Diagnostic performance of PSMA PET/CT and multiparametric MRI for local prostate cancer recurrence after high-intensity focused ultrasound

PURPOSE: To compare prostate-specific membrane antigen (PSMA) PET/CT and multiparametric MRI (mpMRI) for detecting locally recurrent prostate cancer following high-intensity focused ultrasound (HIFU). MATERIALS AND METHODS: This retrospective, single-center study included 31 patients treated with HIFU who subsequently underwent both mpMRI and ^18F-piflufolastat PSMA PET/CT followed by prostate biopsy. Imaging studies were independently interpreted by a blinded abdominal radiologist. Diagnostic performance metrics were calculated for each modality and for combined imaging, using biopsy as the reference standard. Paired comparisons were performed using McNemar tests. Spearman rank correlation was used to evaluate associations between SUVmax, post-treatment PSA levels, and ISUP grade group. RESULTS: Of 31 patients, 25 (80.7%) had biopsy-confirmed recurrent prostate cancer. Sensitivity was 72.0% for PSMA PET/CT and 76.0% for mpMRI, with identical specificity of 83.3% for both modalities. Overall accuracy was 74.2% for PSMA PET/CT and 77.4% for mpMRI. Combined imaging increased sensitivity to 92.0% and accuracy to 87.1%, with reduced specificity (66.7%). Combined imaging demonstrated significantly higher sensitivity than either modality alone (p < 0.05). SUVmax showed a modest positive correlation with ISUP grade group (ρ = 0.39, p = 0.03), while post-treatment PSA levels showed no significant correlation with imaging or histopathology. CONCLUSION: PSMA PET/CT and mpMRI demonstrate comparable standalone performance for detecting locally recurrent prostate cancer after HIFU. Combined interpretation improves sensitivity and overall accuracy, supporting a complementary role for integrated imaging in post-HIFU surveillance.