Does stage T3a renal cell carcinoma embrace a homogeneous group of patients?

Purpose: Renal cell carcinoma invading the perinephric fat is classified as a stage T3a tumor in the 2002 TNM version. Based on long-term followup we examined the prognostic significance of this definition. Materials and Methods: We evaluated the outcome in 237 consecutive patients with localized renal cell carcinoma operated on between January 1985 and December 1997. Median followup was 8 years. Disease-free survival was analyzed using univariate and multivariate analyses. Based on this we proposed and tested a new TNM system against the 2002 TNM version. Results: Tumor recurrence was diagnosed in 48 patients (20.2%) at a median of 21.5 months. Diameter based analysis of stage T3a revealed that this was an inhomogeneous group that included patients with small tumors and an excellent prognosis along with patients with large tumors and a poor prognosis. Based on this information we initiated a modified TNM staging system that ignores perinephric fat invasion. In the proposed staging system stage T1a includes tumors 4 cm or less and stage T1b includes tumors more than 4 but 7 cm or less. Stage T2 is divided into T2a-tumors greater than 7 but 10 cm or less and T2b-tumors greater than 10 cm. Stage T3a is reserved for renal vein tumor invasion. The proposed TNM performed better than the 2002 version using the Nagelkerke R-2 test (0.439 vs 0.359), and the Hosmer and Lemeshow test (0.335 vs 0.191). Conclusions: The current definition of stage T3a renal cell carcinoma embraces an inhomogeneous group of patients with marked differences in prognosis. We believe that tumor invasion into the perinephric fat does not necessarily predict aggressive biological behavior.