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Background and objective: Positive surgical margins (PSMs) following radical prostatectomy (RP) have been seen as inherently unfavorable. However, a large international multi-institutional study recently revealed that unifocal PSMs (UPSMs) had no impact on prostate cancer–specific mortality (PCSM), whereas multifocal PSMs (MPSMs) did. Our aim was to assess the relative impact of PSMs versus percentage tumor volume (PTV) on PCSM. Methods: We analyzed data for 1552 patients who underwent robot-assisted RP performed by a single surgeon between 2002 and 2018 at a tertiary referral center with up to 15-yr follow-up. Patients were divided into negative surgical margin (NSM), UPSM, and MPSM groups, with PTV stratification using a cutoff of 40%. The primary outcome was stepwise multivariate regression analysis of predictors of PCSM (pT stage, pathological Gleason grade group, PTV, UPSM, and MPSM). The secondary outcome was the risk of 15-yr PCSM via Kaplan-Meier analysis. Key findings and limitations: The group with 40–100% PTV was older and presented with more advanced grade and stage. High PTV was significantly associated with greater risk of PSM, biochemical recurrence, PCSM, and overall mortality at 15 yr (p