MRI should be routine for all patients with localized prostate cancer? | Opinion: Yes

Magnetic resonance imaging (MRI) has been used for staging prostate cancer (PCa) since the 1990’s, more precisely after the advent of the endorectal coil, which enabled significant improvement in the quality of the examination. Also, the standardization of prostate MRI with multiparametric sequences (including high resolution T2-weighted, diffusion and dynamic contrast-enhanced or perfusion images), together with the progressive learning curve by uro-radiologists, contributed to include the method definitively in the list of available procedures for staging prostate cancer (1). The accuracy of multiparametric MRI (mpMRI) is greater than that of other isolated clinical, laboratory and imaging methods available, with specificities around 85% for detection of extracapsular extension and seminal vesicle invasion (2). Moreover, the incremental value of MRI has been validated around a decade ago in three articles by the interdisciplinary group of Memorial Sloan Kettering Cancer Center, demonstrating that the addition of MRI to the commonly used clinical nomograms significantly increases the accuracy for prediction of organ-confined disease, extracapsular extension and seminal vesicle invasion (3-5). The indication and acceptance of mpMRI for prostate cancer staging increased after the development and clinical use of 3 Tesla (T) scanners (which have twice the magnet field strength in comparison to more common 1.5 T scanners), allowing the achievement of multiparametric studies of the prostate without the need for an endorectal coil, with the same resolution and image quality as compared to the studies on 1.5 T scanners with endorectal coil (6). On the other hand, performing mpMRI for staging of PCa after the biopsy has some limitations. First, a recent meta-analysis with a very large number of studies and patients, evaluating the performance of MRI for local staging of disease, showed high specificities (88-96%) but low sensitivities (57-61%), considering that microscopic infiltration of the capsule or seminal vesicles might be undetectable even with state-of-the-art equipments and protocols (7). Also, there must be a minimum interval of three weeks between prostate biopsy and MRI, to minimize bleeding artifacts that impair the interpretation of the study (8). Finally, it is arguable that very-low and low risk tumors would not benefit from a staging mpMRI, since the chance of extraprostatic disease is small (9). In this decade, a new and promising application for MRI has emerged: by using standardized interpretation and reporting systems (like PI-RADS and Likert), mpMRI can be used as an additional screening tool to stratify the risk for prostate cancer. mpMRI has the ability DIffERENCE Of OPINION