Validation of the 2009 TNM Classification for Renal Cell Carcinoma: Comparison with the 2002 TNM Classification by Concordance Index

ABSTRACT

PURPOSE: To assess the validity of the 2009 TNM classification for renal cell carcinoma (RCC) and compare its ability to predict survival relative to the 2002 classification. MATERIALS AND METHODS: We identified 1,691 patients who underwent radical nephrectomy or partial nephrectomy for unilateral, sporadic RCC between 1989 and 2007. Cancer-specific survival was estimated by the Kaplan-Meier method and was compared among groups by the log-rank test. Associations of the 2002 and 2009 TNM classifications with death from RCC were evaluated by Cox proportional hazards regression models. The predictive abilities of the two classifications were compared by using Harrell's concordance (c) index. RESULTS: There were 234 deaths from RCC a mean of 38 months after nephrectomy. According to the 2002 primary tumor classification, 5-year cancer-specific survival was 97.6% in T1a, 92.0% in T1b, 83.3% in T2, 61.9% in T3a, 51.1% in T3b, 40.0% in T3c, and 33.6% in T4 (p for trend<0.001). According to the 2009 classification, 5-year cancer-specific survival was 83.2% in T2a, 83.8% in T2b, 62.6% in T3a, 41.1% in T3b, 50.0% in T3c, and 26.1% in T4 (p for trend<0.001). The c index for the 2002 primary tumor classification was 0.810 in the univariate analysis and increased to 0.906 in the multivariate analysis. The c index for the 2009 primary tumor classification was 0.808 in the univariate analysis and increased to 0.904 in the multivariate analysis. CONCLUSIONS: Our data suggest that the predictive ability the 2009 TNM classification is not superior to that of the 2002 classification.