Prostate cancer: detection of extracapsular extension by genitourinary and general body radiologists at MR imaging

Abstract

Purpose: To determine whether predictive value of endorectal magnetic resonance (MR) imaging findings in detection of prostate cancer extracapsular extension (ECE) is significantly affected by the reader's subspecialty experience.

Materials and methods: In this cohort study, 344 consecutive patients with biopsy-proved prostate cancer underwent endorectal MR imaging followed by surgery. Likelihood of ECE described in MR imaging reports was compared with clinical predictor variables. ECE was determined from the final pathologic report on specimens resected at surgery. Readers of MR images were classified into genitourinary MR imaging radiologists (n = 4) and general body MR imaging radiologists (n = 6). For data analysis, Wilcoxon rank sum and chi(2) tests, as well as receiver operating characteristic (ROC) curves and univariate and multivariate logistic regression analyses, were used. A difference with P <.05 was considered significant.

Results: Univariate analysis results demonstrated that all predictors except clinical stage were significantly associated with detection of ECE in both groups of readers (P <.05). In the genitourinary MR imaging radiologist group of patients, area under the ROC curve for endorectal MR imaging findings (0.833) was larger than areas under the curves for all other predictors (0.566-0.701). In the general body MR imaging radiologist group of patients, area under the ROC curve for endorectal MR imaging findings (0.646) was not larger than areas under the curves for all other predictors (0.582-0.793). Results of multivariate analysis of two models, one with all predictors and another with all predictors except endorectal MR imaging findings, demonstrated a significant increase in area under the ROC curve with endorectal MR images interpreted by genitourinary MR imaging radiologists (P =.019 and.31, respectively).

Conclusion: Endorectal MR imaging findings are significant predictors for detection of ECE when MR images are interpreted by genitourinary radiologists experienced with MR imaging of the prostate.