Dual targeting PET tracer [⁶⁸Ga]Ga-PSFA-01 in patients with prostate cancers: A pilot exploratory study

Purpose: To assess the effectiveness of [⁶⁸Ga]Ga-PSFA-01 PET/CT in detecting primary tumors and metastatic lesions in patients with prostate cancer (PCa), and to compare the results with those from [⁶⁸Ga]Ga-PSMA-11 PET/CT and [⁶⁸Ga]Ga-FAPI-04 scans. Methods: Patients with histologically proven PCa were prospectively recruited and underwent [⁶⁸Ga]Ga-PSFA-01 PET/CT, of which: 25 participants also underwent [⁶⁸Ga]Ga-PSMA-11 PET/CT scan, 5 patients also underwent [⁶⁸Ga]Ga-FAPI-04 PET/CT scan, 3 patients underwent three modalities imaging. To assess the expression of PSMA and FAP, we obtained a pathological tissue section from a patient and performed immunohistochemical staining analysis. SUV_max-PSFA, SUV_max-PSMA, SUV_max-FAPI and the number of detected lesions were compared by using the Wilcoxon signed-rank test, and the Mc-Nemar test was used to compare detectivity. Correlation between SUV_max-PSFA and prostate cancer related clinical indicators was demonstrated with Spearman's ratio. A visual assessment was made to compare the detectability of primary tumors and metastases in different regions. Results: A total of 33 patients with a median age of 70 years (range: 52-89 years) were enrolled. Including 13 patients for initial staging and 20 for recurrence detection. [⁶⁸Ga]Ga-PSFA-01 demonstrated superior performance in both patient-based and lesion-based analyses than [⁶⁸Ga]Ga-PSMA-11 PET/CT. However, [⁶⁸Ga]Ga-PSFA-01 depicted lower uptake in primary tumors (11.13 ± 7.04 vs. 15.44 ± 9.25, p = 0.009), bone metastases (8.50 ± 5.0 vs. 12.43 ± 9.55, p < 0.001) and metastases in other sites (6.05 ± 3.29 vs. 10.73 ± 8.74, p = 0.028) , lower tumor to background ratio (TBR) than [⁶⁸Ga]Ga-PSMA-11 PET/CT (2.86 ± 1.50 vs. 9.50 ± 5.62, p < 0.001). [⁶⁸Ga]Ga-PSFA-01 PET/CT showed more lesions (24 vs. 13, p = 0.18), higher uptake (primary tumors, 10.27 ± 2.42 vs. 7.32 ± 0.17, p = 0.109; bone metastases, 8.14 ± 5.98 vs.4.52 ± 1.22, p = 0.128; pelvic lymph nodes, 5.4 ± 2.83 vs.4.19 ± 1.39, p = 0.655) than [⁶⁸Ga]Ga-FAPI-04 PET/CT. There was also a significantly positive correlation between SUV_max-PSFA of prostate lesions with the tPSA levels (r = 0.468, p = 0.016) and fPSA levels (r = 0.518, p = 0.04), a significantly negative correlation with the free-to-total prostate-specific antigen ratio (FPSAR) (r = -0.608, p = 0.012). Conclusion: [⁶⁸Ga]Ga-PSFA-01 PET/CT demonstrated higher detection rates and visual assessment efficacy compared to [⁶⁸Ga]Ga-PSMA-11 PET/CT in PCa patients. While preliminary data suggest that [⁶⁸Ga]Ga-PSFA-01 may also outperform [⁶⁸Ga]Ga-FAPI-04 PET/CT, the sample size for [⁶⁸Ga]Ga-FAPI-04 (n = 5) is limited, and further studies are needed to confirm these findings.