Initial evaluation of [F-18] alpha-methyl tyrosine PET for differential diagnosis of pancreatic lesions

Objectives Differential diagnosis of pancreatic lesions is difficult, because the possibility of pancreatic cancer (PC) is not easily ruled out. To improve the prognosis of patients with pancreatic cancer, determining resectability of the tumor in its early stage is essential. The aim of this study was to evaluate the potential of [F-18] alpha-methyl tyrosine (FAMT) for the differential diagnosis of pancreatic lesions.

Methods FAMT-PET, FDG-PET, CT and MRI were performed in 14 patients. The uptake of tracers was semi-quantitatively evaluated using standardized uptake value (SUV). Results were correlated with the final diagnosis determined by histopathology (5/14), cytology (6/14), or clinical follow-up (3/14). Written informed consent was secured from all patients.

Results Final diagnosis included 7 PC, 4 mass-forming pancreatitis (MFP) and 2 autoimmune pancreatitis (AIP). FDG-PET showed increased uptake in all patients except one with PC. Maximal SUV was 1.01-11.0 in PC (mean, 5.9 ), 1.93-4.76 in MFP (mean, 3.5 ), and 3.66 and 6.39 in AIP. There is no significant difference in the SUV between these 3 groups. FAMT-PET showed increased uptake in one patient (SUV=1.91) and less increased uptake in the others(SUV≤1.3) with MFP and patients with AIP(SUV ≤ 1.62).

Conclusions The present pilot study indicated that benign pancreatic lesions show less uptake of FAMT. FAMT-PET may have potential utility in the differential diagnosis of pancreatic lesions, in cases suspicious of pancreatic cancer with indeterminate findings of conventional imaging and positive FDG-PET.