Purpose: 68Ga-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 68Ga-FAPI-04 for detecting and characterizing hepatic nodules in patients with suspected carcinoma.
Methods: Twenty-five patients showing suspicious hepatic lesions for malignancy underwent 68Ga-FAPI-04 PET. The maximum and mean standardised uptake values (SUVmax, SUVmean) were measured for all detected lesions and normal hepatic tissues, respectively. The target-to-background ratio (TBR) was calculated by dividing the lesion SUVmax with the SUVmean 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 SUVmax 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 (SUVmax = 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: 68Ga-FAPI-04 showed high sensitivity in detecting hepatic malignancies, particularly in poorly differentiated forms with concordantly elevated FAP expression.
Keywords: 68Ga-FAPI-04; Fibroblast activating protein; Hepatic nodule; Hepatocellular carcinoma.