Proposal for revision of the TNM classification system for renal cell carcinoma

Background: The current study defined an optimal tumor size breakpoint to stratify localized renal cell carcinoma (RCC) into groups with significantly different cancer-related outcomes and proposed a revision of the TNM classification system.

Methods: The authors analyzed the data from 1138 patients who had undergone partial or radical nephrectomy for localized RCC at 7 European urologic centers. The optimal pathologic size breakpoint was calculated using the martingale residuals from a Cox proportional hazards regression model.

Results: The mean follow-up time was 87 months. The scatterplot of tumor size versus expected risk of death per patient suggested that an interval of 5-6 cm was appropriate. A total of 720 (63.3%) and 418 (36.7%) patients had tumors measuring < or = 5.5-cm and tumors measuring > 5.5-cm, respectively. Significant cancer-specific survival differences between the two groups of patients were reported in the series by all the centers participating in the study. On univariate analysis, the other variables found to be associated with cancer-specific survival were the patient's age, symptomatic tumor presentation, and the Fuhrman nuclear grade. On multivariate analysis, the pathologic stage of the primary tumor defined according to the 5.5-cm breakpoint was found to be an independent predictor of cancer-specific survival, as well as age, mode of presentation, and nuclear grade. According to the multivariate analysis, the authors clustered patients into 3 groups with statistically significant outcome differences: 1) patients with < or = 5.5-cm incidentally detected RCC; 2) patients with < or = 5.5-cm symptomatic RCC; and 3) patients with > 5.5-cm RCC. This cancer-related outcome stratification was valid regardless of the patient's age.

Conclusions: The 5.5-cm breakpoint was found to be the optimal tumor size breakpoint with which to stratify patients with organ-confined RCC. The study supported the upgrade of the TNM classification system according to this breakpoint.