Validation of the seventh edition of the American Joint Committee on Cancer tumor-node-metastasis (AJCC TNM) staging in patients with stage II and stage III colorectal carcinoma: analysis of 2511 cases from a medical centre in Korea

Aim The sixth and seventh editions of the American Joint Committee on Cancer (AJCC) tumor-node-metastasis (TNM) system for patients with stage II and stage III colorectal carcinoma (AJCC-6 and AJCC-7) were compared. Method Between 2000 and 2007, 2511 stage II/III colorectal carcinoma patients received primary surgical resection at the Asan Medical Center (Seoul, Korea). All patients were staged using AJCC-6 and AJCC-7 TNM systems. Patients with synchronous or other cancers, those given preoperative chemotherapy or radiotherapy and those in whom fewer than 12 lymph nodes were resected, were excluded. Overall survival (OS) and disease-free survival (DFS) were compared. Results Of 2511 patients, 255 (10.2%) had different stages in the AJCC-6 and AJCC-7. For the AJCC-7, the 5-year OS by stage was 94.2% for stage IIA, 88.8% for stage IIB, 83.5% for stage IIC, 91.8% for stage IIIA, 81.8% for stage IIIB and 72.0% for stage IIIC. The OS and the DFS were not significantly different for the new substages IIB (n = 57) and IIC (n = 34) (P = 0.34 and P = 0.87, respectively). For the 187 patients with stage T3N2a cancer, the OS and the DFS were significantly different from stage IIIB other than T3N2a (P = 0.008 and P = 0.01, respectively) and there were no statistically significant differences in OS between the T3N2a group and the IIIC group (P = 0.46). Conclusion The study indicates that AJCC-7 has better prognostic validity than AJCC-6 for staging of patients with stage II and stage III colorectal carcinoma.