PSMA PET Imaging for Prostate Cancer Recurrence After Minimally Invasive Focal Therapy: A Single-Center Retrospective Study.

Abstract

Prostate-specific membrane antigen (PSMA)-targeted PET/CT (PSMA PET/CT) has become the first-line imaging modality used for staging and restaging prostate cancer. Its utility after minimally invasive focal therapy (high-intensity focused ultrasound, laser ablation, cryoablation) remains unclear. This study evaluated PSMA PET/CT for detecting and localizing recurrence after focal therapy. Methods: This retrospective single-center study included patients with prior focal therapy for prostate cancer who underwent 68Ga-PSMA-11 PET/CT for suspected recurrence between 2016 and 2023 without intervening treatment. Three masked readers analyzed whole-body PET/CT images using a per-region (prostate, pelvic nodes, distant metastases) majority rule for per-patient positivity. Interreader agreement was determined using Fleiss κ. In a subcohort of 39 patients with both MRI and biopsy results available within 3 mo of PSMA PET/CT, per-patient and per-segment (12 prostate segments) accuracy was assessed. One masked reader evaluated PET/CT at 60 min (whole-body) and 90 min (pelvic) postinjection, and one prostate MRI expert independently read the MRI scans. Biopsy pathology-confirmed clinically significant prostate cancer, defined as International Society of Urological Pathology grade 2 or greater, served as the reference standard. Results: In total, 112 patients were included. PSMA PET/CT showed 82% positivity for intraprostatic recurrence, 15% for pelvic nodes, and 9% for distant metastases. Interreader agreement was moderate (κ = 0.4; 95% CI, 0.32-0.54). In the subcohort, per-patient sensitivity was 85% for PET vs. 82% for MRI. All cases with an SUVmax of 10 or greater had an ISUP grade group of 3 or greater. Conclusion: PSMA PET/CT effectively localizes prostate cancer recurrence after focal therapy, outperforming MRI on sensitivity.