Prostate MRI and the value of experience: An intrareader variability study

Abstract Objective To measure the intraobserver concordance of an experienced genitourinary radiologist reporting of multiparametric magnetic resonance imaging of the prostate (mpMRIp) scans over time. Methods An experienced genitourinary radiologist re-reported his original 100 consecutive 3T mpMRIp scans using PI-RADS v2. after 5 years of further experience comprising >1000 scans. Intraobserver agreement was measured using Cohen's kappa. Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were calculated, and comparison of sensitivity was performed using McNemar's test. Results Ninety-six mpMRIp scans in our final analysis. Fifty-three (55.2%) patients underwent subsequent biopsy (n = 43) or prostatectomy (n = 15), with 73 lesions targeted. Moderate agreement (Cohen's kappa 0.55) was seen in the number of lesions identified at initial reporting and on re-reading (81 vs. 39 total lesions; and 71 vs. 37 number of PI-RADS ≥3 lesions). For clinically significant prostate cancer (csPCa), re-reading demonstrated an increase in specificity (43%–89%) and PPV (62%–87%), but a decrease in sensitivity (94%–72%, p = 0.01) and NPV (89%–77%). Conclusions Intraobserver agreement for a novice to experienced radiologist reporting mpMRIp using PI-RADS v2. Is moderate. Reduced sensitivity is off-set by improved specificity and PPV, which validate mpMRIp as a gold standard for prebiopsy screening.