A Modified Tumor-Node-Metastasis Staging System for Colon Cancer Patients with Fewer than Twelve Lymph Nodes Examined

To construct a modified tumor-node-metastasis (TNM) staging system for stage I-III colon cancer patients with lymph nodes examined (LNE) < 12. The clinicopathological and survival data of 3870 stage I-III colon cancer patients with LNE < 12 from the Surveillance, Epidemiology, and End Results (SEER) database between 2010 and 2015 (development cohort) and 126 stage I-III patients with LNE < 12 from the Second Affiliated Hospital of Harbin Medical University between 2011 and 2015 (validation cohort) were identified. The optimal stratification of LNR for cancer-specific survival (CSS) was achieved using X-tile software. The predictive accuracy of the modified stage (mStage) was determined by the concordance index (C-index). The modified N stage (mN stage) was built based on the LNR (mN0: LNR = 0, mN1: 0 < LNR < 0.4 or cancer nodule formation and mN2: 0.4 ≤ LNR ≤ 1). Preferable C-indices could be found for mStage compared with TNM stage in both development (0.750 vs 0.727) and validation cohorts (0.682 vs 0.646). Besides, patients with mStage A and B diseases could not benefit from adjuvant chemotherapy, while in patients with mStage C-F diseases, those receiving radical surgery plus adjuvant chemotherapy presented better CSS than those with radical surgery alone. The mStage system could predict the prognosis of colon cancer patients with LNE < 12 accurately and showed superior predictive power compared with conventional TNM staging system. Moreover, adjuvant chemotherapy might play inequable roles in patients with different mStage diseases.