Timo Soeterik

141 MRI T-stage for LNI Risk Prediction BACKGROUND Assessment of pelvic lymph node involvement (LNI) by extended pelvic lymph node dissection (ePLND) is an essential component of the general staging work-up in patients with newly diagnosed prostate cancer selected for radical prostatectomy, and is indicated in patients with a risk of LNI above 5%. 1 Even minimal tumour involvement of the lymphatic system is thought to have pivotal impact on disease prognosis, and should be established to identify patients with an increased risk of disease recurrence. 2 Currently, the field of clinical imaging, particularly prostate-specific membrane antigen (PSMA) positron-emission tomography/computer tomography (PET-CT), is rapidly evolving. However, since the sensitivity of PSMA PET-CT for the detection of LNI in primary prostate cancer is only moderate, it cannot yet replace ePLND to exclude LNI. 3,4 Thus, ePLND remains the preferred option for nodal staging in primary prostate cancer. 1 However, performing ePLND in patients undergoing radical prostatectomy is associated with unfavourable intraoperative and perioperative outcomes, including symptomatic lymphocele development (in up to 18%), bleeding (2.7%), infections (3.6%), and ureteral damage (0.8%), whereas there is no high-level evidence for a direct therapeutic effect. 5,6 Therefore, ePLND should be reserved for carefully selected patients. Both the European Association of Urology (EAU) and the National Comprehensive Cancer Network (NCCN) guidelines recommend the use of nomograms to guide patient selection for ePLND. 1,7 Several of these prediction tools have been developed over the years. 8 The Memorial Sloan Kettering Cancer Centre (MSKCC) pre-radical prostatectomy (update 2018) and Briganti 2012 nomograms are the two most established models. 9,10 In a recent validation study using a contemporary cohort of patients with Prostate cancer, the 2012 Briganti and the 2018 MSKCC nomograms were identified as the most accurate prediction tools available, with a reported area under the curve (AUC) of 0.76 and 0.75, respectively. 8 Both the MSKCC 2018 and Briganti 2012 nomograms include clinical tumour (T-stage) assessed by digital rectal examination (DRE) as one of the input parameters. 9,10 However, recent guideline updates include the recommendation for performing multiparametric MRI (mpMRI) prior to prostate biopsy. 1,11 As a result, mpMRI staging information will become standardly available in newly diagnosed patients. In addition, mpMRI potentially enables a more accurate estimation of local tumour extent compared with DRE. 12 However, it is not clear if the use of T-stage assessed by mpMRI (mpMRI T-stage) results in more accurate nomogram-based LNI risk prediction. In the present study, therefore, we evaluate whether replacing DRE T-stage by mpMRI T-stage results in a more accurate LNI risk prediction by the MSKCC 2018 and Briganti 2012 nomograms. 8