Efficacy of robot-assisted partial nephrectomy compared to conventional laparoscopic partial nephrectomy for completely endophytic renal tumor: a multicenter, prospective study

Background: This study aimed to compare the efficacy of robot-assisted partial nephrectomy for completely endophytic renal tumors with the reported outcomes of conventional laparoscopic partial nephrectomy and investigate the transition of renal function after robot-assisted partial nephrectomy. Methods: We conducted a prospective, multicenter, single-arm, open-label trial across 17 academic centers in Japan. Patients with endophytic renal tumors classified as cT1, cN0, cM0 were included and underwent robot-assisted partial nephrectomy. We defined two primary outcomes to assess functional and oncological aspects of the procedure, which were represented by the warm ischemic time and positive surgical margin, respectively. Comparisons were made using control values previously reported in laparoscopic partial nephrectomy studies. In the historical control group, the warm ischemia time was 25.2, and the positive surgical margin was 13%. Results: Our per-protocol analysis included 98 participants. The mean warm ischemic time was 20.3 min (99% confidence interval 18.3–22.3; p < 0.0001 vs. 25.2). None of the 98 participants had a positive surgical margin (99% confidence interval 0–5.3%; p < 0.0001 vs. 13.0%). The renal function ratio of eGFR before and after protocol treatment multiplied by splits was 0.70 (95% confidence interval: 0.66–0.75). Factors such as preoperative eGFR, resected weight, and warm ischemic time influenced the functional loss of the partially nephrectomized kidney after robot-assisted partial nephrectomy. Conclusions: Robot-assisted partial nephrectomy for completely endophytic renal tumors offers a shorter warm ischemia time and comparable positive surgical margin rate compared with conventional laparoscopic partial nephrectomy.