The IRON Study: Investigation of Robot-assisted Versus Open Nephron-sparing Surgery

Background: Current literature does not provide large-scale data regarding clinical outcomes of robot-assisted (RAPN) versus open (OPN) partial nephrectomy. Moreover, data assessing predictors of long-term oncologic outcomes after RAPN are scarce. Objective: To compare perioperative, functional, and oncologic outcomes of RAPN versus OPN, and to investigate the predictors of oncologic outcomes after RAPN. Design, setting, and participants: This study included 3467 patients treated with OPN (n = 1063) or RAPN (n = 2404) for a single cT_1–2N₀M₀ renal mass from 2004 to 2018 at nine high-volume European, North American, and Asian institutions. Outcome measurements and statistical analysis: The study outcomes were short-term postoperative, functional, and oncologic outcomes. Regression models investigated the effect of surgical approach (open vs Robot assisted) on study outcomes, and interaction tests were used for subgroup analyses. Propensity score matching for demographic and tumor characteristics was used in sensitivity analyses. Multivariable Cox-regression analyses identified predictors of oncologic outcomes after RAPN. Results and limitations: Baseline characteristics were similar between patients receiving RAPN and OPN, with only few differences. After adjusting for confounding, RAPN was associated with lower odds of intraoperative (odds ratio [OR]: 0.39, 95% confidence interval [CI]: 0.22, 0.68) and Clavien-Dindo ≥2 postoperative (OR: 0.29, 95% CI: 0.16, 0.50) complications (both p < 0.05). This association was not affected by comorbidities, tumor dimension, PADUA score, or preoperative renal function (all p > 0.05 on interaction tests). On multivariable analyses, we found no differences between the two techniques with respect to functional and oncologic outcomes (all p > 0.05). Overall, there were 63 and 92 local recurrences and systemic progressions, respectively, with a median follow-up after surgery of 32 mo (interquartile range: 18, 60). Among patients receiving RAPN, we assessed predictors of local recurrence and systemic progression with discrimination accuracy (ie, C-index) that ranged from 0.73 to 0.81. Conclusions: While cancer control and long-term renal function did not differ between RAPN and OPN, we found that the intra- and postoperative morbidity—especially in terms of complications—was lower after RAPN than after OPN. Our predictive models allow surgeons to estimate the risk of adverse oncologic outcomes after RAPN, with relevant implications for preoperative counseling and follow-up after surgery. Patient summary: In this comparative study on robotic versus open partial nephrectomy, functional and oncologic outcomes were similar between the two techniques, with lower morbidity—especially in terms of complications—for robot-assisted surgery. The assessment of prognosticators for patients receiving robot-assisted partial nephrectomy may help in preoperative counseling and provides relevant data to tailor postoperative follow-up.