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Introduction
MRI is used for staging prior to RP, and has modest sensitivity for detection of ECE. To see how MRI influences surgical practice, we assessed positive surgical margin (PSM) and nerve-sparing (NS) rates in patients undergoing MRI prior to RP, compared to controls.
Methods
We identified 180 patients that received prostate MRI within 60d of RP at our institution between 2008-2013, and compared them to a non-MRI-scanned control-group matched by age, PSA, Gleason score, race, BMI, prostate size, and surgery year.
Results
PSM rate was 14% in the MRI group, compared to 17% in controls (p=0.54). ECE rates (21%) were similar. Within the MRI group, 40 (22%) patients had MRIs suspicious for ECE (93% unilateral); 23% of those had a PSM, 67% of which were at the same location as the MRI abnormality. Of the 140 without ECE on MRI, 11% had a PSM. For ECE detection, MRI had a sensitivity=45%, specificity=83%, PPV=41%, and NPV=83%. NS rates were similar, 93% (MRI group) and 95% (control; p=0.13). Patients with ECE on MRI had lower rates of NS, 82% vs. 95% (p=0.01).
Conclusions
PSM rates are higher when ECE is suspected on MRI, often occurring at the area of MRI abnormality, suggesting that these patients may benefit from even wider resections. Rates of NS were nevertheless high and PSM were low in this contemporary cohort, as ECE noted on MRI is most often unilateral and allows for more aggressive resection on the involved side and judicious NS on the contralateral side.