Prognostic Significance of Perinephric Fat Infiltration and Tumor Size in Renal Cell Carcinoma

PurposesIt is controversial that perinephric fat infiltration has an impact on survival in patients with renal cell carcinoma. Therefore, we evaluated the influence of perinephric fat infiltration and tumor size on patient survival.Materials and MethodsWe retrospectively reviewed the medical records of 783 and 77 patients with pT1-2 (cN0M0) and pT3a (cN0M0) renal cell carcinoma, respectively. Sporadic unilocular noncystic renal cell carcinoma was included. Univariate and multivariate analyses of prognostic factors, including perinephric fat infiltration, on cancer specific and disease-free survival were performed. Median followup was 56.0 months after surgery.ResultsPatients with pT1-2 and pT3a tumors had a 5-year cancer specific survival rate of 96.1% and 84.9%, and a 5-year disease-free survival rate of 93.4% and 74.7%, respectively (each p <0.01). Age, tumor size and Fuhrman nuclear grade were independent prognostic factors for cancer specific and disease-free survival, whereas perinephric fat infiltration was significant only for disease-free survival. However, perinephric fat infiltration had a significant effect on cancer specific survival in patients with pT3a tumors more than 7 cm (p = 0.001). In contrast, patients with pT3a tumors 7 cm or less had cancer specific and disease-free survival similar to that of patients with pT2 tumors. Recurrence of pT3a tumors greater than 7 cm was observed in 44% of patients but in only 14.6% of those with pT3a tumors 7 cm or less (p = 0.029). In contrast to the recurrence of tumors 7 cm or less, recurrence of pT3a tumors more than 7 cm usually developed at multiple sites with a large tumor burden and it progressed rapidly. Consequently 85% of patients with recurrence of pT3a tumors larger than 7 cm died of renal cell carcinoma compared with 33% of those with recurrence of pT3a tumors 7 cm or less (p = 0.001).ConclusionsIn pT3a renal cell carcinoma tumor size was the strongest prognostic factor of disease-free and cancer specific survival. Perinephric fat infiltration was an independent prognostic factor for disease-free survival but not for cancer specific survival due to the less aggressive behavior of small (7 cm or less) pT3a tumors after recurrence. Tumor size and perinephric fat infiltration should be included in T3a renal cell carcinoma staging.