MRI Predicts Prostatic Urethral Involvement in Men Undergoing Radical Prostatectomy: Implications for Cryo-Ablation of Localized Prostate Cancer

In this collaborative study between the departments of Urology of NYU Langone Health and USC Keck School of Medicine, we sought to determine if multi-parametric MRI (mpMRI) is a useful tool to determine if foci of prostate cancer are approaching the urethra. This is relevant information not only for urologists performing whole gland cryoablation but also for any physician planning any urethral sparing treatment modality (such as SBRT, brachytherapy, or HIFU).

The concept of this study was to retrospectively analyze our whole-mount radical prostatectomy (RP) specimens and stratify them according to the length of the index tumor to the prostatic urethra. Since it has been the protocol of both institutions for many years now to request a mpMRI before any RP, our radiologists re-read those scans and did a similar exercise. We measured the distance from the index MRI lesion to the urethra while being blinded from the pathology findings. We then calculated the performance of the MRI to predict if the index tumor was closer than 5mm to the urethral lumen.

We found that mpMRI has a moderate performance in prediction, but a high positive predictive value, so if the mpMRI finds that the index lesion is in close proximity to the urethra, then that patient may not be an optimum candidate for a urethral sparing procedure. We also found that 70% of patients undergoing RP have tumors close to the urethra, and also that these tumors present a higher Gleason group and other high-risk features. The findings of this study, however, cannot be extrapolated to candidates for focal therapy, as the cohort was comprised of candidates for RP. Future studies may look towards generalizing these findings and looking if they apply to a focal therapy candidate cohort.

Written by: Ezequiel Becher, MD, Department of Urology, NYU Langone Health, New York, NY

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