Timo Soeterik

62 CHAPTER 4 ABSTRACT Background: The currently recommended prostate cancer risk classification system, including digital rectal examination (DRE) for local staging, is the cornerstone to guide clinical decision-making. Although multiparametric magnetic resonance imaging (mpMRI) has potential benefits over DRE with regard to local tumour staging, its impact on risk group classification and treatment selection is unclear. Therefore, we will assess the impact of mpMRI local tumour staging on prostate cancer risk stratification and choice of treatment. Methods: Prostate cancer patients, newly diagnosed from 2017 to 2018 at 7 Dutch teaching hospitals were included. Risk group classification was done twice, using either DRE or mpMRI information. Risk group migration and rates of treatment intensification associated with mpMRI upstaging were established. Diagnostic accuracy measures for the detection of non-organ-confined disease (stage ≥T3a), for both DRE and mpMRI, were assessed in patients undergoing robot-assisted radical prostatectomy. Results: A total of 1683 patients were included. Upstaging due to mpMRI staging occurred in 493 of 1683 (29%) patients and downstaging in 43 of 1683 (3%) patients. Upstaging was associated with significant higher odds for treatment intensification (odds ratio [OR]: 3.5 95% confidence interval [CI] 1.9 - 6.5). Stage ≥T3a on mpMRI was the most common reason for risk group upstaging (77%). Sensitivity for the detection of stage ≥T3a was higher for mpMRI compared to DRE (51% vs 12%, p < 0.001), whereas specificity was lower (82% vs 97%, p < 0.001). mpMRI resulted in a significantly higher cumulative rate of true positive and true negative stage ≥T3a predictions compared with DRE (67% vs 58%, p < 0.001). Conclusions: Use of mpMRI tumour stage for prostate cancer risk classification leads to migration to a higher risk group in 1 of 3 patients. mpMRI enables superior detection of non-organ-confined disease compared with DRE and should be the preferred tool for determining clinical tumour stage.