Fibroblast imaging of hepatic carcinoma with 68Ga-FAPI-04 PET/CT: a pilot study in patients with suspected hepatic nodules

Purpose 68 Ga-FAPI-04 is a rapidly evolving PET tracer for whole-body imaging in a variety of cancers. We aimed to evaluate the diagnostic performance of 68 Ga-FAPI-04 for detecting and characterizing hepatic nodules in patients with suspected carcinoma. Methods Twenty-five patients showing suspicious hepatic lesions for malignancy underwent 68 Ga-FAPI-04 PET. The maximum and mean standardised uptake values (SUV max , SUV mean ) were measured for all detected lesions and normal hepatic tissues, respectively. The target-to-background ratio (TBR) was calculated by dividing the lesion SUV max with the SUV mean of non-tumour liver tissue. Lesion uptake value was correlated with the in vitro hepatic FAP expression determined by immunohistochemistry (IHC). Results In total, 17 patients who underwent surgery or biopsy were recruited for the final analysis. A total of 28 intrahepatic malignant lesions were detected in 16 patients; the mean SUV max was 8.36 ± 4.21 (range 2.21 to 15.86), and mean TBR was 13.15 ± 9.48 (range 2.79 to 38.12) in all detected lesions ( n  = 28). One benign patient showed negligible hepatic uptake (SUV max  = 0.47), whereas 75% of the primary intrahepatic hepatocellular carcinoma (HCC) lesions ( n  = 6) showed prominent FAP expression, 12.5% of the lesions ( n  = 1) showed moderate expression in stromal cells, and one showed negligible expression. Conclusions 68 Ga-FAPI-04 showed high sensitivity in detecting hepatic malignancies, particularly in poorly differentiated forms with concordantly elevated FAP expression.