Analysis of the seventh edition of American Joint Committee on colon cancer staging.

Purpose: The seventh edition of the American Joint Committee on Cancer (AJCC) staging system has new substages for colon cancer. We used survival data from a single medical center to analyze this new AJCC edition.
Methods: The colon cancer database of Taipei Veterans General Hospital provided 1,865 patient records covering from 1999 to 2005. Survival rates were evaluated using the Kaplan-Meier method.
Results: There were 268, 607, 561, and 421 patients in stages I, II, III, and IV disease with 5-year observed survival rates of 86.3%, 79.2%, 65.4%, and 12.8%, respectively. Survival rates were not significantly different between those with T4a and T4b disease (P = 0.806). The outcome of N1c disease was similar to N1a and N1b but worse than N0 (P = 0.004). Survival rates for M1a and M1b disease became different after reclassifying solely peritoneal seeding as M1a (P < 0.001). No discrepancy of outcomes between stage IIIA and stage IIB/IIC remained in the seventh edition.
Conclusions: Evolution from the fifth to seventh edition of the AJCC staging system is successful in separating prognostic groups by substaging. But some issues remain unresolved, including the subdivision of T4, N1, and M1.