The addition of PSMA PET in selecting candidates for prostate cancer focal therapy.

Objectives: This study aims to evaluate whether prostate-specific membrane antigen (PSMA) PET improves detection of index lesions and refines patient selection for focal therapy (FT) compared with standard diagnostic pathways. Patients and methods: We performed a retrospective review of men who underwent radical prostatectomy (RP) between 2015 and 2023. Pre-operative assessment included multiparametric MRI, PSMA PET/CT and transperineal prostate biopsy. RP whole-mount histopathology served as the reference standard. Focal therapy eligibility was assessed, and diagnostic performance compared between standard-of-care selection criteria and criteria incorporating PSMA PET. Results: Sixty patients (26%) met SOC criteria for FT. On final RP histopathology, only 20/60 (33.3%) were truly eligible, with discordance most commonly due to bilateral clinically significant prostate cancer (80%). Incorporation of PSMA PET into the selection model improved specificity for appropriate FT selection from 80.3% to 89.7% and positive predictive value from 33.3% to 46.2%. For detection of outfield disease, addition of PSMA PET increased sensitivity to 75.5% and negative predictive value to 53.5%. Higher SUVmax was significantly associated with FT ineligibility (AUC 0.67), with an optimal cut-point of SUVmax > 4.78 predicting unsuitable candidates. Conclusion: Only a small proportion of men fulfil criteria for focal therapy, with a high risk of bilateral or contralateral disease using MRI and biopsy alone. PSMA PET improves diagnostic accuracy by identifying outfield lesions and reducing inappropriate FT selection. These findings support integration of PSMA PET to optimise patient selection, with further studies in prospective focal therapy cohorts required.