Endorectal magnetic resonance imaging as a predictor of biochemical outcome after radical prostatectomy in men with clinically localized prostate cancer

Purpose: Endorectal magnetic resonance imaging (MRI) of the prostate is som etimes performed before radical prostatectomy but to our knowledge its role for predicting outcome after radical prostatectomy is not yet established. We evaluated the clinical usefulness of endorectal MRI for predicting time to prostate specific antigen (PSA) failure after radical prostatectomy in 1,025 consecutive men with clinically localized or PSA detected prostate ca ncer. Our analysis controlled for PSA level, biopsy Gleason score, clinical T stage and percent of positive biopsies. Materials and Methods: Using Cox regression analysis we prospectively asses sed time to PSA failure to determine the role of endorectal MRI in predicti ng PSA outcome after radical prostatectomy at our institution, where an exp ert prostate magnetic resonance radiologist is available. The main outcome measure was actuarial freedom from PSA failure. Results: Endorectal MRI did not add clinically meaningful information in 83 4 of our 1,025 cases (81%) after accounting for the prognostic value of PSA , biopsy Gleason score, clinical T stage and percent of positive biopsies. However, this modality provided a clinically and statistically relevant str atification of 5-year PSA outcome in the remaining 191 patients at intermed iate risk, based on established prognostic factors. Specifically when endor ectal MRI was interpreted as indicating extracapsular versus organ confined disease the relative risk of PSA failure was 3.6 (95% confidence interval 2.0 to 6.3), and 5-year actuarial freedom from PSA failure was 33% versus 7 2% (p <0.0001). Conclusions: Despite expert radiological interpretation endorectal MRI had potential clinical value in less than 20% of the cases in our study after a ccounting for established prognostic factors. While further study of the va lue of this modality for predicting clinical outcome after radical prostate ctomy should be performed in this select cohort, routine use of endorectal MRI cannot be justified based on these data.