Introduction: The advantages of off-clamp (off) vs on-clamp (on) robot-assisted partial nephrectomy (RAPN) is debatable due to conflicting results in terms of perioperative and functional outcomes. However, warm ischemia time (WIT) for low complexity renal masses is likely to be < 25 minutes. Here, hypothetical benefit of off-RAPN might be diluted. Conversely, for complex renal masses, when prolonged WIT may be anticipated, off-RAPN approach may prove its advantage. We hypothesized that on-RAPN exhibited worse perioperative and functional outcomes relative to off-RAPN especially for more complex renal cases. Methods: Whitin a multi-institutional database we indentified patients with kidney tumors (cT1-2, cN0, cM0) treated with on-RAPN vs off-RAPN. Exclusion criteria were multiple lesions, solitary kidney, selective clamping. To maximally reduce covariates imbalance, 1:1 propensity score matching (PSM) between on- vs off-RAPN was performed adjusting for important confounders (age, sex, ASA, baseline eGFR, Hypertension, Diabetes, BMI, RENAL). After PSM, logistic regression models addressed trifecta achievement and Cox regression models addressed any upstaging to CKD = 3a (CKD-upstaging) for on- vs off-RAPN. Trifecta was defined as combination of negative surgical margins, no perioperative Clavien=3 complications and absence of significant perioperative eGFR decline (>30%). All analysis were repeated after stratification according to RENAL score <7 vs =7. Results: Overall, 1015 patients were identified between on- vs off-RAPN (37.0 vs 63.0%). After PSM, on-RAPN yielded a higher risk of CKD-upstaging (HR 1.39, 95%CI: 1.00-1.93; p=0.047). Moreover, on-RAPN reduce the probability of achieving trifecta (OR 0.37, 95%CI: 0.25- 0.56; p<0.001). In subgroup analysis, on-RAPN yielded a higher risk of CKD-upstaging in more complex (HR 1.83, 95%CI 1.15-2.90, p=0.011), but not les complex cases (HR 1.31, 95% CI: 0.79-2.17; p=0.3). Simirarly, on-RAPN strongly reduce the probability of achieving trifecta in more complex (OR 0.26, 95%CI 0.15-0.44, p<0.001), but not in less complex less cases (OR 0.56, 95% CI: 0.29-1.06; p=0.079). Conclusions: In the current study, on-RAPN was associated with worse perioperative and functional outcomes relative to their counterparts in the overall cohort, as well as in more complex, but not in less complex renal masses. In conclusion, a greater detrimental effect of on-RAPN was detected for complex renal masses, for whom a prolonged WIT is required. SOURCE OF Funding: no
