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

BACKGROUND: The use of partial nephrectomy (PN) to treat renal cell carcinoma has grown to include larger, more complex tumors. Such tumors are more likely to be up-staged to pT3a and generate controversy regarding the oncologic safety of PN. We aimed to estimate the proportion of patients up-staged to T3a disease after PN, stratified by clinical stage, and characterize their survival.
METHODS: From 1998 to 2013, pT1-pT3aN0M0 kidney cancer patients undergoing PN or radical nephrectomy (RN) were identified from the Surveillance Epidemiology and End Results registries. Cox proportional hazards models compared cancer-specific (CSS) and overall survival (OS) for PN patients with pT1a, pT1b, and pT2 disease to stratified, up-staged pT3a patients undergoing PN. Also, we compared PN patients with up-staged pT3a disease to RN patients with pT3a disease.
RESULTS: From the 28,854 patients undergoing PN, the estimated proportion up-staged to pT3a was 4.2%, 9.5%, and 19.5% for cT1a, cT1b, and cT2, respectively. OS was worse for tumors up-staged from cT1a to pT3a, but not for cT1b or cT2 tumors. Up-staged pT3a tumors across all stage strata demonstrated worse CSS, with worse survival for larger tumors. Analysis revealed no difference in OS or CSS for up-staged pT3a PN patients compared to pT3a RN patients.
CONCLUSIONS: A greater proportion of patients experience T3a up-staging after PN with increasing initial T stage. Up-staged pT3a patients have worse CSS across all clinical tumor stages after PN. However, our results do not demonstrate that patients up-staged after PN have compromised oncologic outcomes compared to all-comers with pT3a disease receiving RN.