Testing PI-RADS Accuracy

By: Dan Sperling, MD

I recently posted a blog describing PI-RADS (Prostate Imaging Reporting and Data System) which is a means of standardizing prostate MRI interpretation. I found a very encouraging study[i] that evaluates how well this scoring system stands up to actual prostate biopsies, especially when compared to an earlier scoring system called the Likert score.

The study was conducted by German researchers in the Division of Radiology at the German Cancer Research Center in Heidelberg. Lead author Matthias Roethke is widely published, especially in prostate MRI, and he heads a very credible team.

The study involved 64 patients who underwent 3T multiparametric MRI prior to having MR/TRUS fusion guided biopsies. Any suspicious lesions identified by mpMRI were then scored using the PI-RADS classification, which assigns a value of 1-5 (from probably benign (1) to probably malignant (5) for each imaging parameter (see my previous blog, ). The chart below shows the classification when the values are totaled:

PI-RADS Classification System

PI-RADS classification

Definition

Total T2, DWI, DCE

Total T2, DWI, DCE, MRS

I

Most probably benign

3, 4

4, 5

II

Probably benign

5, 6

6-8

III

Indeterminate

7-9

9-12

IV

Probably malignant

10-12

13-16

V

Most probably malignant

13-15

17-20

The images were also scored using a simple Likert scoring system (1-5) which lacks the fine-tune analysis that PI-RADS affords. On the imaging, a total of 95 “regions of interest” were identified. Under fusion guidance, a total of 445 biopsy needles were taken from the regions of interest, averaging less than 5 cores per patient. 128 of the biopsy samples proved positive for prostate cancer. Thus, 27 out of the 64 patients had biopsy-proven prostate cancer. The biopsy results were compared with the PI-RADS system and the Likert scores for the regions of interest.

The authors found that PI-RADS was superior in both sensitivity and specificity. I am not surprised, because PI-RADS is based on at least three parameters (T2, DWI, and DEC) that highlight different tumor characteristics. The article concludes, “The standardized ESUR PI-RADS system if beneficial to indicate the likelihood of PCa of suspicious lesions on mpMRI. It is also valuable to identify locations to be targeted with biopsy. The aggregated PI-RADS score achieved better results compared to the single five-point Likert score.”

3T mpMRI offers us an image-rich portrait of prostate tumors that no other imaging can compare with. Experienced readers who knowledgeably assign PI-RADS scores to each parameter that shows a suspicious area are doing a great service for patients. At our center, we are fortunate indeed to contribute such detection and diagnosis methods for our patients.

 


[i] Roethke MC, Kuru TH, SchultzeS, et al. Evaluation of the ESUR PI-RADS scoring system for multiparametric MRI of the prostate with targeted MRI-TRUS fusion-guided biopsy at 3.0 Tesla. Eur Radiol. 2014;24(2):344-352.