Incidence of T3a upstaging and survival after partial nephrectomy: Size-stratified rates and implications for prognosis.

Abstract

4588 Background: The use of partial nephrectomy (PN) to treat renal cell carcinoma has grown in the past decade, with expansion to larger tumors. Performing PN for larger tumors may increase the number of patients up-staged to pT3a after surgery, who may have underwent radical nephrectomy (RN), if known preoperatively. We aimed to estimate the proportion of patients up-staged to T3a disease after PN, stratified by size. We also compared size-stratified survival of up-staged pT3a patients to those with T1a, T1b, or T2 disease. Methods: From 1998 – 2013, we identified patients undergoing PN or RN from the Surveillance Epidemiology and End Results registries. The proportion of patients receiving PN found to have pT3a disease was quantified by size. Cox proportional hazards models compared cancer-specific (CSS) and overall survival (OS) for PN patients with pT1a, pT1b, and pT2 disease to size-stratified pT3a patients. Also, we compared PN patients with pT3a disease to RN patients with pT3a disease. Results: From the 28,854 patients undergoing PN, the estimated proportion up-staged to pT3a increased along with tumor size: 4.2% for T1a, 9.5% for T1b, and 19.5% for T2. Among those receiving PN, survival analysis showed worse CSS for up-staged pT3a patients versus stratified pT1a (HR = 1.87, p = 0.02), pT1b (HR = 1.91, p = 0.01), and pT2 (HR = 2.33, p = 0.01) patients. When assessing OS, only in tumors < 4cm did the pT3a cohort demonstrate worse OS (HR = 1.25, p = 0.04). Comparing PN and RN for pT3a disease, size-adjusted analysis revealed no difference in CSS or OS. Lastly, among pT3a patients undergoing PN, patients with larger tumors, measuring 4 – 7cm (OS: HR = 1.44, p = 0.04) or 7 – 16cm (OS: HR = 2.64, p < 0.01), had worse survival than those with tumors < 4cm. Conclusions: A greater proportion of patients experience T3a up-staging after PN with increasing initial T stage. Up-staged pT3a patients have worse CSS after PN compared to those with similarly sized localized tumors. Also, pT3a patients after PN showed similar survival to pT3a patients after RN. However, pT3a patients undergoing PN had worse survival with increasing tumor size, reinforcing the need for improvements in identifying patients at risk of up-staging.