Background: Robotic-assisted prostatectomy (RAP) is a costly process to adopt, and these costs have been analyzed; however the learning curve of RAP has not been similarly scrutinized. Our purpose is to model the cost of learning RAP.
Methods: We developed a literature-based model that assumed a surgeon’s first RAP lasts eight hours and after mastery of the learning curve, the surgeon completes a RAP in three or four hours. Based on literature estimates, improvement between cases of one, five or 10 minutes was modeled. The nadir in operative time was considered a surrogate for the end of the learning curve, thus the number of cases between the first case and the nadir operative time is the length of the learning curve. The cost of the learning curve equals the average published cost of operating room time from several centers, $10.50 per minute, multiplied by the length of the learning curve in minutes.
Results: Twenty-four cases are required in order to achieve a four-hour RAP, when operative time decreases by 10 minutes per case; this is compared to the 300 cases needed to achieve a goal operative time of three hours, assuming one minute of improvement between cases (Figure 1). This translates to costs ranging from a low of $95,000 with improvement of 10 minutes per case and a four-hour RAP, to a high of $1,047,000 for a three-hour RAP with one minute of improvement per case. Figure one also displays these data.
Figure one: The Cost of the Learning Curve for Robotic-assisted Prostatectomy
Conclusions: Published estimates of the RAP learning curve range from 30 to 300 cases, amounting to a $940,000 difference in costs. Clearly swift mastery of RAP is less costly than a lengthy learning process. A surgeon who improves 10 minutes per case, as opposed to one minute per case, saves $816,000 to $940,000, depending on his ultimate operative time.
Our model only accounts for the costs of operating room (OR) time and anesthesia time, and does not consider complication rates, transfusion rates or length of hospitalization. These factors are considered negligible relative to the costs of the OR and anesthesia. Our model also does not account for whether a surgeon is transitioning from conventional open retropubic prostatectomy or laparoscopic prostatectomy to RAP.
Since the average urologist performs 10-15 prostatectomies per year, even a short learning curve of 24 or 30 cases may not be traversed within the first year or two of ownership of a daVinci robot. In addition to the costs of the robot, service contract, and instruments, the cost and length of the learning curve should be considered when adopting RAP.