Clinical implications of prostatic capsular abutment or bulging on multiparametric magnetic resonance imaging

Background: The presence of capsular abutment or bulging can raise concern when planning surgery. In this study we aimed to test the clinical implications of capsular abutment or bulging on preoperative multiparametric magnetic resonance imaging (mpMRI). Methods: We analyzed the data of 291 patients who underwent radical prostatectomy (RP) for a cT1-2N0 prostate cancer in a single surgeon series. All patients underwent preoperative staging with mpMRI. PIRADS v2 was used for characterizing lesions. The role of capsular abutment or bulging was tested in a multivariable logistic regression adjusting for prostate-specific antigen and highest ipsilateral biopsy Gleason grade. The presence of focal versus extensive extracapsular extension (ECE) was investigated. Results: Overall, ECE on final pathology was documented in 35 (12%) cases and ECE was focal in 32 (91%) patients. Overall, mpMRI demonstrated capsule bulging or abutment in 12 (24%) cases. After adjusting for confounders, capsule bulging or abutment on mpMRI emerged as predictor for ECE (OR=6.70; 95% CI: 2.97-15.12, P<0.001). The sensitivity and specificity of capsule abutment or bulging in predicting ECE were 43% and 95%, respectively. Sensitivity and specificity were 36% and 48% respectively to predict focal ECE. Conclusions: The PIRADS v2 scoring system has a grey zone concerning ECE as defined by capsule abutment or bulging. We found an increased risk of ECE and specifically focal ECE when capsule bulging or abutment on mpMRI are documented.