BACKGROUND: Multiparametric magnetic resonance imaging (MRI) combined with prostate-specific-antigen density (PSAd) enhances the detection of significant prostate cancer (sPCa). However, it is unclear whether simple biparametric (bp) MRI, which reduces scan sequences, time, and cost, may be an equally effective noninvasive tool for detecting and ruling out sPCa and avoiding biopsies in biopsy-naïve men.

OBJECTIVE: To assess the diagnostic accuracy, predictive values, and best biopsy strategy combining bpMRI and PSAd in detecting and ruling out sPCa (Gleason score ≥7).

DESIGN, SETTING, AND PARTICIPANTS: Assessment of 808 biopsy-naïve men with clinical suspicion of localised PCa (prostate-specific antigen <20ng/ml, rectal examination <cT3), prospectively enrolled between November 2015 and June 2017.

INTERVENTION: All men underwent upfront bpMRI (T2- and diffusion-weighted imaging) followed by standard and targeted biopsies of any suspicious bpMRI findings.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Various bpMRI scores and PSAd thresholds were assessed using sPCa detection rates, predictive values, and proportion of biopsies avoided. Net benefits and decision curve analyses were compared. Combined biopsies from all men were used for reference.

RESULTS AND LIMITATIONS: Significant prostate cancers were detected in 283/808 (35%) men with median age and PSA (interquartile range) of 65 yr (60-70) and 6.9ng/ml (5.4-9.5), respectively. PSAd significantly influenced the predictive values of bpMRI in detecting and ruling out sPCa. The best strategy was restricting biopsies to men with highly suspicious bpMRI findings (score ≥4) or PSAd ≥0.15ng/ml/cc. This reduced the number of men requiring biopsies by 41% (329/808) and overdiagnosis of insignificant cancers by 45% (79/177), while missing only 5% (17/329) of men with sPCa. Study limitations included single-centre analysis and combined biopsies as the reference standard.

CONCLUSIONS: Combination of bpMRI with PSAd improves diagnostic accuracy and predictive values for sPCa detection in biopsy-naïve men. Restricting biopsies to men with highly suspicious bpMRI findings (score ≥4) or PSAd ≥0.15ng/ml/cc was the best biopsy strategy in our patient cohort, effectively balancing risks and benefits. Studies are needed to validate our findings in other patient populations.

PATIENT SUMMARY: This report shows that biopsy-naïve men with clinical suspicion of prostate cancer who have low- or equivocal-suspicion biparametric magnetic resonance imaging results and a low prostate-specific antigen density may not require immediate prostate biopsies.