The role of staging MRI in predicting apical margin positivity for robot-assisted laparoscopic radical prostatectomy

To investigate the association between apical margin positivity and preoperative magnetic resonance imaging (MRI) in patients who have undergone robot-assisted laparoscopic radical prostatectomy (RARP).

From September 2010 through November 2012, we treated 84 Japanese men with clinically localized prostate cancer with RARP. The excised specimens, which were divided into right and left fragments, were evaluated for the presence of positive surgical margins (PSMs) and preoperative MRI findings.

The overall PSM rate was 21.4% (18 of 84 patients), 83.3% (15 of 18 cases) of which were situated in the apex. Evaluating the prostate divided into right and left fragments, the PSM rate was 10.7% at the apex (18 of 168 fragments). Cancer was suspected via preoperative MRI in 39 fragments (23.2%) and detected in the prostatic apex by prostate biopsy in 67 fragments (39.9%). Multiple regression analysis revealed that MRI and nerve-sparing procedures significantly indicate apical margin positivity (p = 0.005).

The prostatic apex is the most common location of PSMs after RARP. Our results demonstrate that preoperative MRI for cancer of the prostatic apex may provide substantial information and enable complete cancer clearance.