"Learning curve" may not be enough: assessing the oncological experience curve for robotic radical prostatectomy

The use of robot-assisted laparoscopic radical prostatectomy (RALP) is widespread in the community. A definitive RALP "learning curve" has not been defined and existing learning curves do not account for urologists without prior advanced laparoscopic skills. Therefore, an easily evaluable metric, the "oncological experience curve," would be clinically useful to all urologists performing RALP. Positive surgical margin (PSM) status for all subjects undergoing RALP during the first 4 years of a single surgeon's experience was assessed. Univariate and multivariate analyses and logistic regression identified predictors of PSM creation and their correlation with surgeon case volume. The oncological experience curve was defined as the case point at which only pT2 stage, not surgeon volume (and thus surgeon inexperience), predicted PSM in the logistic regression. A total of 469 consecutive subjects comprised our cohort. Overall pT2 and pT3 PSM rates were 20% and 40%, respectively. Preoperative prostate-specific antigen, pathologic stage, and year of surgery were associated with PSM occurrence. Pathologic stage exclusively correlated to PSM in pT2 specimens for the first time during the fourth year, after 290 subjects had been treated. pT2 PSM rate before and after Case 290 was 25% and 10%, respectively (p < 0.001). The oncological experience curve is a clinically meaningful measure to evaluate the RALP learning curve for non-fellowship-trained urologists. The oncological experience curve may be much longer than the previously reported learning curves. Surgeons should consider whether they can build enough experience to minimize suboptimal oncological outcomes before embarking on or continuing a RALP program.