Is off‐clamp robot‐assisted partial nephrectomy beneficial for renal function? Data from the CLOCK trial.

Objectives: To compare the functional outcomes of on‐ vs off‐clamp robot‐assisted partial nephrectomy (RAPN) within a randomized controlled trial (RCT). Materials and Methods: The CLOCK study (CLamp vs Off Clamp the Kidney during robotic partial nephrectomy; NCT 02287987) is a multicentre RCT including patients with normal baseline function, two kidneys and masses with RENAL scores ≤ 10. Pre‐ and postoperative renal scintigraphy was prescribed. Renal defatting and hilum isolation were required in both study arms; in the on‐clamp arm, ischaemia was imposed until the completion of medullary renorraphy, while in the off‐clamp condition it was not allowed throughout the procedure. The primary endpoint was 6‐month absolute variation in estimated glomerular filtration rate (AV‐GFR); secondary endpoints were: 12, 18 and 24‐month AV‐GFR; 6‐month estimated glomerular filtration rate variation >25% rate (RV‐GFR >25); and absolute variation in ipsilateral split renal function (AV‐SRF). The planned sample size was 102 + 102 cases, after taking account crossover of cases to the alternate study arm; a 1:1 randomization was performed. AV‐GFR and AV‐SRF were compared using analysis of covariation, and RV‐GFR >25 was assessed using multivariable logistic regression. Intention‐to‐treat (ITT) and per‐protocol analyses (PP) were performed. Results: A total of 160 and 164 patients were randomly assigned to on‐ and off‐clamp RAPN, respectively; crossover was observed in 14% and 43% of the on‐ and off‐clamp arms, respectively. We were unable to find any statistically significant difference between on‐ vs off‐clamp with regard to the primary endpoint (ITT: 6‐month AV‐GFR −6.2 vs −5.1 mL/min, mean difference 0.2 mL/min, 95% confidence interval [CI] −3.1 to 3.4 [P = 0.8]; PP: 6‐month AV‐GFR −6.8 vs −4.2 mL/min, mean difference 1.6 mL/min, 95% CI −2.3 to 5.5 [P = 0.7]) or with regard to the secondary endpoints. The median warm ischaemia time was 14 vs 15 min in the ITT analysis and 14 vs 0 min in the PP analysis. Conclusion: In patients with regular baseline function and two kidneys, we found no evidence of differences in functional outcomes for on‐ vs off‐clamp RAPN. [ABSTRACT FROM AUTHOR]