Risk classification system using the detailed positive surgical margin status for predicting biochemical recurrence after robot-assisted radical prostatectomy.

Aim: This study aimed to evaluate the risk classification system using the detailed positive surgical margin (PSM) status to predict biochemical recurrence (BCR) after robot-assisted radical prostatectomy (RARP).

Methods: We retrospectively analyzed 427 patients who underwent RARP between January 2016 and March 2020. We investigated risk factors for BCR using univariate and multivariate Cox proportional hazard regression models. The biochemical recurrence-free survival (BRFS) rate was assessed using the Kaplan-Meier method.

Results: The median follow-up period was 43.4 months and 99 patients developed BCR. In the multivariate analysis, maximum PSM length > 5.0 mm and the International Society of Urological Pathology grade group (ISUP GG) at the PSM ≥3 were predictive factors for BCR in patients with a PSM. In the multivariate analysis, these factors were also independent predictive factors in the overall study population, including patients without a PSM. We classified the patients into four groups using these factors and found that the 1-year BRFS rates in the negative surgical margin (NSM) group, low-risk group (PSM and neither factor), intermediate-risk group (either factor), and high-risk group (both factors) were 94.9%, 94.5%, 83.1%, and 52.9%, respectively. The low-risk group showed similar BRFS to the NSM group (p = 0.985), while the high-risk group had significantly worse BRFS than the other groups (p < 0.001).

Conclusion: Maximum PSM length > 5.0 mm and ISUP GG at the PSM ≥3 were independent predictive factors for BCR after RARP. Risk classification for BCR using these factors is considered to be useful and might help urologists decide on additional treatment after RARP.