Impact and prognostic implications of colon cancers stage II sub-classification through the years.

Purpose: According to the American Joint Committee on Cancer (AJCC) 7th edition, T4 colon cancers have been sub-divided into T4a and T4b, resulting in a stage II sub-classification (T3N0, T4aN0, and T4bN0). This study was aimed: (a) to investigate the impact of the AJCC 7th edition stage II sub-classification on the overall survival (OS), disease-free survival (DFS) and disease-specific survival (DSS) of colon cancer patients who underwent surgical resection and (b) to compare the last three AJCC editions for identifying stage II patients with high-risk of progression.
Methods: One hundred seventy-eight stage II colon cancers out of 682 colorectal cancer patients who underwent surgical resection were selected. T4N0 were sub-divided in accordance with the AJCC 7th edition. Mean follow-up was 41.9 months. Kaplan-Meier method was employed to estimate the survival curves.
Results: OS analysis documented a significant difference between stage-sub-groups using the 6th edition; conversely, this difference was not seen if the 7th edition was applied (p = 0.03 and 0.12, respectively). Stage II DFS analysis reported a significant difference using both the AJCC 6th and 7th editions (p = 0.03 and 0.02, respectively). A significant difference was reported on stage II DSS analysis using the AJCC 6th edition (p = 0.03); however, when the 7th edition was applied, a substantial discrepancy between survival curves was noted with T3N0 and T4aN0 displaying similar outcomes (p = 0.006).
Conclusions: The AJCC 7th edition is a reliable classification that might implement the identification of those stage II colon cancer patients with high-risk of progression, recurrence, and cancer mortality.