Objectives: To compare the prognostic value of the sixth and seventh editions of the TNM classification, and of additional prognostic factors, in colorectal cancer.
Background: The seventh TNM edition was released in 2009 with the aim of providing a more precise prediction of prognosis.
Methods: Clinical and histopathological data of 2229 patients with colorectal cancer who underwent tumor resection between 1990 and 2006 were analyzed and compared by using the sixth and seventh editions of the TNM classification and a statistically calculated model of prognostic factors.
Results: With the sixth edition, 5-year survival was 96% for stage I, 90% for IIA, 86% for IIB, 90% for IIIA, 72% for IIIB, 48% for IIIC, and 13% for IV. With the seventh edition, 5-year survival was 96% for stage I, 90% for IIA, 84% for IIB, 87% for IIC, 89% for IIIA, 72% for IIIB, 36% for IIIC, 15% for IVA, and 10% for IVB. The stage shifted for only 155 (7%) patients: from IIB to IIC (2%), from IIIB to IIIC (1%), and from IIIC to IIIA/B (4%). The performance of the seventh edition [concordance index (c-index) 0.83; 95% confidence interval (CI), 0.82-0.85] revealed no relevant improvement compared with the sixth edition (c-index 0.83; 95% CI, 0.82-0.84), or compared to a model based on independent prognostic factors (c-index 0.84; 95% CI, 0.83-0.86).
Conclusions: The seventh TNM edition did not provide greater accuracy in predicting colorectal cancer patients' prognosis but resulted in a more complex classification for daily clinical use.