Micro-ultrasound (microUS) guided prostate biopsy (MUB) has emerged as a non-inferior alternative to magnetic resonance imaging (MRI)-targeted biopsy (MTB) for detecting clinically significant prostate cancer (csPCa) (Gleason grade group >= 2). MicroUS is a novel three hundred times higher-resolution ultrasound technology that operates at 29 MHz, allowing for free hand transperineal prostate biopsies. Suspicious lesions are classified using the Prostate Risk Identification using MicroUS (PRI-MUS) system (score 1–5), which correlates closely with the Prostate Imaging Reporting and Data System (PI-RADS) classification. Compared to conventional methods, microUS offers a cost-effective and accurate biopsy platform, granting urologists greater procedural autonomy. Our primary aim is to evaluate the diagnostic performance of MUB in comparison to MTB for the detection of csPCa. Secondary aims include: (1) assessing microUS's capability to identify MRI-invisible lesions and (2) determining the differential accuracy between MTB and saturation biopsy (SB).

Biopsy-naïve men with clinical suspicion of prostate cancer were prospectively enrolled from January to March 2025 at Sengkang General Hospital. All patients had multiparametric MRI prior to biopsy. They underwent transperineal cognitive MUB by surgeon 1 (blinded to MRI, targeting PRI-MUS >=3) followed by transperineal MTB and SB using the Biobot MonaLisa system by surgeon 2 in the same setting (targeting PIRADS ≥ 3). The diagnostic performance of MUB and MTB in detecting csPCa was compared for non-inferiority with a difference of 10%. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of MUB was assessed with reference to MTB. The differential accuracy of MTB and SB was evaluated.

Our cohort comprised 21 predominantly Chinese (90.4%) men with mean age 66.1 years, median PSA 7.2 ng/mL, and median PSA density 0.18 ng/mL/cc. Most lesions were PIRADS 4-5 (76.7%) and PRI-MUS 4-5 (89.4%). MUB demonstrated higher detection rate of csPCa compared to MTB (42.9% versus 38.1%, respectively; absolute difference 4.8%), meeting non-inferiority criteria. Relative to MTB, MUB achieved 85.7% sensitivity, 85.7% specificity, 92.3% PPV, and 75% NPV. Notably, 33.3% of patients had MRI invisible lesions biopsied on MUB, of whom 85.7% were csPCa. However, MUB missed MRI-visible lesions in 9.5% of patients who had csPCa. Saturation biopsies identified csPCa in 38.1% of the cohort. Targeted biopsies had marginally better detection (differential accuracy: 9.5%) versus saturation biopsies, with exact agreement in 61.9% of the cases.

In this first study in Asian patients, MUB is non-inferior to MTB in detecting csPCa. In addition, MUB was able to detect clinically significantly MRI invisible lesions in 28.6% of patients. The marginal advantage of MTB over SB suggests both approaches provide complementary value. MicroUS is an accurate and safe alternative to conventional MTB.