Incremental detection of clinically significant prostate cancer by systematic biopsy outside MRI-targeted lesions during cognitive fusion local anaesthetic transperineal biopsy.

OBJECTIVE: To evaluate the incremental yield of clinically significant prostate cancer (csPCa) detected by systematic biopsy outside MRI-targeted lesions during cognitive fusion local anaesthetic transperineal prostate biopsy. PATIENTS AND METHODS: This observational cohort study included men undergoing cognitive MRI-targeted prostate biopsy with concurrent systematic sampling. Pre-biopsy MRI findings were recorded using PI-RADS. The primary outcome was csPCa detected exclusively by systematic biopsy outside MRI-targeted lesions despite a negative targeted biopsy. Secondary outcomes included csPCa detection by targeted, systematic, and combined biopsy, PI-RADS subgroup analysis, and multivariable predictors of csPCa. RESULTS: Overall, 770 men were included, of whom 767 had evaluable paired biopsy data. Most had PI-RADS 4 lesions (636/767, 82.9%). csPCa was detected by targeted biopsy in 320/767 men (41.7%), systematic biopsy outside MRI-targeted lesions in 196/767 (25.6%), and combined biopsy in 384/767 (50.1%). Exclusive outside-target systematic csPCa detection occurred in 64/767 men (8.3%), representing 16.7% of all csPCa detected. This rate was highest in PI-RADS 3 lesions (8/30, 26.7%). On multivariable analysis, overall csPCa detection was associated with age, PSA density, and PI-RADS score, whereas exclusive outside-target detection was inversely associated with PI-RADS score and positively associated with procedures performed by urologists. Spatial analysis showed that most systematic-only csPCa lesions were anatomically distinct from the index MRI-visible lesion. CONCLUSIONS: Systematic biopsy outside MRI-targeted lesions detected additional csPCa in 64/767 men (8.3%) and frequently identified anatomically distinct lesions, supporting continued systematic sampling alongside MRI-targeted biopsy in selected patients.