Timo Soeterik

64 CHAPTER 4 METHODS Study population and data collection This study was conducted within the Santeon consortium, which consists of 7 teaching hospitals in the Netherlands. After receiving institutional review board approval, data was extracted from the prospectively maintained Santeon database containing baseline tumour characteristics (baseline PSA, biopsy International Society of Urological Pathology [ISUP] grade, 13 clinical T-stage assessed by DRE, mpMRI T-stage, prostate volume, choice of treatment, surgical outcomes and PSA follow-up). Patients newly diagnosed with clinically localised or locally advanced prostate cancer (any T, any N, M0), between January 1 st , 2017 and December 31 st , 2018 who underwent mpMRI were included for analysis. Variable and outcome definitions The DRE was performed by a senior resident or urologist during the primary staging work-up. MpMRI T-stage was retrieved from the radiology reports. MpMRI was performed either pre-biopsy or a minimum of 6 weeks after biopsy. The MRI protocols of the seven Santeon hospitals are presented in Table S1. Radiological reporting was done according to the PI-RADS Version 2. 14 Presence of non-organ-confined disease included reported suspicion of extraprostatic extension, seminal vesicle invasion and/ or invasion to organs adjacent to the prostate (stage ≥T3a). Surgical pathology reporting was performed according to the ISUP guidelines. 15 Impact of mpMRI on risk group classification and treatment intensification Patients were classified into risk groups according to the European Association of Urology (EAU) classification system, using clinical T-stage assessed by DRE: low-risk (T1 or T2a, PSA ≤ 10 ng/mL and ISUP 1), intermediate-risk (T2b, PSA 10 – 20 ng/mL, ISUP 2 or 3), localised high-risk (T2c or higher, PSA > 20 ng/mL or ISUP > 3) and locally advanced high-risk (T3a or higher and PSA > 20 ng/mL or ISUP > 3). Patients were also classified using the mpMRI T-stage. Number of patients that migrated to either a lower or higher risk group based on mpMRI findings was established. In patients who underwent external beam radiation therapy (EBRT), the consequence of upstaging by mpMRI results for treatment advice was defined as addition of androgen deprivation therapy to EBRT. Rates of treatment intensification were compared for patients with and without upstaging due to mpMRI information.