Clinical value of [18F]AlF-Thretide PET/CT and early-time-point PET acquisition in the detection and staging of prostate cancer

Aim: Recent studies have demonstrated the potential of PET/CT with 18F-labeled ligands targeting prostate-specific membrane antigen (PSMA), as a promising method for prostate cancer (PCa) management. The aim of this study is to assess the clinical value of [18F]AlF-Thretide ([18F]AlF-PSMA-BCH) PET/CT and early time-point PET acquisition for detecting and staging PCa. Materials and Methods: From November 2022 to May 2023, a total of 73 PCa patients were included in our study. Along with whole-body PET/CT conducted at a median time of 76 min (range: 59-139 min) post-injection, a single-bed pelvic early PET/CT scan was performed, starting at a median time of 187 s (range: 161-453 s) post-injection. Visual analysis of the images was performed first, followed by semiquantitative analysis of maximum standardized uptake value (SUVmax) of primary PCa lesions, metastases, bladder, and surrounding tissues on both early and routine time-point PET/CT scans. Results: Among 56 non-surgical patients (either treatment-naive or after androgen deprivation therapy only) who had previously undergone conventional imaging, N staging was revised in 4 cases, and M staging in 2 cases. In 54 patients with bone scans for comparison, 111 lesions on [18F]AlF-Thretide PET/CT and 41 lesions on bone scans were identified as indicative of bone metastases. The median tumor-to-bladder (T/BL) ratios for primary lesions increased from 0.33 (range: 0.03-6.22) on routine time-point PET/CT to 4.66 (range: 0.24-645.00) on early time-point PET/CT. In 94.6% (53/56) of patients, the T/BL ratios were higher on early PET/CT scans than on routine time-point PET/CT scans. However, the SUVmax of surrounding tissues was found to be higher on early PET/CT scans compared to routine PET/CT scans (external iliac vessels: 8.02 ± 1.64 vs. 2.66 ± 0.59; inferior vesical artery branches near the prostate: 4.70 ± 1.09 vs. 2.30 ± 0.49; gluteus maximus muscle: 1.19 ± 0.31 vs. 0.80 ± 0.25). Of the 17 patients who underwent surgery prior to PET/CT, early PET/CT scans improved the detection rate of local recurrences from 2/17 to 5/17. Conclusion: [18F]AlF-Thretide PET/CT was shown to be a valuable imaging modality in the management of patients with PCa. Early PET/CT scans can improve the detection rate of local recurrences and provide additional information for lesions that are challenging to distinguish from urinary uptake on routine PET/CT scans.