Cold Versus Warm Ischemia Robot-Assisted Partial Nephrectomy: Comparison of Functional Outcomes in Propensity-Score Matched "At Risk" Patients

Objectives: To compare functional outcomes of warm ischemia RPN (wRPN) to cold ischemia RPN (cRPN) in at risk patients. Materials and Methods: Retrospective review of institutional database queried for all patients who underwent cRPN/wRPN (January 2007-December 2016). For the study purpose, patients with solitary kidney and/or history of partial nephrectomy and/or multiple tumors and/or preoperative estimated Glomerular Filtration Rate (eGFR) <60mL/minute were extracted. To reduce inherent biases, groups were matched on key variables related to renal function through a greedy matching algorithm with no replacement. Renal functional outcomes were evaluated by eGFR drops at 1-3 days and at 1, 3, 6, and 12 months postoperatively. A linear mixed effects model was used to assess eGFR at each follow-up who received either cRPN or wRPN. Follow-up was treated as a factor variable to account for nonlinear time trends. Contrast analysis was used to compare cRPN vs wRPN groups at each follow-up, using Sidak-Holm p-value adjustments for multiple comparisons. Results: Out of 19 cRPN patients and 279 wRPN patients, 14 cRPN patients were finally matched 1:1 with no replacement to 14 wRPN. There was no significant difference in preoperative eGFR for matched patients undergoing cRPN vs wRPN. Since the first postoperative day, cRPN patients had higher eGFR. The difference was statistically significant since the third month postoperatively (mean difference=18.201, 95% confidence interval [CI]: 1.930-34.472) and remained at both the sixth month (mean difference=18.839, 95% CI: 2.568-35.109) and the 12th month (mean difference=21.277, 95% CI: 5.006-37.547) follow-up. Conclusions: Accounting for unmodifiable and modifiable factors, in a cohort of highly selected patients at risk for postoperative significant decline in renal function after RPN, renal functional outcomes appear to be superior with cold ischemia technique.