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 sometimes 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 cancer. 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 assessed time to PSA failure to determine the role of endorectal MRI in predicting PSA outcome after radical prostatectomy at our institution, where an expert 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 834 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 stratification of 5-year PSA outcome in the remaining 191 patients at intermediate risk based on established prognostic factors. Specifically when endorectal 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 72% (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 accounting for established prognostic factors. While further study of the value of this modality for predicting clinical outcome after radical prostatectomy should be performed in this select cohort, routine use of endorectal MRI cannot be justified based on these data.