Reconciling discordance between PI-RADS 4 lesions and targeted biopsy: Early experience of a multidisciplinary quality improvement protocol with PI-RADS 4 subcategorization

PI-RADS 4 lesions are considered to have a "high" likelihood of clinically-significant prostate cancer (csPCa). However, patients undergoing targeted biopsy have a range of histologic findings. Understanding discordant cases is critical to improve diagnostic accuracy and inform subsequent management. We studied early findings from implementation of a multidisciplinary Quality Improvement (QI) protocol for reconciling discordance and evaluate the potential heterogeneity of PI-RADS 4.Patients with mpMRI PI-RADS 4 lesions undergoing fusion-targeted biopsy from January 2017 to May 2021 were retrospectively reviewed. The discordant targeted biopsy pathology (benign/GG1) was evaluated utilizing a QI protocol and all lesions were subcategorized based on ADC values. Positive Predictive Value (PPV) for PI-RADS 4 lesions overall and the Cancer Detection Rate (CDR) for subcategorized lesions were calculated.248 patients with 286 lesions were reviewed. Prior to re-review, PI-RADS 4 PPV for ≥ GG1 and ≥ GG2 lesions were 0.55 and 0.34, increasing to 0.67 and 0.43 following reconciliation. Lesion subcategorization based on ADC value as higher suspicion (4+) and lower suspicion (4-) resulted in 158 and 117 lesions, with reverse-fusion analysis revealing that 61% and 17% of lesions contained csPCa, respectively. Subgroup analysis among PI-RADS 4+ lesions led to an increase in the CDR to 75% and 61% for ≥ GG1 and ≥ GG2.Use of multidisciplinary QI protocol to review discordance cases of PI-RADS 4 improves diagnostic accuracy and guides subsequent management. Our findings highlight the known heterogeneity of this category with reference to csPCa CDR, suggesting the potential value of PI-RADS 4 subcategorization.