Preoperative multiparametric MRI does not lower positive surgical margin rate in a large series of patients undergoing robot-assisted radical prostatectomy.

To optimize functional outcomes after robot-assisted radical prostatectomy (RARP), surgical preservation of the neurovascular bundle is desired. However, nerve-sparing surgery (NSS) is only feasible in the absence of extraprostatic tumour extension (T-stage 3) to avoid the risk of positive surgical margins (PSM). Multiparametric magnetic-resonance imaging (MRI) is increasingly performed for primary prostate cancer and provides information on local tumour stage. In this study, we evaluated whether the availability of information from MRI influenced the incidence of PSM. A total of 523 patients undergoing RARP for localized prostate cancer in a single Dutch reference centre for prostate-cancer surgery were retrospectively evaluated (2013-2017). Patient characteristics and postoperative outcomes were retrieved. Patients were stratified according to the presence of a preoperative MRI. The incidence of PSM and proportion of patients receiving NSS was analysed using Chi-square tests and logistic regression analysis. N = 139 of 523 (26.6%) patients had a preoperative MRI scan available. Patients with MRI had identical preoperative characteristics compared to the patients without MRI, except for a higher percentage of patients having a prostate-specific antigen value ≥ 20 ng/mL (20.1% versus 9.4%, p = 0.004). PSM were present in 107/384 (27.9%) patients without MRI compared to 36/139 (25.9%) patients with an MRI scan before surgery (p = 0.66). Unilateral NSS was performed more often in the MRI group (26.6% vs. 11.7%), but NSS on both sides was more frequently performed in patients without MRI (57.6% versus 69.8%) (p < 0.001). MRI was not associated with PSM in multivariate analysis (p = 0.265). Preoperative mpMRI imaging was not associated with lower rates of positive surgical margins in patients undergoing RARP for localized prostate cancer.