Added value of systematic biopsy in patients with positive MRI-US fusion targeted biopsy for clinically significant prostate cancer: a single-center retrospective study

To evaluate the added value of systematic biopsy (SB) in patients with positive targeted biopsy (TB) in the context of transperineal MRI-US fusion prostate biopsy, specifically focusing on clinically significant prostate cancer (csPCa), and to identify characteristics of patients who may benefit from a TB-only strategy. We retrospectively enrolled 260 patients who underwent transperineal MRI-US fusion biopsy (4-core TB plus 12-core SB) at Nantong First People’s Hospital between May 2024 and November 2025. All patients had positive TB results for prostate cancer. SB zero-benefit for csPCa was defined as TB detecting csPCa (Grade Group ≥ 2) while SB detecting no csPCa (either negative or only Grade Group 1). Multivariate logistic regression was used to analyze predictors of SB zero-benefit. A predictive model was constructed and validated using Bootstrap (2000 resamples). Model performance was assessed using ROC curves, calibration plots, and decision curve analysis (DCA). Among 260 patients with TB-detected csPCa, 25 (9.6%) exhibited SB zero-benefit for csPCa. Compared with the SB-positive group (n = 235), the SB zero-benefit group exhibited significantly larger prostate volume, lower PSAD, smaller lesion size, and a distribution toward lower-risk PI-RADS scores. Multivariate analysis revealed that lesion size (OR = 0.802, 95%CI: 0.657–0.978, P = 0.030) and PI-RADS score (4 vs. 3: OR = 0.022, P < 0.001; 5 vs. 3: OR = 0.027, P = 0.013) were independent predictors of SB zero-benefit. The predictive model demonstrated excellent discrimination (AUC = 0.910, 95%CI: 0.851–0.968; bootstrap-corrected AUC = 0.892) with acceptable calibration (Hosmer-Lemeshow P = 0.503). At the optimal cutoff (predicted probability = 0.122), sensitivity of 84.0%, specificity of 87.2%, and negative predictive value (NPV) of 98.1%. If SB had been omitted, 25 patients (9.6%) with csPCa detected only by SB would have been missed, while TB alone detected 100% of csPCa in this cohort. DCA showed higher net benefit across threshold probabilities of 0.1–0.9 compared to the “biopsy-all” strategy. Approximately 10% of patients with TB-detected csPCa exhibited SB zero-benefit, characterized by small lesions (≤ 11 mm) and low PI-RADS scores (3–4). The predictive model based on lesion size and PI-RADS effectively identified patients with low SB value (NPV 98.1%) in this internal validation. However, given the single-center retrospective design, small event number (n = 25), lack of external validation, and the 9.6% miss rate if SB were omitted, this model requires prospective multicenter validation before clinical implementation. For patients at initial diagnosis, a transperineal TB-only strategy may warrant further prospective validation in selected patients with PI-RADS 3–4 lesions ≤ 11 mm, whereas PI-RADS 5 lesions should undergo combined biopsy given the risk of false-positive MRI findings and the need for maximal cancer characterization. Not applicable.