Objective: To determine the effect of positive surgical margins (PSMs) on oncologic outcomes following robot-assisted partial nephrectomy (RAPN) and to identify factors that increase the likelihood of adverse oncologic outcomes. Methods: A multi-institutional database of patients who underwent RAPN with complete follow-up data was used to compare recurrence-free survival (RFS) and overall survival (OS) between 42 (5.1%) patients with a PSM and 797 (94.9%) patients with a negative surgical margin. Analysis was performed with univariable and multivariable Cox proportional hazard regression models adjusting for confounding variables. A Kaplan-Meier method was used to evaluate the relationship between PSM and oncologic outcomes (RFS and OS), and the equality of the curves was assessed using a log-rank test. Results: The rate of PSM was 5.1%. RFS at 12, 24, and 36 months was 97.8%, 95.2%, and 92.9%. OS at 12, 24, and 36 months was 98.6%, 97.7%, and 93.3%. PSM was not associated with worse RFS in both univariable and multivariable analyses (hazard ratio [HR] = 1.43; 95% confidence interval [CI] = 0.37, 5.55; p = 0.607). Factors associated with worse RFS include pT3a upstaging (HR = 4.97; 95% CI = 1.63, 15.12; p = 0.005), a higher Charlson comorbidity index (HR = 1.68; 95% CI = 1.20, 2.34; p = 0.002); and advanced clinical stage (cT1a vs cT1b, HR = 4.22; 95% CI = 1.84, 9.68; p = 0.001 vs cT2a, HR = 14.09; 95% CI = 3.85, 51.53; p < 0.001). PSM was not associated with worse OS in both univariable and multivariable analyses (HR = 0.87; 95% CI = 0.26, 2.94; p = 0.821). Higher R.E.N.A.L. nephrometry score was found to be associated with worse OS (HR = 1.26; 95% CI = 1.01, 1.57; p = 0.041). Conclusions: Given the absence of association between PSM and worse oncologic outcomes, patients with PSM following RAPN should be carefully monitored for recurrence rather than undergo immediate secondary intervention. As advanced clinical stage (cT1b, cT2a) and pathologic upstaging (pT3a) were independently associated with disease recurrence, their presence may warrant more attentive postoperative surveillance.
Keywords: oncologic outcomes; positive surgical margins; renal-cell carcinoma; robot-assisted partial nephrectomy.