PI-RADS is an acronym for Prostate Imaging Reporting and Data System, defining standards of high quality clinical service for multi-parametric Magnetic Resonance Imaging (mpMRI), including image creation and reporting.
Contents
History
Since 2007, the AdMeTech Foundation's International Prostate MRI Working Group convened the key global experts, including members of the American College of Radiology (ACR) and European Society of Urogenital Radiology (ESUR). They reviewed emerging scientific evidence, developed research strategy and by early 2010, recommended development of the PI-RADS standardization, modeled after BI-RADS for Breast Imaging-Reporting and Data System, a quality assurance tool in breast imaging ,. The goal of this recommendation was to expedite large-scale clinical evaluation and implementation of high quality mpMRI for improved early detection and accurate diagnosis of clinically significant prostate cancer.
In response to this recommendation, ESUR developed PI-RADS version 1 (PI-RADS v1). Upon review of PI-RADS v1 in early 2011, AdMeTech Foundation's International Prostate MRI Working Group initiated development of global consensus for PI-RADS standardization (PI-RADS v2) and stimulated the interest of ACR and ESUR to ensure global acceptance and implementation. In late 2011, AdMeTech Foundation, ACR and ESUR formed a Joint Steering Committee, and by December 2014, developed and released an online version of PI-RADS v2, With support of the AdMeTech Foundation and ESUR, ACR trademarked the PI-RADS v2 version in order to provide leadership in education and training. In 2015, a scholarly article on PI-RADS v2 was accepted for publication in the Journal of European Urology; it was accompanied by the editorial detailing extensive differences between PI-RADS v1 and PI-RADS v2.
Since 2011, AdMeTech Foundation has also taken the lead in designing and managing a clinical trial, in partnership with the American College of Radiology Imaging Network, with the goal to provide a definitive scientific evidence on the value of mpMRI and PI-RADS v2 in addressing the central challenges in patient care: 1) Improving early detection of clinically significant prostate cancer, as defined by Gleason Grade 4 and higher and informed by volume of > 0.5 cc of the index lesion (which is considered the most clinically relevant); and 2) Reducing over-diagnosis and over-treatment of benign diseases and dormant cancer, which are not likely to cause harm in a man's lifetime. The first phase of this trial, which was undertaken by AdMeTech jointly with scientists of the Harvard Medical School (Brigham and Women's Hospital, Dana Farber Cancer Institute and the Massachusetts General Hospital), is expected to be completed in June 2016. If successful, this trial will expedite global clinical implementation of mpMRI and PI-RADS v2.
Purpose
The PI-RADS v2 system is designed to standardize image acquisition and reporting, and to be used by medical professionals in the initial evaluation of patients to assess the risk of clinically significant prostate cancer that may require biopsy and treatment. The online document and the related publications in the Journal of European Urology, which represent an international scientific consensus, are written for medical professionals, not "lay" patients or members of the general public.
PI-RADS score
A PI-RADS v2 score is given according to each variable parameter. The scale is based on a score "Yes" or "No" for Dynamic Contrast-Enhanced (DCE) parameter, and from 1 to 5 for T2-weighted (T2W) and Diffusion-weighted imaging (DWI). The score is given for each lesion, with 1 being most probably benign and 5 being highly suspicious of malignancy:
PI-RADS Performance
Various studies have compared the predictive performance of PI-RADS v1 for detecting significant prostate cancer against either image-guided biopsy results (definitive pathology) and/or prostatectomy specimens (histopathology). In a 2015 articles in the Journal of Urology, Thompson reported multiparametric MRI detection of significant prostate cancer had sensitivity of 96%, specificity of 36%, negative predictive value and positive predictive values of 92% and 52%; when PI-RADS was incorporated into a multivariate analysis (PSA, digital rectal exam, prostate volume, patient age) the area under the curve (AUC) improved from 0.776 to 0.879, p<0.001. A similar paper in European Radiology found that when correlated with histopathology, PI-RADS v2 correctly identified 94-95% of prostate cancer foci ≥0.5 mL, but was limited for the assessment of GS ≥4+3 (significant) tumors ≤0.5 mL; in their series, DCE-MRI offered limited added value to T2WI+DW-MRI. Other applications for which PI-RADS may be useful include prediction of termination of Active Surveillance due to tumor progression/aggressiveness, detection of extraprostatic extension of prostate cancer, and supplemental information when considering whether to re-biopsy patients with a history of previous negative biopsy.
PI-RADS v2 is designed to improve detection, characterization and risk stratification in patients suspected of prostate cancer with a goal of better treatment decisions, improved outcomes and simplified reporting. However, multi-center validation trials are needed and expected to lead to modifications in the scoring system.