Timo Soeterik

17 General Introduction and Thesis Outline FIGURE 2. Extraprostatic extension on magnetic resonance imaging and histopathological whole mount section A. Magnetic resonance imaging (T2), tumour stage classified as “organ confined”. B. Whole mount section after radical prosta- tectomy revealing extraprostatic extension (arrow). Value of MRI in risk classifications and nomograms The current EAU guidelines recommend the use of a risk classification system, based on the D’Amico classification, using DRE to determine cT. 17 The outcomes of DRE are crucial, and subtle differences in DRE findings determine the risk group a patient is assigned to (e.g. cT2a [low-risk] vs. cT2b [intermediate-risk]). Because MRI enables visualization of the prostate gland in total, whereas with DRE the prostate can only be evaluated dorsally, definition of the cT may be more accurate when using MRI information. For example, risk classification by means of cT assessed by DRE is associated with the risk of understaging and subsequent undertreatment of prostate cancer. 36 Although MRI may eventually improve local tumour staging, there is a lack of suitable studies providing information on the impact of using the cT assessed by prostate MRI. Therefore, the current standpoint includes that although MRI provides significant additional information, it cannot replace DRE as the clinical staging standard. 37 The most established clinical nomograms used for the prediction of unfavourable histopathological outcomes after surgery, including prediction of EPE and pelvic lymph node involvement (LNI), also include cT assessed by DRE. 38 MpMRI information could also improve clinical risk prediction models; as mpMRI local staging information is potentially more robust compared to local staging information assessed by DRE. Thus, the combined value of mpMRI information and the traditional clinical parameters in nomograms may enhance risk prediction of unfavourable histopathological outcomes. Preliminary findings on this topic are promising, as two separate study groups observed significant increases in model discrimination in terms of area under the curve after incorporation of MRI information, for commonly used tools including the MSKCC pre-radical prostatectomy nomogram. 39,40 The potential benefit of using mpMRI clinical staging information, 1