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

Background To construct a modified tumor-node-metastasis (TNM) staging system for stage I-III colon cancer patients with lymph nodes examined (LNE) < 12. Methods 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). Results 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. Conclusions 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.

Automated summary

A modified TNM staging system was constructed for stage I-III colon cancer patients with lymph nodes examined less than 12, using lymph node ratio to predict prognosis accurately. The mStage system showed superior predictive power compared to the conventional TNM staging system in predicting cancer-specific survival for these patients.