Impact of positive surgical margins on survival after partial nephrectomy in localized kidney cancer: analysis of the National Cancer Database.

BACKGROUND The impact of positive surgical margins (PSM) on outcomes in partial nephrectomy (PN) is controversial. We investigated impact of PSM for patients undergoing PN on overall survival (OS) in different stages of renal cell carcinoma (RCC). METHODS Retrospective analysis of patients from the US National Cancer Database who underwent PN for cT1a-cT2b N0M0 RCC between 2004-13. Patients were stratified by pathological stage [pT1a, pT1b, pT2a, pT2b, and pT3a (upstaged)] and analyzed by margin status. Cox Regression multivariable analysis (MVA) was performed to investigate associations of PSM and covariates on all-cause mortality (ACM). Kaplan-Meier analysis (KMA) of OS was performed for PSM versus negative margin (NSM) by pathological stage. Subanalysis of Charlson Comorbidity Index 0 (CCI=0) subgroup was conducted to reduce bias from comorbidities. RESULTS We analyzed 42,113 PN [pT1a 33341 (79.2%) pT1a, pT1b 6689 (15.9%), pT2a 757 (1.8%), pT2b 165 (0.4%) and pT3a upstaged 1161 (2.8%)]. PSM occurred in 6.7% (2823) [pT1a 6.5%, pT1b 6.3%, pT2a 5.9%, pT2b 6.1%, pT3a 14.1% p<0.001]. On MVA, PSM was associated with 31% increase in ACM (HR 1.31, p<0.001), which persisted in CCI=0 subanalysis (HR 1.25, p<0.001). KMA revealed negative impact of PSM vs. NSM on 5-year OS: pT1 (87.3% vs. 90.9%, p<0.001), pT2 (86.7% vs. 82.5%, p=0.48), and upstaged pT3a (69% vs. 84.2%, p<0.001). CONCLUSIONS PSM after PN was independently associated with across-the-board decrement in OS, which worsened in pT3a disease and persisted in subanalysis of patients with CCI=0. PSM should prompt more aggressive surveillance or definitive resection strategies.