Evaluation of the seventh edition of the tumour, node, metastasis (TNM) classification for colon cancer in two nationwide registries of the United States and Japan.

Abstract

The new TNM classification is currently being implemented. We evaluated the TNM-7 staging system based on the two nationwide colon cancer registries in the United States and Japan to clarify whether this system better stratifies patients' prognoses than the TNM-6 did and to determine whether stratification can be effectively simplified. The Surveillance, Epidemiology, and End Results population-based data from 1988 to 2001 for 50139 colon cancer patients and the multi-institutional registry data from the Japanese Society for Cancer of the Colon and Rectum from 1984 to 1994 for 10754 patients were analysed. We devised a modified version of the TNM-7 staging system to allow simpler classification of the TN categories and compared the TNM-6, TNM-7, modified TNM-7, and the Dukes staging system based on survival curves and objective statistical tests such as likelihood ratio χ(2) tests, Akaike's information criterion, and Harrell's c-index. The TNM-7 was superior to the TNM-6 in all objective statistical tests in the United States (c-index; 0.700 vs 0.696, P<0.001) as well as in the Japan data sets (0.732 vs 0.729, P=0.035). The modified TNM-7 is much simpler, but it nevertheless showed similar values to those of the original TNM-7 (c-index; the United States 0.702, Japan 0.733).   The new TNM-7 is complicated but better at stratifying patients than the TNM-6 in the United States and Japan, and could be effectively simplified.