Cumulative sum analysis of learning curve for video-assisted mini-laparotomy partial nephrectomy in renal cell carcinoma

Abstract

Video-assisted mini-laparotomy surgery (VAMS), a hybrid of open and laparoscopic surgical techniques, is an important surgical approach in the field of partial nephrectomy. The learning curve for VAMS partial nephrectomy has not been studied to date; we therefore, evaluated this learning curve.We prospectively evaluated 20 consecutive patients who underwent VAMS partial nephrectomy performed by a single surgeon (YEY) between March 2015 and December 2016. The learning curve was evaluated using the cumulative sum method. The measure of surgical performance was composed of 3 parameters (total operation time [Op time], warm ischemic time [WIT], and estimated blood loss [EBL]).Among the 20 patients who underwent VAMS partial nephrectomy, the mean age was 54.6 years. The mean Op time and WIT were 172.5 and 28.8 minutes, respectively. The learning curve for the Op time, WIT, and EBL consisted of 3 unique phases: phase 1 (the first 7 cases), phase 2 (the next 5 to 7 cases), and phase 3 (all subsequent cases). Phase 1 represents the initial learning curve, and the phase 2 plateau represents the period of expert competency. Phase 3 represents when one is competent in VAMS partial nephrectomy.The learning curve for VAMS partial nephrectomy is relatively short and after a learning curve of approximately 7 cases, the surgeon became familiar with VAMS partial nephrectomy; after 12 to 14 cases, the surgeon became competent in this procedure.

Figure 1

Operative setup for VAMS. VAMS = video-assisted mini-laparotomy surgery.

Figure 2

Total operation time (black) and CUSUM_OT (blue line) plotted against case number; the red line represents the best fit curve for the plot, which is a second-order polynomial with the equation CUSUM_OT = –1.24 × case number² + 19.002 × case number + 62.238 (R² = 0.6098). Three phases were identified based on total operation time in terms of the CUSUM learning curve. CUSUM = cumulative sum.

Figure 3

Warm ischemic time (black) and CUSUM_WIT (blue line) plotted against case number; the red line represents the best fit curve for the plot, which is a second-order polynomial with the equation CUSUM_WIT = –0.1618 × case number² + 1.9719 × case number + 20.233 (R² = 0.5607). Three phases were identified based on warm ischemic time in terms of the CUSUM learning curve. CUSUM = cumulative sum.

Figure 4

Estimated blood loss (black) and CUSUM_EBL (blue line) plotted against case number; the red line represents the best fit curve for the plot, which is a second-order polynomial with the equation CUSUM_EBL = –10.133 × case number² + 204.13 × case number – 164.53 (R² = 0.7978). Three phases were identified based on estimated blood loss in terms of the CUSUM learning curve. CUSUM = cumulative sum.