Introducing PI-RADS version 2: application of multiparametric MRI scans for prostate cancer risk assessment

PI-RADS™ stands for Prostate Imaging and Reporting and Data System and is a system used to guide standardization and limit variation in the performance, interpretation, and reporting of prostate MRI exams prior to any form of active treatment. The initial version of this system was introduced in 2012 (see here for an earlier discussion).

Very recently the American College of Radiology (ACR), in conjunction with the European Society of Urogenital Radiology (ESUR) and the AdMeTech Foundation — through a joint PI‐RADS Steering Committee — has formally introduced an updated version of the PI-RADS system (PI-RADS version 2) which will now be considered to be set the new, approved standards for the performance, interpretation, and evaluation of prostate MRI exams used in the initial diagnosis of prostate cancer. (Note, however, that the PI-RADS systems do not encompass the use of MRI scanning in the later evaluation of patients with prostate cancer after any form of actual treatment.)

There are a number of documents related to the use of PI-RADS v2 that may be of interest to some readers, particularly support groups leaders and other prostate cancer educators. These include some or all of the following:

From a patient perspective there are also changes in the way in which particular PI-RADS values should be interpreted compared to the older version. Using the new PI-RADS v2 system, assessment of multiparametric MRIs should be reported as PI-RADS scores of 1 to 5 with the following implications:

The PI-RADS v2 assessment categories are defined with the following scores:

  • PI-RADS score 1: Very low risk, implying that clinically significant prostate cancer is highly unlikely to be present
  • PI-RADS score 2: Low risk, implying that clinically significant prostate cancer is unlikely to be present
  • PI-RADS score 3: Intermediate risk, implying that the presence of clinically significant disease is equivocal
  • PI-RADS score 4: High risk, implying that clinically significant prostate cancer is likely to be present
  • PI-RADS score 5: Very high, implying that clinically significant prostate cancer is highly likely to be present

We would re-emphasize that patients should understand that:

PI-RADS v2 is not intended to be a comprehensive [prostate cancer] diagnosis manual; it should be used in conjunction with other resources. Its intended clinical application is for the diagnostic evaluation and risk assessment of patients with suspected [prostate cancer] prior to or after transrectal ultrasound (TRUS) biopsy. It has not been developed for detecting suspected recurrent [prostate cancer] following therapy.

From a practical point of view, this means that PI-RADS v2 can and should be applied in the MRI evaluations of patients at time of initial diagnosis and/or in the repetitive MRI evaluations of patients on active surveillance. It is not appropriate to use this system in the evaluation of MRI data of any patient who has received invasive or systemic treatment.

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