Prognostic differences among the positive surgical margin locations following robot-assisted radical prostatectomy in a large Japanese cohort (the MSUG94 group)

To investigate whether subgroups of prostate cancer patients, stratified by positive surgical margin locations, have different oncological outcomes following robot-assisted radical prostatectomy.A retrospective multicenter cohort study in prostate cancer patients undergoing robot-assisted radical prostatectomy was conducted at 10 institutions in Japan. Pre- and post-operative outcomes were collected from enrolled patients. Biochemical recurrence and clinical and pathological variables were evaluated among subgroups with different positive surgical margin locations.A total of 3195 patients enrolled in this study. Data from 2667 patients (70.1% [N = 1869] with negative surgical margins and 29.9% [N = 798] with positive surgical margins based on robot-assisted radical prostatectomy specimens) were analyzed. The median follow-up period was 25.0 months. The numbers of patients with apex-only, middle-only, bladder-neck-only, seminal-vesicle-only and multifocal positive surgical margins were 401, 175, 159, 31 and 32, respectively. In the multivariate analysis, PSA level at surgery, pathological Gleason score based on robot-assisted radical prostatectomy specimens, pathological T stage, pathological N stage and surgical margin status were independent risk factors significantly associated with biochemical recurrence-free survival. Patients undergoing robot-assisted radical prostatectomy with multifocal positive surgical margins and seminal-vesicle-only positive surgical margins were associated with worse biochemical recurrence-free survival than those with apex-only, middle-only and bladder-neck-only positive surgical margins. Patients undergoing robot-assisted radical prostatectomy with apex-only positive surgical margins, the most frequent positive surgical margin location, were associated with more favorable biochemical recurrence-free survival that those with middle-only and bladder-neck-only positive surgical margins. The study limitations included the lack of central pathological specimen evaluation.Although positive surgical margin at any locations is a biochemical recurrence risk factor after robot-assisted radical prostatectomy, positive surgical margin location status should be considered to accurately stratify the biochemical recurrence risk after robot-assisted radical prostatectomy.