Association between renal mass biopsy and upstaging to perinephric fat involvement in a contemporary cohort of patients with clinical T1a renal cell carcinoma

Although tumor tract seeding from renal mass biopsy (RMB) is exceedingly rare, the possibility of tumor capsule violation from RMB leading to perinephric fat invasion has not been quantified. We evaluated the association between RMB and perinephric fat invasion in patients with clinical T1a renal cell carcinoma who underwent partial or radical nephrectomy.We reviewed the National Cancer Database from 2010-2013 and identified patients who underwent surgery for clinical T1a tumors. Patients were classified as upstaged only if final pathology demonstrated perinephric invasion only (pT3a). Mixed-effect logistic regression analysis was performed on inverse probability weighted matched groups to identify predictors of perinephric fat invasion. Multivariable Cox proportional hazards models and Kaplan-Meier survival curves were used to evaluate overall survival (OS).A total of 24,548 patients met our inclusion criteria. Pathologic upstaging to pT3a perinephric fat involvement occurred in 1.2% of patients. This rate of upstaging was 1.1% in the no biopsy group compared with 2.1% in patients who underwent RMB (P0.01). In multivariable logistic model, RMB was associated with pT3a perinephric fat upstaging (OR 1.69, 95% CI 1.17-2.44, P0.01). Upstaging to pT3a was also associated with worse OS (HR 1.71, 95% CI 1.13-2.60, P = 0.01). Kaplan-Meier survival curves demonstrated similar OS estimates in patients upstaged to pT3a disease, irrespective of undergoing RMB or not (Log-Rank = 0.87).RMB was associated with increased rate of upstaging to pT3a perinephric fat involvement in clinical T1a RCC. This effect is small with unclear clinical significance. This is perhaps balanced by the importance of the information acquired from biopsies. Future studies are needed to elucidate clinical significance of this finding.