Impact of 68ga-fapi pet/ct imaging on the therapeutic management of primary and recurrent pancreatic ductal adenocarcinomas

Abstract

Pancreatic ductal carcinoma (PDAC) is a highly lethal cancer, and early detection and accurate staging are critical to prolonging survival. PDAC typically has a prominent stroma including cancer-associated fibroblasts that express fibroblast activation protein (FAP). FAP is a new target molecule for PET imaging of various tumors. In this retrospective study, we describe the clinical impact of PET/CT imaging using 68Ga-labeled FAP-inhibitors (68Ga-FAPI PET/CT) in 19 patients with PDAC (7 primary, 12 progressive/recurrent). Methods: All patients underwent contrast-enhanced CT (ceCT) for TNM staging before 68Ga-FAPI PET/CT imaging. PET scans were acquired 60 min after administration of 150-250 MBq of 68Ga-labeled FAP-specific tracers. To characterize 68Ga-FAPI uptake over time, additional scans after 10 or 180min were acquired in 6 patients. SUVmax and SUVmean values of PDAC manifestations and healthy organs were analyzed. The tumor burden according to 68Ga-FAPI PET/CT was compared with TNM staging based on ceCT and changes in oncologic management were recorded. Results: Compared with ceCT, 68Ga-FAPI PET/ CT results led to changes in TNM staging in 10 of 19 patients. Eight of 12 patients with recurrent/progressive disease were upstaged, 1 was downstaged, and 3 had no change. In newly diagnosed PDAC, 1 of 7 patients was upstaged, and the staging of 6 patients did not change. Changes in oncologic management occurred in 7 patients. Markedly elevated uptake of 68Ga-FAPI in PDAC manifestations after 1 h was seen in most cases. Differentiation from pancreatitis based on static imaging 1 h after injection was challenging. With respect to imaging after multiple time points, PDAC and pancreatitis showed a trend for differential uptake kinetics. Conclusion: 68Ga-FAPI PET/CT led to restaging in half of the patients with PDAC and most patients with recurrent disease compared with standard of care imaging. The clinical value of 68Ga-FAPI PET/CT should be further investigated.