Off-clamp vs on-clamp robotic partial nephrectomy: perioperative, functional and oncological outcomes from a propensity-score matching between two high-volume centers

Introduction: Aim of the study was to compare perioperative, functional and oncological outcomes after off-clamp vs on-clamp robotic partial nephrectomy (RPN). Materials and methods: Patients who underwent off-clamp or on-clamp (warm ischemia) RPN were extracted from 2 institutional prospectively-maintained databases. 123 patients who underwent off-clamp RPN at one institution were excluded, so that each institution contributed with unselected patients (institution 1:on-clamp RPN vs institution 2:off-clamp). 2:1 propensity-score matching (age, sex, smoking, diabetes, hypertension, ASA score, solitary kidney, preoperative eGFR, tumor size and R.E.N.A.L.score). Perioperative outcomes were compared. A linear mixed model was fitted to eGFR as the outcome regressed on fixed effects for 1) management of clamping (on-clamp/off-clamp), 2) time (at baseline, at discharge, at 12 and 24 months postoperatively), and 3) clamp/time interaction. Survival events were compared between groups. Results: 1983 patients were pooled. After matching, 400 on-clamp vs 200 off-clamp patients were analyzed. No significant differences were found in key perioperative outcomes. The effect of on-clamp on eGFR changed over time. At discharge, groups had similar drop in eGFR. The difference between groups was greatest at 12-months postoperatively, with on-clamp patients showing a deficit of 5 ml/min. At 24-months follow-up, this gap shrunk to 2 ml/min. There were no significant differences in overall survival (p = 0.1), recurrence (χ2 = 0.008, p = 0.9), or metastasis free survival (χ2 = 0.962 p = 0.3). Only one cancer-specific death occurred in off-clamp group. Conclusion: We confirm no significant differences in the perioperative and oncological outcomes between off-clamp and on-clamp RPN. Avoided ischemia benefits renal function within 1-year follow-up after surgery. At longer follow-up, difference with on-clamp is softened.