Mastering Single Port Robot-Assisted Partial Nephrectomy with the Low Anterior Access: A Learning Curve Analysis with Comparison of Perioperative Outcomes

Abstract

Introduction:

Single port (SP) robot-assisted partial nephrectomy (RAPN) can be successfully performed via an extraperitoneal low anterior access (LAA), with the patient in a supine position. To our knowledge, no data on the learning curve (LC) of SP RAPN performed with the LAA are available in the literature.

Methods:

Supine LAA SP RAPNs performed by a single experienced SP surgeon from 2019 to 2025 were retrospectively reviewed. A cumulative summation (CUSUM) methodology in terms of operative time was used for the assessment of the surgical learning curve. After identifying the number of cases required for proficiency achievement, a comparison of perioperative and postoperative outcomes of the learning and proficiency phases was conducted.

Results:

After determining the CUSUM value for each of the 66 included cases, a cubic polynomial regression with a high goodness of fit coefficient (R² = 0.987) was adopted to plot the LC. The resulting third-degree polynomial equation was solved to extract the inflection point of the curve, representing the case threshold for achieving competence, which corresponded to the 33rd case. The learning curve was accordingly divided into a learning phase (cases 1–33) and a proficiency phase (cases 34–66) to compare perioperative and postoperative outcomes. Preoperative tumor and patient characteristics were similar between the groups. Procedures performed in the learning phase demonstrated significantly longer median operative times (210 minutes [interquartile range [IQR] 175–250] vs 164 minutes [IQR 148.5–202.5], p < 0.001) and ischemia times (26 minutes [20.5–31.5] vs 19 minutes [17.5–22], p < 0.001) and lower rates of trifecta achievement (n = 16 [48.5%] vs n = 26 [78.8%], p = 0.01). Finally, at multivariate analysis, being operated in the proficiency phase was independently and significantly associated with a higher likelihood of trifecta achievement (odds ratio: 8.53, 95% confidence interval 1.6–45.6, p = 0.012).

Conclusions:

The LC of LAA SP RAPN can be mastered safely with a relatively attainable number of cases by an experienced robotic surgeon.