LAUSR

MRI of the prostate is associated with a high negative predictive value (NPV) for clinically significant prostate cancer (csPCa). However, not in all studies negative mp-MRI had negative back-up histology. Moreover, there is a lack of strong data on follow-up in men with initial negative evaluation. The aim of this study was to assess the outcome over time of men with negative mp-MRI and a proven absence of PCa at initial systematic biopsy. METHODS: We evaluated 250 patients with negative mp-MRI (PIRADS 1 or 2) and a concomitant negative systematic prostate biopsy performed at a single tertiary care referral centre between 2016 and 2017. All patients were submitted to 1.5 MRI study using an endorectal coil which was interpreted by two expert radiologists. After negative imaging and biopsy, all patients were then followed with annual serial PSA measurement and digital rectal examination (DRE). In case of suspicion for PCa (rising PSA and/or positive DRE), follow-up mp-MRI and/or prostate biopsy (Bx) were performed. The study outcome was csPCa (defined as Gleason score at biopsy 3þ4) during follow-up. Kaplan Meier analysis was used to assess csPCa diagnosis-free survival. Using multivariable Cox regression analysis (MVA) we investigated eventual predictors of presence of csPCa at follow-up using the following covariates: age at biopsy, PSA density and clinical stage (T1 vs T2 vs T3). RESULTS: Median follow-up was 30 months (IQR: 23-41). During the study period, 49 men (19.6%) underwent mp-MRI and 41 (16.4%) received a follow-up Bx. Overall, 5% (13/250) patients had positive MRI (PI-RADS 3-5) over time. Of all patients, 33 (13.2%) and 13 (5.2%) had any PCa and csPCa, respectively at follow-up after initial negative mp-MRI. The 2-, 3and 4-year csPCa diagnosis-free survival were 94.6, 87.8 and 86%, respectively. Diagnosis-free survival probability for csPCa was unchanged after 48 months of follow-up onwards. At MVA, none of the predictors investigated was significantly associated with csPCa findings during follow-up in men with initial negative mpMRI (all p 0.1). CONCLUSIONS: We demonstrated that only a minority of patients (5%) with initial negative mpMRI and concomitant negative Bx developed csPCa at a median follow-up of 30 months, suggesting how the high initial NPV of mp-MRI is maintained over time. These findings support the importance of initial negative mp-MRI in ruling out csPCa over time provided a negative initial biopsy.