Efficacy of [Ga]Ga-FAPI-PET as a non-invasive evaluation method of liver fibrosis.

Introduction: Liver fibrosis is a chronic fibrosing hepatic disorder following recurrent injury, characterized by the excessive accumulation of extracellular matrix. Early detection has a great clinical impact because 80-90% of hepatocellular carcinomas are known to develop in fibrotic or cirrhotic (end-stage fibrotic) livers. PET imaging with FAP ligands exhibited highly promising results in recent years to visualize fibrosis in various organs due to the crucial role of activated fibroblasts in fibrosing processes. However, still little is known about the efficacy of FAP imaging in liver fibrosis. Thus, we sought to investigate the potential of FAPI-PET in a cohort of oncological and non-oncological patients.

Methods: 199 patients who underwent FAPI-PET/CT at the University Hospital of Heidelberg between July 2017 and July 2020 were retrospectively analyzed. The tracer uptake of the liver was analyzed and correlated with radiological and clinical parameters.

Results: We observed a weak but significant negative correlation between the hepatic FAPI uptake and CT density (r = - 0.273, P < 0.001***). A positive correlation was observed between hepatic FAPI uptake and the aspartate aminotransferase (AST)-to-platelet ratio index (APRI) (r = 0.183, P = 0.009**), an established surrogate for liver fibrosis. The liver SUV (standardized uptake value) mean and SUVmax of FAPI showed significant differences between groups of patients with low (< 0.5), middle (0.5-1.0) and higher (> 1.0) levels of APRI (both P < 0.001***).

Conclusion: These preliminary observational results suggest that FAPI-PET may be a viable non-invasive method to asses liver fibrosis.