Purpose: As a result of the observation that the potential biological aggressiveness of even early stage renal cell cancer (RCC) strongly correlates with tumor size, the 5th edition of the TNM system (1997), which classifies all renal tumors up to a maximum diameter of 7 cm as T1, was modified in the current classification to distinguish T1a and T1b tumors based on a cut-off of 4 cm. Only a few larger investigations supporting this cut-off are available in the literature and these are based on univariate statistical analysis. To determine whether this cut-off best reflects the correlation between aggressive potential and tumor size and thus differentiates patients at low or high risk of progression, this investigation was performed using both univariate and multivariate statistical analysis.
Materials and methods: Between 1981 and 2000, a total of 652 patients underwent tumor nephrectomy for renal cell carcinoma. Of these, the 243 patients with local RCC not extending beyond the renal capsule were subjected to univariate (log rank test) and multivariate (Cox regression model) statistical analysis.
Results: It became evident that, while during univariate analysis the prognostic calue of a cut-off size of 4 cm was confirmed, multivariate analysis identified the highest relative risk of cause-specific death (2.93) in those patients with tumors larger than 5 cm maximum diameter.
Conclusions: The 5 cm cut-off thus appears to best determine the clinical prognosis for patients undergoing tumor nephrectomy for early stage renal call cancer. Taking this into consideration, the present study clearly demonstrates the reed for a multivariate statistical approach when the current modification of the TNM classification system is critically reevaluated.