Pathologic staging of renal cell carcinoma: significance of tumor classification with the 1997 TNM staging system.

Background: The TNM staging system for renal cell carcinoma was revised by the American Joint Committee on Cancer (AJCC) and the International Union Against Cancer (UICC) in 1997. The 1997 TNM staging system for renal cell carcinoma reclassifies tumors using criteria for size and for extent of renal vein/vena cava involvement that are different from the criteria used in the 1987 staging system. The current study investigated the prognostic significance of tumor classification and other factors using the new staging system.

Methods: Records from 1547 renal cell carcinoma patients (1039 males and 508 females; mean age, 63.4 years; mean follow-up, 7.1 years) who underwent surgical resection between 1970 and 1998 were analyzed retrospectively. Tumors were staged using the 1987 and 1997 TNM criteria, and Kaplan-Meier estimates of survival and disease recurrence were compared for both staging systems. The Peto-Peto log rank test and the generalized Wilcoxon test were used to assess univariate significance of prognostic factors on survival. Cox proportional hazards regression analysis was then completed to assess the significance of the revised staging system.

Results: Tumor classification using the 1987 TNM staging system (P = 0.0001) and the 1997 TNM staging system (P = 0.0001) was a significant predictor of cause specific survival. Using 1997 TNM staging criteria, 641 patients were reclassified from the T2 classification to the T1 classification, 114 patients were reclassified from the T3c classification to the T3b classification, 11 patients were reclassified from the T4b classification to the T3c classification, and 3 patients were reclassified from the T4b classification to the T3b classification. Patients with reclassified tumors had outcomes similar to patients with tumors that remained in the same tumor classification. Patient stratification was improved using the new staging system. Prognostic discrimination for cause specific survival at 10 years was noted for the 1987 and 1997 TNM classifications (T1, 97% vs. 91%; T2, 84% vs. 70%; T3a, 53% vs. 53%; T3b, 48% vs. 42%; and T3c, 29% vs. 43%).

Conclusions: The revised classification of renal cell carcinoma was a significant predictor of cause specific survival for the cohort of patients described in this report. Using the new system, the stratification of patients was improved. Patients who had their tumors reclassified as a result of the new staging system had outcomes similar to those of patients who had tumors that remained in the same classification. Based on an analysis of this cohort, tumor classification is valid, and the T1 subclassification is warranted. However, additional revision may be required to optimize staging.