Abstract
3034
Introduction: Fibroblast activation protein inhibitor (FAPI) analogs are newly introduced PET agents for cancer imaging. As a preliminary result of a human PET study for [18F]FAPI-74, a fluorine-labeled agent, we assessed potential pitfalls in interpreting pancreaticobiliary cancer.
Methods: Fourteen patients who had been diagnosed with pancreas or common bile duct (CBD) cancer were prospectively enrolled (11 for pancreatic cancer and 3 for CBD cancer). [18F]FAPI-74 PET images were acquired 60 min and 120 min after the injection. Images were analyzed by qualitative and quantitative methods. Gallbladder (GB), biliary duct, normal pancreatic parenchyma were organs of interest in quantitative analysis. We regarded accumulation higher than liver uptake as physiologic FAPI accumulation. A volume of interest (VOI) of GB was drawn to include GB in three planes. A relative threshold of 40% of SUVmax was applied to measure FAPI-active-volume (FAV) and Total-lesion-FAPI-uptake (TLF). In both 60-min and 120-min images, three 5 mm spherical VOIs were drawn in each of the biliary duct and pancreas. Average SUVmax and SUVmean of three spherical VOI were used for quantitative analysis. Wilcoxon signed-rank test was used for statistical analysis
Results: [18F]FAPI-74 accumulation in the GB lumen was seen in 7/10 (70%) of pancreas cancer patients and 1/3 (33.3%) of CBD cancer patients. A patient with pancreatic cancer underwent cholecystectomy. [18F]FAPI-74 accumulation in biliary duct was seen in 10/11 (90.9%) and 2/3 (66.7%) of CBD cancer patients. FAPI-uptake in normal pancreas parenchyma was seen in 5/11 (45.4%) of pancreas cancer and 1/3 (33.3%) of CBD cancer patients. All of GB uptake were similar or higher than primary tumor uptake. SUVmax and SUVmean of biliary duct and pancreas were statistically significantly decreased at 120-min. SUVmax, SUVmean, FAV, and TLF of GB were increased at 120-min. FAV and TLF show statistical significance.
Conclusions: [18F]FAPI-74 accumulation in GB, biliary duct, and pancreas could be a pitfall in interpreting images for pancreaticobiliary cancer. The comprehensive interpretation of the accumulation pattern in biliary system through quantitative analysis and delay scan could be required for [18F]FAPI-74 PET imaging.
