Background: Endorectal MRI of the prostate is being widely used as a preoperative staging tool in patients with prostate cancer. After much initial enthusiasm, the accuracy of this staging tool is now being questioned. We now present our institutional data with endorectal MRI to determine the usefulness of this imaging modality.
Methods: This is a retrospective review of 51 patients with prostate cancer who underwent preoperative endorectal MRI and radical prostatectomy between March 2002 and March 2005. Patient characteristics, preoperative MRI data, preoperative prostate biopsy pathology, and surgical specimen pathology were examined.
Results: The 51 patients had a mean age of 60 + 6 years, a mean preoperative PSA of 7.86 + 5.56 ng/ml, and a mean biopsy Gleason score of 7 + 0.8. Sixteen (31%) patients underwent open radical retropubic prostatectomy while 35 (69%) underwent laparoscopic radical prostatectomy. Thirty-four (67%) were pT2 and 17 (33%) were pT3. Two patients (4%) had pT3c disease. Thirty-eight (75%) underwent bilateral pelvic lymph node dissection at the time of the prostatectomy. Endorectal MRI had a sensitivity of 20%, specificity of 90%, positive predictive value of 33%, and negative predictive value of 82% for detecting extracapsular extension. When subdivided, patients with a biopsy Gleason score of 6 and 7 (n=40) had a sensitivity of 8%, specificity of 93%, positive predictive value of 17%, and negative predictive value of 84%. The Gleason 8 and 9 patients (n=10) had a sensitivity of 33%, specificity of 79%, positive predictive value of 40% and negative predictive value of 73%. As for seminal vesicle invasion, endorectal MRI had a sensitivity of 33%, specificity of 97%, positive predictive value of 25%, and negative predictive value of 98%.
Conclusions: Endorectal MRI has low sensitivity and positive predictive value for extracapsular extension and seminal vesicle involvement. However, the specificity and negative predictive value are quite good. This aspect of endorectal MRI may be beneficial when applied toward evaluating a patient who is at high risk for extracapsular extension and seminal vesicle involvement. The high specificity and negative predictive value of this tool may influence the urologist to consider surgical therapy in these patients who otherwise may have been pushed toward other treatment modalities.

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