Validation of the seventh edition of the American Joint Committee on cancer tumor node-staging system in patients with colorectal carcinoma in comparison with sixth classification

Background The aim of this study was to compare survival rates assessed by the seventh-staging system with those by the sixth classification. Methods This was a retrospective study of 3,377 patients who underwent surgery for colorectal adenocarcinoma from three university hospitals. The overall survival (OS) and cancer-specific survival (CSS) rates were compared between patients whose stages according to the seventh-staging system remained the same and patients whose stages migrated, and between subgroups within each new stage (homogeneity analysis). Results In seventh edition, the 5-year OS and CSS rates of patients with T3n2 tumor were significantly greater in the downstaged patients (T3N2a) than in other patients (T3N2b) (OS, P = 0.010; CSS, P = 0.009). The 5-year survival rates for patients with T4a and T4b sub-classifications according to the seventh edition did not differ from those in patients with T4N0-1. Homogeneity analysis of subgroups classified using the new system showed that some subgroups of stage IIIB (T3N2a/T4aN1) had poorer survival rates compared with patients in other sub-categories in the same stage IIIB (P < 0.001). Conclusion Overall, the seventh edition provides a more detailed classification of the prognosis than the old system. However, further study would be warranted to evaluate the validity of sub-classification in seventh TNM-staging system, especially for T4a-b and T3N2a tumors.