Although partial nephrectomy has become the gold standard for T1 renal tumors whenever technically feasible, simple enucleation has shown superior results. To the best of our knowledge, no randomized controlled trials comparing these two surgical approaches have been published.
To compare the surgical margin status for robot-assisted simple enucleation (RASE) and standard robot-assisted partial nephrectomy (sRAPN) for clinical T1 renal tumors.
This is a prospective, randomized, controlled, noninferiority trial. A total of 380 patients aged 18-80 yr with newly diagnosed, sporadic, unilateral clinical T1 renal tumors (RENAL score <10) were enrolled and randomized to RASE or sRAPN. The primary endpoint was the positive surgical margin (PSM) rate, with a noninferiority margin of 7.5% set. The study was registered on ClinicalTrials.gov (NCT03624673).
We defined noninferiority for RASE versus standard RAPN as an upper 95% confidence interval (CI) bound of <7.5% for the difference in the proportion of patients with a PSM.
A cohort of 380 patients was enrolled and randomly assigned to RASE (n = 190) or sRAPN (n = 190). On intention-to-treat analysis for patients with malignant tumors, 2.3% of patients in the RASE group and 3.0% in the sRAPN group had a PSM. The RASE group showed noninferiority to the sRAPN group within a 7.5% margin (difference -0.7%, 95% CI -4.0% to 2.7%). Per-protocol analysis also demonstrated noninferiority of RASE. The RASE group had a shorter median operative time (145 vs 155 min; p = 0.018) and a lower rate of tumor bed suturing (8.9% vs 43%; p  0.9).
RASE for the management of low- to intermediate-complexity tumors is noninferior to sRAPN in terms of the PSM rate. Long-term follow-up is needed to draw conclusions regarding oncological outcomes.
We carried out a trial to compare simple tumor enucleation versus partial nephrectomy for renal tumors. The outcome we assessed was the proportion of patients with a positive surgical margin. Our results show that simple tumor enucleation is not inferior to partial nephrectomy for this outcome. Longer follow-up is needed to assess other cancer control outcomes.

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