Clinical value of 18F FDG bio-distribution in metabolic characterization of pancreatic masses on PET/CT

Aim: The aim of this study was to research the role of possible effect of current metabolic-clinical factors and scan parameters on 18F FDG distribution, detection of tumor foci and to investigate contribution to the sensitivity of 18F FDG PET/CT in cases which 18F FDG PET/CT perfomed for initial evaluation of pancreatic mass. Materials and Methods: Patients which referred to Ege University Department of Nuclear Medicine for metabolic characterization of pancreatic mass between July 2012 and January 2019, were retrospectively evaluated with pathological and radiological findings. The cases were grouped as benign, pancreatic adenocarcinoma and cases with liver metastasis. From each patient, only one pancreatic lesion and one liver metastasis if detected were included. Scan parameters of patients, SUVmax values of lesions and physiological distribution areas, laboratory and imaging parameters of patients were noted. Data analysis was performed using IBM SPSS Statistics 22.0 Program. Findings: The study included 162 patients with 17 benign, 145 patients with adenocarcinoma and 47 patients with liver metastasis. In the patient group diagnosed with adenocarcinoma, primary pancreatic lesion of 9 patients did not show 18F FDG uptake. The median SUVmax of benign pancreatic lesions was 4.2 (1-10.7) and the SUVmax of malignant pancreatic lesions was 9.6 (1.5-65). In the patient group with liver metastasis, 13 patients had a lesion larger than one centimeter and compatible with liver metastasis that could not be detected in 18F FDG PET / CT scan. Blood glucose values were higher and SUVmax cerebrum values were found to be lower in patients with undetectable tumor lesions. (p<0,001). The SUVmax cerebrum value which predicted the presence of primary or metastatic lesions that could not be detected was 8.2 for the whole patient group, and 7.2 for the patients with blood glucose levels of higher than 120 mg/dl. Sensitivity of PET / CT for detection of primary pancreatic malignancy calculated and found to be 94% for the whole patient group, and 90% for the patients with blood glucose levels higher than 120 mg / dl. When patients with values below SUVmax cerebrum thresholds based on blood glucose levels were excluded from the study, the sensitivity of the examination was calculated as 98% -95%, respectively. Results: Although SUVmax values of benign and malignant pancreatic lesions were shown to be statistically different from each other, it was observed that the value ranges were partially overlapping between the two groups. In our study, it was shown that among the pancreatic adenocarcinomas, SUVmax cerebrum value was similarly affected in cases which 18F FDG uptake was affected by blood glucose levels, and false negative cases could be predicted according to SUVmax cerebrum level in patients with elevated blood glucose levels. In the light of this information, it was concluded that the reason for the differences in sensitivity between the studies reported in the literature can be explained. Keywords: Fluorodeoxyglucose F18, Positron Emission Tomography Computed Tomography, Pancreas, Adenocarcinoma