Accuracy of endorectal Magnetic Resonance Imaging (MRI) and Dynamic Contrast Enhanced-MRI (DCE-MRI) in the preoperative local staging of prostate cancer: a prospective study in 46 patients.

Purpose: To assess the accuracy of endorectal MRI in association with DCE-MRI in the preoperative local staging of prostate cancer (PCa). Methods and Materials: After at least 6 weeks from biopsy, 46 consecutive patients with biopsy-proven PCa at intermediate/high-risk were prospectively evaluated with MRI, within 2 weeks before radical prostatectomy (RP). Assessment of radiological images and RP specimens were performed on 14 regions: 12 prostatic locations and 2 seminal vesicle locations. The likelihood of extracapsular extension (ECE) and seminal vesicle invasion (SVI) was scored on a 5-point scale in each region. We assessed sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy with ROC analysis of MRI, DCE-MRI and conventional staging methods using pathological findings as reference standard. Results: The mean values of age, PSA, prostate volume and pathological Gleason score were 65.7 years, 7.9 ng/ml, 65.7 ml and 7.45. At histopathology, 11/46 (24%) patients had pathological extraprostatic involvement: monolateral ECE (5), bilateral ECE (2), monolateral SVI (2) and bilateral SVI (2). Overall, 552 prostatic regions and 92 seminal vesicle regions were evaluated. The values of sensitivity, specificity, PPV, NPV and accuracy were: on a per-patient analysis, 81.8%, 91.4%, 75 %, 94.1%, 0.894; on a per-region analysis, 36.4%, 98.1%, 44.4%, 97.4%, 0.657. DCE-MRI did not improve the diagnostic accuracy of T2-weighted MRI in the evaluation of ECE/SVI. Conclusion: Endorectal-MRI adds important information regarding the preoperative local staging of PCa. However, the analysis region-by-region shows some limits of this imaging technique, in particular a low sensitivity, that must be considered before choosing a nerve-sparing approach.