Extraprostatic Tumor Extension: Comparison of Preoperative Multiparametric MRI Criteria and Histopathologic Correlation after Radical Prostatectomy

Background: There are no standardized and well-validated criteria for assessing the risk of extraprostatic extension (EPE) of prostate cancer at preoperative multiparametric MRI. Purpose: To compare diagnostic performance, intra- and interreader agreement, and correlations of MRI-based criteria for assessment of EPE after radical prostatectomy, including EPE grade, European Society of Urogenital Radiology (ESUR) score, Likert scale, and capsular contact length (CCL). Materials and Methods: This retrospective study included consecutive men who underwent MRI and radical prostatectomy between July 2016 and March 2017. Two genitourinary radiologists independently estimated the probability of EPE by using four MRI-based scoring methods. The diagnostic accuracies and intra- and interobserver agreement were evaluated with area under the receiver operating characteristic curve (AUC) and k statistics, respectively. Correlations between MRI-based score and histologic extent of EPE were analyzed by using the Spearman correlation coefficient (rho). Results: A total of 301 men (mean age +/- standard deviation, 65 years +/- 7) were evaluated. A total of 129 (42.9%) men had EPE. The AUC ranges of EPE grade, ESUR score, Likert scale, and CCL for assessment of EPE were 0.77-0.81, 0.79-0.81, 0.78-0.79, and 0.78-0.85, respectively, for the two readers. The Likert scale showed lower sensitivity (68.2% [88 of 129] for reader 1, 72.1%[93 of 129] for reader 2) than did EPE grade (77.5% [100 of 129] for reader 1, 79.8% [103 of 129] for reader 2; P <= .04). Intra-and interreader agreement were substantial (kappa range, 0.61-0.74) for the four methods, with ESUR score showing the lowest values(kappa = 0.61 and kappa = 0.63, respectively). EPE grade showed highest correlation with histologic extent of EPE (rho = 0.53 and rho = 0.55 for circumferential length; rho = 0.42 and rho = 0.55 for radial length for readers 1 and 2, respectively; P < .001). Conclusion: Extraprostatic extension (EPE) grade, European Society of Urogenital Radiology score, Likert scale, and capsular contact length showed good overall diagnostic performance; however, the EPE grade resulted in more reliable performance and had the highest correlation with histologic EPE extent. (C) RSNA, 2020