Case-by-case combination of the prostate imaging reporting and data system version 2.1 with the Likert score to reduce the false-positives of prostate MRI: a proof-of-concept study

Abstract

Objectives: To retrospectively investigate whether a case-by-case combination of the Prostate Imaging Reporting and Data System version 2.1 (PI-RADS) with the Likert score improves the diagnostic performance of mpMRI for clinically significant prostate cancer (csPCa), especially by reducing false-positives.

Methods: One hundred men received mpMRI between January 2020 and April 2021, followed by prostate biopsy. Reader 1 (R1) and reader 2 (R2) (experience of > 3000 and < 200 mpMRI readings) independently reviewed mpMRIs with the PI-RADS version 2.1. After unveiling clinical information, they were free to add (or not) a Likert score to upgrade or downgrade or reinforce the level of suspicion of the PI-RADS category attributed to the index lesion or, rather, identify a new index lesion. We calculated sensitivity, specificity, and predictive values of R1/R2 in detecting csPCa when biopsying PI-RADS ≥ 3 index-lesions (strategy 1) versus PI-RADS ≥ 3 or Likert ≥ 3 index-lesions (strategy 2), with decision curve analysis to assess the net benefit. In strategy 2, the Likert score was considered dominant in determining biopsy decisions.

Results: csPCa prevalence was 38%. R1/R2 used combined PI-RADS and Likert categorization in 28%/18% of examinations relying mainly on clinical features such as prostate specific antigen level and digital rectal examination than imaging findings. The specificity/positive predictive values were 66.1/63.1% for R1 (95%CI 52.9-77.6/54.5-70.9) and 50.0/51.6% (95%CI 37.0-63.0/35.5-72.4%) for R2 in the case of PI-RADS-based readings, and 74.2/69.2% for R1 (95%CI 61.5-84.5/59.4-77.5%) and 56.6/54.2% (95%CI 43.3-69.0/37.1-76.6%) for R2 in the case of combined PI-RADS/Likert readings. Sensitivity/negative predictive values were unaffected. Strategy 2 achieved greater net benefit as a trigger of biopsy for R1 only.

Conclusion: Case-by-case combination of the PI-RADS version 2.1 with Likert score translated into a mild but measurable impact in reducing the false-positives of PI-RADS categorization, though greater net benefit in reducing unnecessary biopsies was found in the experienced reader only.

Keywords: Biopsy; Multiparametric magnetic resonance imaging; PI-RADS; Prostatic neoplasms.

Fig. 1

Study flowchart. BCG = bacillus Calmette-Guérin; mpMRI = multiparametric magnetic resonance imaging; TURP = transurethral resection of the prostate

Fig. 2

Distribution of cases in which reader 1 (a) and reader 2 (b) used the Likert score to complement the PI-RADS categorization of index lesions. FN = false-negative; FP = false-positive; PI-RADS = Prostate Imaging Reporting and data System version 2.1; TN = true negative; TP = true-positive

Fig. 3

Case of Likert scoring by reader 1 reinforcing the level of suspicion of PI-RADS categorization in a 53-year-old man with a prostate-specific antigen level density of 0.08 ng/mL/mL and negative digital rectal examination. The index lesion in the right anterior peripheral zone of the midgland showed wedge-shaped mild hypointensity on the apparent diffusion coefficient map (arrow in a) and wedge-shaped mild hyperintensity on b = 2000s/mm² image (b), slight hypointensity on T2-weighted imaging (arrow in c) and early focal enhancement after contrast administration (arrow in d). The lesion was assessed as PI-RADS 2 and Likert 2. Transperineal systematic biopsy cores in the same quadrant and adjacent quadrant showed gland atrophy/subatrophy and chronic prostatitis

Fig. 4

Case of Likert-induced downgranding of lesion suspicion by reader 1 in a 62-year-old man. A mildly-hypointense atypical nodule in the left anterior transition zone of the midgland (arrow in a and b) showed restricted diffusion with marked hyperintensity on b = 2000s/mm² image (c) and marked hypointensity on the apparent diffusion coefficient map (d), and was categorized as a PI-RADS 2 upgraded to 3. Based on prostate-specific antigen level density of 0.07 ng/mL/mL and negative digital rectal examination, reader 1 downgraded the level of suspicion to Likert 2. A targeted prostate biopsy showed chronic prostatitis

Fig. 5

Decision curve analysis for reader 1 (a) and reader 2 (b) (see the main text for details)