cancer between 1995 and 2016 at a single center. The

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... of NLN on 5-year relapse-free survival (RFS), 5-year overall survival (OS), and comparison of multivariate factors was assessed according to tumor locations.ResultsThe two optimal cutoff values of NLN for proximal and distal colon, namely 27 and 12, were determined by plotting the time-dependent receiver operating characteristic curve. Overall, 499 of 891 and 1020 of 1353 patients with right-side and left-side colon cancer, respectively, had high NLN. In right-side colon cancer, patients with high NLN (≥ 27) had superior OS (74.9% vs. 62.7%, P< 0.001) and RFS (75.0% vs. 61.9%, P< 0.001) than did those with low NLN. Moreover, in left-side colon cancer, patients with high NLN (≥12) experienced significantly superior OS (80.8% vs. 68.6%, P< 0.001) and RFS (77.3% vs. 66.2%, P< 0.001) than did those with low NLN. Among the different subgroups of stage III colon cancer, the high NLN group showed significantly superior RFS and OS in stage IIIB (RFS: 77.0% vs. 68.0%, P= 0.001; OS: 78.6% vs. 67.9%, P< 0.001) and IIIC (RFS: 58.2% vs. 44.1%, P= 0.001; OS: 65.7% vs. 51.1%, P< 0.001) colon cancer. However, in stage IIIA colon cancer, high NLN only showed survival benefit in OS (91.5% vs. 89.8%, P= 0.041). Multivariate analyses confirmed that high NLN, high carcinoembryonic antigen (≥ 5ng/mL) level, and stage IIIC status are three independent prognostic factors in both the proximal and distal colon.ConclusionsNLN is a crucial prognostic factor for stage III colon cancer in various tumor locations or in the subgroups of stage III disease. In advanced stage III colon cancer, the importance of NLN and its role in anti-cancer immune response could be highlighted.