Avoiding Unnecessary Magnetic Resonance Imaging (MRI) and Biopsies: Negative and Positive Predictive Value of MRI According to Prostate-specific Antigen Density, 4Kscore and Risk Calculators

The 2019 European Association of Urology guidelines recommend multiparametric magnetic resonance imaging (mpMRI) for biopsy-naïve patients with clinical suspicion of prostate cancer (PC) and avoiding biopsy in patients with negative mpMRI and low clinical suspicion. However, consensus on the optimal definition of low clinical suspicion is lacking. We evaluated 266 biopsy-naïve patients who underwent mpMRI, the 4Kscore test, and prostate biopsy to define the best strategy to avoid unnecessary testing and biopsies. The European Randomized Study of Screening for Prostate Cancer risk calculator (ERSPC-RC) and prostate-specific antigen density (PSAd) were also considered. For men with Prostate Imaging-Reporting and Data System v2.0 (PI-RADS) 1⿿2 lesions, the highest negative predictive value was observed for those with low or intermediate 4Kscore risk (96.9% and 97.1%), PSAd <0.10ng/ml/cm3 (98.7%), and ERSPC-RC <2% (98.7%). For men with PI-RADS 3⿿5 lesions the lowest positive predictive value was observed for those with low 4Kscore risk (0%), PSAd <0.10ng/ml/cm3 (13.2%), and ERSPC-RC <2% (12.3%). The best biopsy strategy was an initial 4Kscore followed by mpMRI if the 4Kscore was>7.5% and a subsequent biopsy if the mpMRI was positive (PI-RADS 3⿿5) or the 4Kscore was ⿥18%. This would result in missing 2.7% (2/74) of clinically significant PCs (csPCs) and avoiding 34.2% of biopsies. Initial mpMRI followed by biopsy for negative mpMRI (PI-RADS 1⿿2) if the 4Kscore was ⿥18% or PSAd was ⿥0.10ng/ml/cm3 resulted in a similar percentage of csPC missed (2.7% [2/74] and 1.3% [1/74]) but slightly fewer biopsies avoided (25.2% and 28.1%). Physicians should consider clinical risk screening tools when ordering and interpreting mpMRI results to avoid unnecessary testing and diagnostic errors.