Surgical margin status is commonly used as an end point for surgical learning. We examined the surgical margin learning curve and investigated whether surgical margins are a good marker for oncological outcome.
The study cohort included 7,765 patients with prostate cancer treated with radical prostatectomy by 1 of 72 surgeons at a total of 4 major American academic medical centers. We calculated the learning curve for surgical margins and a concordance probability between the surgeon rates of positive surgical margins and 5-year biochemical recurrence.
A positive surgical margin was identified in 2,059 patients (27%). On multivariate analysis surgeon experience was strongly associated with surgical margin status (p = 0.017). The probability of a positive surgical margin was 40% for a surgeon with 10 prior cases, which decreased to 25% for a surgeon with 250 (absolute difference 15%, 95% CI 11 to 18). Learning curves differed dramatically among surgeons. For surgeon pairs the surgeon with the superior positive surgical margin rate also had the better biochemical recurrence rate only 58% of the time.
We noted a learning curve for surgical margins after open radical prostatectomy. The poor concordance between surgeon margin and recurrence rates suggests that while margins clearly matter and efforts should be made to decrease positive margin rates, surgical margin status is not a strong surrogate for cancer control. These results have implications for using the margin rate to evaluate changes in surgical technique and as surgeon feedback.