Prognostic value of unifocal and multifocal positive surgical margins in a large series of robot-assisted radical prostatectomy for prostate cancer

Purpose To evaluate the prognostic value of positive surgical margins (PSM) focality for the prediction of biochemical recurrence (BCR) in patients undergoing robotic-assisted radical prostatectomy (RARP) for prostate cancer. Methods All men with clinically localized prostate cancer undergoing RARP in our tertiary referral centre between May 2005 and August 2016 were retrospectively identified. Patients with neoadjuvant therapy were excluded. Comparisons were made between cases with negative surgical margins (NSM), unifocal PSM (uPSM), and multifocal PSM (mPSM). Results From a total of 973 patients available for analysis, 315 (32%) had a PSM. In these patients, 190 had uPSM and 125 had mPSM. Focality of PSM was significantly associated with tumour stage and grade, preoperative PSA, and postoperative PSA persistence (all p < 0.001), but not with nerve sparing (NS) (p = 0.15). PSA persistence was found in 120 (12%) patients, resulting in 853 patients available for survival analyses with a median follow-up of 52 months. Both uPSM and mPSM were found to be independent predictors of BCR, conferring a hazard ratio of 1.9 (95% CI 1.3-3.0; p = 0.002) and 3.4 (95% CI 2.1-5.6; p < 0.001), respectively, when compared to NSM. In subgroup analyses, PSM was particularly predictive for BCR when patients underwent unilateral or bilateral NS (p <= 0.003). Conclusions Based on a large case series of RARP, we found PSM focality to be an independent predictor of BCR, with a 1.9- and 3.4-fold risk increase for BCR in case of uPSM and mPSM, respectively. PSM seems to be of particular prognostic relevance when NS has been performed.