Greater Renal Function Benefit from Enucleation Technique for More Complex Renal Tumors in Robot-Assisted Partial Nephrectomy.

Background: Tumor enucleation technique in robot-assisted partial nephrectomy (RAPN) reportedly contributes to renal function preservation. Which tumors and which part to utilize this technique have not been determined. Patients and Methods: This multi-institutional retrospective study included patients who underwent RAPN at tertiary surgery centers. Patients were first stratified into High, Intermediate, and Low categories based on renal nephrometry score. Patients were further classified into I/B-enucleation (I/B-E, I + B ≤ 1) and I/B-resection (I/B-R, I + B ≥ 2) groups based on surface-intermediate-base margin score. Perioperative outcomes, including percentile change in estimated glomerular filtration rate (eGFR), new-onset chronic kidney disease, complication rate, surgical margin, and trifecta achievement, were compared between the I/B-E and I/B-R groups in each category. Odds ratios (ORs) and β-coefficients were also compared. Results: Overall, 704 patients were included in this study. Relative decrease in eGFR was significantly lower for the I/B-E group in all three categories, with medians of 8.1%, 4.4%, and 3.2% in the High, Intermediate, and Low, respectively. In multivariate analyses, excision technique was independently associated with eGFR change in all three. β-coefficient was higher in the High (5.06) category than in the Low (3.17) or Intermediate (3.33). Across all three categories, significantly more patients attained trifecta with a difference of 34.0%, 18.3%, and 15.1% in the High, Intermediate, and Low categories, respectively (all, p < 0.05), with a higher OR in the High (5.91) category than in the Low (3.20) or Intermediate (2.48). No significant differences were found in operation time, amount of estimated blood loss, rate of positive surgical margin, or complications. Warm ischemic time was significantly longer for the I/B-E group in the Intermediate (18.0 minutes vs 16.0 minutes, p = 0.002) and Low categories (13.0 vs 11.0, p = 0.006), but not significant in High (p = 0.344). Conclusions: I/B-enucleation in RAPN contributes to renal function preservation, and the impact was more emphasized in complex tumors.