Clinical Value Of ⁶⁸Ga-FAPI-04 PET/CT In Diagnosis And Differential Diagnosis Of Pancreatic Cancer

Objective:To explore the application value of ⁶⁸Ga-FAPI-04 PET/CT in the differential diagnosis of pancreatic cancer and pancreatitis,as well as the distribution of false positive lesions of non-malignant tumors found in imaging and analyze the causes,so as to provide some help for nuclear medicine doctors when interpreting ⁶⁸Ga-FAPI-04 PET/CT images.Methods:The imaging data of the patients with positive pancreatic uptake who underwent ⁶⁸Ga-FAPI-04 PET/CT imaging from September 2020 to March2021 in the Department of Nuclear Medicine of the Affiliated Hospital of Southwest Medical University were retrospectively analyzed.The cases were grouped according to postoperative pathology,medical history,blood amylase,serum tumor markers,color ultrasound and MRI examination,and follow-up,and the patients who had been treated were excluded（because different treatment methods may have different effects on the uptake of tracers）.A total of 61 cases were finally included in the study,including pancreatic cancer group（16 cases）,acute pancreatitis group（12 cases）,chronic pancreatitis group（11 cases）,non-specific uptake group or physiological uptake group（22 cases）,and the four groups of cases were analyzed.Then,the imaging data of 547cases of ⁶⁸Ga-FAPI-04 PET/CT patients in the nuclear medicine department of the Affiliated Hospital of Southwest Medical University from September 2020 to March 2021 were retrospectively analyzed.Two experienced physicians analyzed the clinical data,relevant imaging examinations,laboratory examinations,pathological results and follow-up results of patients,and discussed the distribution of false positive lesions of non-malignant tumors found in imaging and analyzed the causes.Results:There was significant difference in SUVmax between the four groups（P<0.05）.Compared with Post hoc,the SUVmax values of acute pancreatitis group and pancreatic cancer group were significantly higher than those of chronic pancreatitis group and non-specific uptake group.SUVmax in chronic pancreatitis group was higher than that in nonspecific intake group（P<0.05）.When the Youden index is 0.773,the SUVmax boundary value is 6.45.At this time,the corresponding sensitivity of ⁶⁸Ga-FAPI-04 PET/CT is 90.9%,the specificity is 86.4%,the accuracy is 87.9,the positive predictive value is76.9%,and the negative predictive value is 95.0%.The difference of SUVmax between acute pancreatitis group and pancreatic cancer group was not statistically significant,but it could be identified by taking the form of tracer and CT.The size of pancreatic cancer was positively correlated with the SUVmax value.Among 547 patients undergoing ⁶⁸Ga-FAPI-04 PET/CT examination,142 were falsely positive.Thirteen patients underwent surgical resection and were diagnosed as false positive lesions based on postoperative pathology.Among them,there was 1 case of thyroiditis,2 cases of pulmonary tuberculosis,1 case of bone tuberculosis,2 cases of inflammatory pseudotumor,1 case of pulmonary sarcoidosis,1 case of pulmonary benign fibroma,1 case of organizing pneumonia,2 cases of renal vascular smooth muscle lipoma,1 case of pancreatitis,and 1 case of pancreatic mucinous cystadenoma.129 cases were diagnosed as false positive lesions through medical history,relevant imaging examinations,and long-term follow-up,including 8 cases（6.2%）in the neck,13 cases（10.1%）in the chest,25 cases（19.4%）in the abdomen,80 cases（62.0%）in the bones and joints,and 3 cases（2.3%）in the skin.In the false positive imaging,134 cases（94.4%）showed uptake related to inflammation,with arthritis（31 cases）and osteophytes（44 cases）being the most common;There were 8 cases（5.6%）of uptake related to fibroblasts.Conclusion:⁶⁸Ga-FAPI-04,as a new tracer,has great potential in the diagnosis of pancreatic cancer through PET/CT imaging,and has important value in differentiating benign and malignant pancreatic lesions.However,it is not a tumor specific imaging agent,and there will be non-malignant tumor false positive imaging,mainly related to inflammation and fibroblasts.