Timo Soeterik

164 CHAPTER 9 extraprostatic extension (EPE) risk prediction. Martini and colleagues have developed such a nomogram, and concluded that it can lead to reliable prediction of side-specific EPE in patients undergoing RARP. To determine if this nomogram can be safely applied in other populations, we performed an external validation of the Martini nomogram for the prediction of side-specific EPE ( Chapter 6 ). Although external validation showed good discrimination in terms of AUC (0.78), the model showed substantial disagreement between predicted and observed probabilities on the calibration plots. Use of a miscalibrated nomogram (either underestimation or overestimation) can be potentially harmful for patients. Therefore, we concluded that based on this external validation study, the Martini nomogrammay not be a suitable prediction tool to predict side-specific EPE in patients undergoing RARP. In Chapter 7, we describe the outcomes of a study in which we developed and externally validated four nomograms for the prediction of side-specific EPE, using combinations of PSAD, highest ipsilateral biopsy International Society of Urological Pathology (ISUP) grade, ipsilateral percentage of positive cores on systematic biopsy and side-specific clinical stage assessed by both digital rectal examination and mpMRI. The three models including mpMRI staging information resulted in relatively higher AUCs compared with the model without mpMRI information. The model based on PSAD, ISUP grade and mpMRI T-stage was superior in terms of model calibration. Using this model with a cut-off of 20%, 1980/2908 (68%) of all prostatic lobes without EPE would be found eligible for nerve sparing, whereas non-nerve sparing would be advised in 642/832 (77%) lobes with EPE. Our study resulted in a simple and robust nomogram, including mpMRI information and readily available clinical parameters, for the prediction of side-specific EPE. This nomogram can be safely used in clinical practice and can potentially improve patient selection for nerve sparing radical prostatectomy. In Chapter 8 , we evaluated the impact of using mpMRI T-stage on the diagnostic accuracy of two commonly used nomograms (MSKCC 2018 and Briganti 2012) for the prediction of pelvic lymph node involvement (LNI) in patients with prostate cancer undergoing extended pelvic lymph node dissection. We concluded that use of mpMRI T-stage improved model discrimination of both nomograms, compared with DRE T-stage. Model calibration was comparable for both modalities. Use of mpMRI T-stage and the Briganti 2012 nomogram resulted in the overall best model performance in terms of discrimination, calibration and net benefit. These results are important, since scientific data regarding the use of mpMRI T-stage for nomogram-based LNI risk prediction by existing nomograms are scarce. Based on the study’s main results, we can conclude that mpMRI T-stage can be safely used as an input parameter for nomogram-based LNI risk prediction.