TNM Staging of Colorectal Cancer Should be Reconsidered According to Weighting of the T Stage Verification Based on a 25-Year Follow-Up

The gradient monotonicity of existing tumor, node, metastases staging systems for colorectal cancer is unsatisfactory. Our proposed T-plus staging system strengthens weighting of the T stage. In this study, applicability of the T-plus staging system was verified with data of a Chinese colorectal cancer center. Records of 2080 nonmetastatic, advanced cancer patients undergoing colorectal cancer surgery from 1985 to 2011 were reviewed for T, N stage pathology and follow-up information. Using overall and disease-specific survival data, the 7th edition tumor, node, metastases staging system and the T-plus staging system were compared for stage homogeneity and discrimination and gradient monotonicity. For gradient monotonicity, the T-plus staging system was superior for both colon and rectal cancer. With Kaplan-Meier survival curves, the T-plus staging system discriminated among different stages, and the corresponding survival was inversely associated with the stage. However, for the 7th edition tumor, node, metastases staging system, stage IIIa had a better prognosis than stage II for rectal cancer and stage I for colon cancer. For homogeneity within the same stage and discrimination between different stages, the 2 staging systems were similar for colorectal cancer, but the T-plus system was clearly better for colon cancer. The T-plus staging system provides good gradient monotonicity. For future colorectal cancer staging systems, we propose replacement of lymph node status as the criterion to discriminate colorectal cancer stage II and stage III with greater weighting of the T stage.