Model-Based Prebiopsy Risk Estimation and Systematic Core Omission During Transrectal Rigid Magnetic Resonance Imaging–Ultrasound Fusion Biopsy

Abstract Purpose Whether systematic cores can be omitted once a multiparametric magnetic resonance imaging (mpMRI) target is sampled depends on biopsy technique, yet existing evidence pools routes and registration methods. We identified prebiopsy determinants of clinically significant prostate cancer (csPCa) and quantified the cost of omitting systematic cores in a technically uniform cohort. Methods In this retrospective dual-centre study, 902 men with ≥ 1 Prostate Imaging Reporting and Data System (PI-RADS) ≥ 3 lesion underwent same-session targeted (TBx) and systematic biopsy transrectally with rigid software coregistration. Multivariable logistic regression identified factors associated with csPCa (International Society of Urological Pathology [ISUP] grade group ≥ 2) and high-grade cancer (hgPCa, ISUP ≥ 3), with Harrell's c-index, bootstrap validation, calibration and decision-curve analysis. TBx performance against overall biopsy was expressed absolutely, all biopsied men, and conditionally, men with csPCa. Results csPCa was detected in 338/902 men (37%), hgPCa in 91 (10%). Age, PSA density (PSAD), digital rectal examination (DRE) stage and maximum PI-RADS independently predicted csPCa; the optimism-corrected c-index was 0.80, exceeding each variable alone (0.70–0.74), with net benefit across 5–85% thresholds. For hgPCa, only PSAD and DRE remained independent. TBx sensitivity was 76% (71–81): the absolute miss rate, csPCa found only by systematic cores, was 8.9% (80/902), corresponding to a conditional rate of 24% (19–29), highest in PI-RADS 3 (35%) and at PSAD < 0.10 ng/ml/cm³ (43%). Conclusion Under transrectal rigid fusion, systematic cores should be retained. Imaging category alone does not identify high-grade disease; reduced sampling should be judged on the absolute rather than the conditional miss rate.