The Role of 68Ga FAPI-04 and 18F-FDG PET/CT in Detecting Liver Metastases in Different Types of Cancer.

Objective: We compared the diagnostic accuracies of Ga FAPI-04 PET/CT and F-FDG PET/CT for detecting liver metastases (LMs) in patients with different cancer types.

Materials And Methods: This retrospective study included 63 patients with liver lesions who underwent F-FDG PET/CT and Ga-FAPI-04 PET/CT between May 2020 and May 2022. Patients with histopathologically confirmed primary diagnoses, data that could be accessed retrospectively, liver lesions confirmed by biopsy over at least 3-6 months of follow-up (via ultrasonography, CT, magnetic resonance imaging, PET/CT, or laboratory tests) were included. Patients with secondary malignancies or primary liver malignancies, and/or who could not be followed-up, were excluded.

Results: Of the 63 total patients, 34 (54%) were female, and the mean age was 61 (30-92) years. There were 582 LMs in 51 patients and 35 benign liver lesions in 20 (12 patients had only benign and 8 both benign and malignant lesions). Of the 582 LMs, 472 (81.1%) evidenced F-FDG uptake and 572 (98.2%) Ga-FAPI uptake. The diagnostic accuracies of Ga-FAPI PET/CT and F-FDG PET/CT were 98% and 82%, respectively (p < 0.001; McNemar test). When the LMs were compared, the maximum standardized uptake (SUVmax) value was significantly higher on F-FDG PET/CT than Ga-FAPI PET/CT (median: 6.0 vs. 5.4; p = 0.016). However, the LM-to-background ratio (TBR) was significantly higher on Ga-FAPI PET/CT than F-FDG PET/CT (median: 4.1 vs. 2.1; p < 0.001).

Conclusion: Ga-FAPI PET/CT detected more LMs than did F-FDG PET/CT, and TBR was significantly higher on Ga-FAPI PET/CT than F-FDG PET/CT.