Impact of tumor size on the predictive ability of the pT3a primary tumor classification for renal cell carcinoma

PURPOSE: The accuracy of the pT3a primary tumor classification for renal cell carcinoma has been questioned recently. We investigated the association of perinephric and renal sinus fat invasion with death from renal cell carcinoma independent of tumor size. MATERIALS AND METHODS: We identified 2,165 patients treated with open radical nephrectomy or nephron sparing surgery for clinically localized, sporadic pT1a, pT1b, pT2 or pT3a renal cell carcinoma between 1970 and 2002. Patients with pT3a disease were then subdivided into 3 groups according to tumor size to match the size definitions for the pT1a, pT1b and pT2 tumor classifications. RESULTS: There were 834 patients with pT1a RCC, 674 with pT1b, 494 with pT2 and 163 with pT3a RCC. At last followup 317 patients died of RCC at a median of 3.8 years following surgery. The median followup among the 1,087 patients still alive at last followup was 7.8 years (range 0 to 34). The risk ratios (95% CI) for the association between fat invasion and death from RCC among patients with tumors 4 cm or smaller, 4 to 7 cm and more than 7 cm were 6.15 (1.84-20.50, p = 0.003), 4.12 (2.50-6.78, p <0.001) and 2.13 (1.53-2.97, p <0.001), respectively. These associations remained statistically significant in a multivariate analysis that included nuclear grade and histological coagulative tumor necrosis. CONCLUSIONS: Peripheral perinephric and renal sinus fat invasion was associated with death from RCC independent of tumor size. Our data contradict reports suggesting that pT3a tumors should be reclassified according to tumor size only.