Linear extent of positive surgical margin impacts biochemical recurrence after robot-assisted radical prostatectomy in a high-volume center

The objective of this study is to evaluate if surgeon volume and stratifying positive surgical margins (PSM) into focal and non-focal may differentially impact the risk of biochemical recurrence (BCR) after robot-assisted radical prostatectomy (RARP). Between January 2013 and December 2017, 732 consecutive patients were evaluated. The population included negative cases (control group) and PSM subjects (study group). PSMs were stratified as focal (≤ 1 mm) or non-focal (> 1 mm). A logistic regression model assessed the independent association of factors with the risk of PSM. The risk of BCR of PSM and other factors was assessed by Cox's multivariate proportional hazards. Overall, 192 (26.3%) patients had PSM focal in 133 patients; non-focal in 59 cases. Focal PSM was associated with the percentage of biopsy positive cores (BPC; OR 1.011; p = 0.015), extra-capsular extension (pT3a stage; OR 2.064; p = 0.016), seminal vesicle invasion (pT3b; OR 2.150; p = 0.010), body mass index (odds ratio, OR 0.914; p = 0.006), and high surgeon volume (OR 0.574; p = 0.006). BPC (OR 1.013; p = 0.044), pT3a (OR 4.832; p < 0.0001) and pT3b stage (OR 5.153; p = 0.001) were independent predictors of the risk of non-focal PSM. Surgeon volume was not a predictor of non-focal PSM (p = 0.224). Independent factors associated with the risk of BCR were baseline PSA (hazard ratio, HR 1.064; p = 0.004), BPC (HR 1.015; p = 0.027), ISUP biopsy grade group (BGG) 2/3 (HR 2.966; p 0.003) and BGG 4/5 (HR 3.122; p = 0.022) pathologic grade group 4/5 (HR 3.257; p = 0.001), pT3b (HR 2.900; p = 0.003), and non-focal PSM (HR 2.287; p = 0.012). Surgeon volume was not a predictor of BCR (p = 0.253). High surgeon volume is an independent factor that lowers the risk of focal PSM. Surgeon volume does not affect non-focal PSM and BCR. Negative as well as focal PSM are not associated with BCR.