Timo Soeterik

163 General Summary fulfilling all PRIAS inclusion criteria, whereas stringent follow-up remains advised in PRIAS-ineligible patients. PART II. IMPACT OF MRI ON PROSTATE CANCER RISK CLASSIFICATION In the study described in Chapter 4, we observed that multiparametric magnetic resonance imaging (mpMRI) has superior detection of non-organ-confined disease (stage ≥T3a), compared with DRE. Use of mpMRI T-stage for prostate cancer risk group classification leads to upstaging in one-third of patients. Overall, use of mpMRI resulted in a 9% higher cumulative rate of true positive and true negative stage ≥T3a test results compared with DRE. Since mpMRI results in a higher overall diagnostic accuracy for the detection of non-organ-confined disease, it should be preferred over DRE for determining clinical tumour stage. However, due to its limited specificity for the detection of non- organ-confined disease, clinicians should be aware that mpMRI can lead to overstaging and potential overtreatment of patients who harbor genuine low-risk disease. PART III. ASSOCIATION BETWEEN NERVE SPARING AND POSITIVE SURGICAL MARGINS Chapter 5 includes the description of an extensive multivariable analysis, using side- specific covariates, evaluating the association between nerve sparing robot-assisted radical prostatectomy (RARP) and the risk of positive margins. In this multi-centre cohort, including analysis of 5148 prostate lobes derived from 2574 patients, nerve sparing was an independent predictor for ipsilateral positive margins (OR 1.42, 95% CI 1.14 – 1.82) on multivariable analysis. Our study results call into question the classic assumption that nerve sparing is not associated with an increased risk of positive surgical margins. The study’s main finding is relevant for clinical practice, as patients and their urologists need to be aware of the fact that nerve sparing does increase the risk of positive margins. The potential benefits of nerve sparing should therefore be carefully weighed against the concomitant risks when consulting patients opting for nerve sparing radical prostatectomy. PART IV. INCORPORATION OF MRI INTO CLINICAL PREDICTION MODELS Since MRI has the potential to improve the predictive ability of nomograms, it should be evaluated if incorporation of MRI information into nomograms combined with traditional characteristics such as PSA and biopsy data can improve side-specific 9