Prognostic significance of the 1997 TNM classification of renal cell carcinoma

The TNM classification of renal cell carcinoma was recently revised in 1997. The most significant change from the previous edition (1987) is an increase in the size cutoff between T1 and T2 tumors from 2.5 to 7.0 cm. We compared the 1997 and 1987 TNM staging classifications in predicting patient outcome.

A total of 381 patients who underwent nephrectomy for renal cell carcinoma at our hospital between 1968 and 1994 were identified. Mean patient age was 61 years (range 15 to 89) and mean followup was 64.5 months. All pathological slides were re-reviewed in uniform manner and staged using the 1987 and 1997 TNM classifications. The impact of numerous pathological factors and each staging classification on disease specific survival and freedom from progression were statistically analyzed, and Kaplan-Meier survival curves were generated and compared.

The 1997 TNM classification resulted in a redistribution of 170 cases previously classified as stage II (T2N0M0) to stage I (T1N0M0) under the new system. Both classifications were strong predictors of survival on univariate and multivariate analyses, and essentially equivalent in the ability to predict patient outcome. However, comparison of survival curves on Kaplan-Meier life tables revealed better separation of survival for stage I (T1N0M0) and stage II (T2N0M0) cases under the 1997 TNM classification, with survival for TNM stage I essentially remaining unchanged.

The 1997 TNM classification of renal cell carcinoma appears to be equivalent to the previous classification in predicting outcome but permits better stratification of cases according to survival and, therefore, may have improved clinical usefulness.