Objectives:

Primary liver tumors constitute one of the most common tumors. These are aggressive tumors with poor survival. Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT), most commonly used functional imaging, shows limited tracer retention and poor tumor to background ratios (TBR). Novel ⁶⁸Ga-fibroblast-activation-protein inhibitor (FAPI) PET/CT has shown better tracer uptake and detection efficacy in liver tumors. However, most of the available literature is limited to single center studies with limited number of patients. So, we tried to review and analyze the head-to-head comparison of ¹⁸F-FDG PET/CT and 68Ga-FAPI PET/CT in evaluation of liver tumors.

Methods:

Literature available on head to head comparison of diagnostic accuracy of ¹⁸F-FDG PET/CT and ⁶⁸Ga-FAPI PET/CT was searched in databases like PubMed, SCOPUS, EMBASE and Google Scholar for published original studies till April 2023. The relevant studies were selected and assessed using the Revised Tool for the Quality Assessment of Diagnostic Accuracy Studies-2 checklist. A random-effect model was used for calculating pooled sensitivity and specificity. They were represented with 95% confidence intervals (95% CI) and demonstrated in Forest plots. I-square statistic was used to assess heterogeneity in the studies.

Results:

Pooled sensitivity and specificity of FAPI PET/CT and ¹⁸F-FDG PET/CT for detection of primary liver tumors was 94.3% (95% CI: 90.6- 96.8%); 89.3% (95% CI: 71.8-97.7%) and 56.1% (95% CI: 49.7-62.5%); 96.4% (95% CI: 81.7-99.9%) respectively. Pooled sensitivity for detection of extrahepatic metastatic disease was 92.2% (range: 88.1-100%; 95% CI: 87.8-95.4%) and 72.4% (range: 69.8-76.5; 95% CI: 65.9-78.2%) respectively. Also, the maximum standardized uptake value (SUV_max) and TBR were higher for FAPI PET/CT than ¹⁸F-FDG PET/CT in the included studies.

Conclusion:

Overall, FAPI PET/CT showed higher sensitivity for detection of liver tumors with better SUV_max and TBR than ¹⁸F-FDG PET/CT.

Keywords: Positron emission tomography/computed tomography, 18F-fluorodeoxyglucose, fibroblast-activation-protein inhibitors, liver cancers, hepatocellular cancer, cholangiocarcinoma