Assessing the Trade-off Between the Safety and Effectiveness of Off-clamp Robotic Partial Nephrectomy for Renal Masses with a High RENAL Score: A Propensity Score-matched Comparison of Perioperative and Functional Outcomes in a Multicenter Analysis

Background: Tumors with a high nephrometry score represent a challenging surgical scenario for which robotic partial nephrectomy (RPN) is a primary option in expert hands. Objective: To compare perioperative and functional outcomes of off-clamp and on-clamp RPN in patients with renal masses with a high RENAL score (≥9). Design, setting, and participants: For this retrospective analysis, an RPN data set including 1604 patients treated at three institutions between 2003 and 2021 was queried for cases with a RENAL score ≥9. Outcome measurements and statistical analysis: We used 1:1 propensity score matching (PSM) to select a cohort in which imbalances between the off-clamp and on-clamp groups were minimized. We used χ2 and Student t tests to compare categorical and continuous variables, respectively. The Kaplan-Meier method was used to compare the probability of having an estimated glomerular filtration rate (eGFR) ≥45 ml/min during follow-up. Univariable and multivariable analyses were performed to identify predictors of a trifecta outcome (negative surgical margin status, no Clavien-Dindo grade ≥3 complications, eGFR decline ≤30%) and of retaining eGFR ≥45 ml/min over time. Results and limitations: From an overall cohort of 354 patients (142 on-clamp, 212 off-clamp), a homogeneous PSM cohort of 78 patients in each group was selected (p ≥ 0.17). In the PSM cohort, operative time was significantly shorter in the off-clamp group (p < 0.001). There were no differences between the groups in the rates of severe complications (p = 0.32) and positive surgical margins (p = 0.24). The rate of trifecta achievement was significantly higher in the off-clamp group (83.3% vs 67.9%; p = 0.03). Warm ischemia time >20 min was independently negatively associated with trifecta achievement (odds ratio 0.32, 95% confidence interval 0.14-0.74). Moreover, the off-clamp group had a significantly higher probability of retaining eGFR ≥45 ml/min over time (3 yr: 95.9% vs 81.6%; p = 0.03); every 1-min increase in warm ischemia time reduced this probability by 1.3%. Conclusions: We found a favorable trade-off between the benefits and risks of off-clamp RPN, with similar perioperative outcomes and a net benefit in terms of trifecta achievement and long-term renal function outcomes in comparison to on-clamp RPN. Patient summary: The complexity of surgery for kidney tumors can be assessed using the RENAL score, which is a measure of the location and size of a kidney tumor. In a multicenter series of patients with tumors with a high RENAL score, we compared outcomes between strategies with (on-clamp) and without (off-clamp) clamping of kidney blood vessels during robot-assisted removal of part of the affected kidney. We found that off-clamp surgery results in better postoperative kidney function.