68Gallium-FAPI-positron emission tomography for dignity assessment of mass-forming chronic pancreatitis and pancreatic ductal adenocarcinomas compared to laboratory parameters, ultrasound and computed tomography

Purpose: The differentiation of mass-forming chronic pancreatitis (MFCP) and pancreatic ductal adenocarcinomas (PDAC) based on conventional imaging methods like ultrasound, CT and MRI is frequently not possible. Here, we applied static (60 minutes post injection) and dynamic PET/CT with ⁶⁸ Gallium-labelled Fibroblast Activated Protein Inhibitors ( ⁶⁸ Ga-FAPI-PET/CT) in 26 preoperative, treatment-naive patients with unclear pancreatic masses to evaluate its potential diagnostic value for MFCP and PDAC. Methods: 26 Patients underwent static and dynamic ⁶⁸ Ga-FAPI-PET/CT as well as dedicated fundamental (US) and contrast-enhanced ultrasonography (CEUS) before surgical resection or biopsy of pancreatic masses and subsequent histological analyses. Static parameters (SUVmax and SUVmean and target to background ratios) were generated from VOIs of pancreatic masses. Time activity curves and dynamic parameters were extracted from dynamic PET data. Results: Histology revealed 12 PDAC, 2 high-grade IPMN and 12 MFCP. We observed higher ⁶⁸ Ga-FAPI-uptake in PDACs (average SUVmax/mean 18.09 +/- 5.5 / 10.55 +/- 2.97) than in MFCP (average SUVmax/mean 11.55 +/- 3.88 / 6.83 +/- 2.20). In dynamic PET-imaging, PDAC and MFCP showed differential time activity curves and the average time to peak was markedly longer for PDAC (1094 +/- 945 seconds ) than for MFCP (449 seconds +/- 203). In ROC curves, static and dynamic imaging parameters showed higher sensitivity and specificity than laboratory parameters, CT- and US-size. Conclusion: ⁶⁸ Ga-FAPI-PET/CT displays the fibrotic activity of MFCP. Static and dynamic ⁶⁸ Ga-FAPI-PET/CT should be considered, when clinical parameters and other imaging methods are not able to distinguish between PDAC and MFCP.