Impact of preoperative endorectal MRI stage classification on neurovascular bundle sparing aggressiveness and the radical prostatectomy positive margin rate.

INTRODUCTION: Inability to accurately determine extracapsular extension (ECE) and neurovascular bundle (NVB) tumor involvement prior to or during radical prostatectomy (RP) remains problematic. Laparoscopic prostatectomy has the additional challenge of lack of tactile tumor assessment. Our goal is to determine the impact of preoperative endorectal magnetic resonance imaging (eMRI) staging upon NVB sparing aggressiveness and the RP surgical margin rate.
METHODS: Sixty-two patients who underwent RP (46 laparoscopic and 16 open retropubic) from March 2002 to February 2005 and had preoperative eMRI staging were evaluated to determine the impact of apparent ECE upon NVB sparing aggressiveness and subsequent RP margin positivity.
RESULTS: Thirty-four (83%) of 41 pathologic stage T2 tumors and 8 (38%) of 21 pathologic stage T3 tumors were accurately classified by eMRI. Eighty-three percent of eMRI stage T2 classified tumors underwent bilateral NVB sparing, whereas only 55% of laparoscopic (P = 0.09) and 75% of open RP (P = 1.0) tumors classified as eMRI stage T3 underwent bilateral NVB sparing. The overall surgical margin positive rate was 30% for laparoscopic and 25% for open RPs. Pathologic T3 tumors erroneously classified as T2 demonstrated a trend towards greater positive margin rate (54% vs. 13% [P = 0.07], 63% vs. 14% laparoscopic RP [P = 0.12]). Eighty percent of clinical T1c, Gleason score 6, pathologic T3 tumors classified erroneously as T2 by eMRI had positive margins.
CONCLUSIONS: The usefulness of endorectal MRI in detecting ECE is limited. Patients with eMRIs suggesting no ECE demonstrated a trend towards more aggressive NVB sparing and an increased positive surgical margin rate at laparoscopic prostatectomy.