Prostate magnetic resonance imaging and the value of experience:An intrareader variability study

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 mpMRIp scans using Prostate Imaging-Reporting and Data System version 2(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),positive predictive value(PPV),and accuracy were calculated,and comparison of sensitivity was performed using McNemar's test.Results Ninety-six mpMRIp scans were included in our final analysis.Of the 96 patients,53(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,re-reading demonstrated an increase in specificity(from 43%to 89%)and PPV(from 62%to 87%),but a decrease in sensitivity(from 94%to 72%,p=0.01)and NPV(from 89%to 77%).Conclusion The 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.