Baseline Characteristics and Utility of Pretherapeutic Fluorodeoxyglucose-PET for Pancreatic Cancer.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive and lethal malignancy. Surgical resection is the only curative modality combined with neoadjuvant chemotherapy to improve survival. Given the limitations of traditional responses like cross-sectional imaging (CT/MRI) or tumor markers, carbohydrate antigen 19-9 (CA19-9), the 2023 National Comprehensive Cancer Network (NCCN) guidelines included fluorodeoxyglucose-positron emission tomography (FDG-PET) as an adjunct to assess response to neoadjuvant chemotherapy. There are common misconceptions on the metabolic activity (tumor avidity) in PDAC, so we aimed to describe the baseline characteristics and utility of FDG-PET in a cohort of treatment naïve PDAC patients. A single center retrospective study was conducted capturing all biopsy proven, treatment naïve PDAC patients that underwent either baseline FDG-PET/CT or FDG-PET/MRI imaging between (2008-2023). Baseline FDG-PET characteristics were collected, including primary tumors' maximum standardized uptake value (SUVmax) defined as metabolic activity (FDG uptake) of tumor compared to surrounding pancreatic parenchymal background, and the identification of extra-pancreatic metastatic disease. We identified 1095 treatment naïve PDAC patients that underwent baseline FDG-PET imaging at diagnosis. CA19-9 was elevated in 76% of patients. Overall, 96.3% (n=1054) of patients had FDG-avid tumors with a median SUVmax of 6.4. FDG-PET also identified suspicious extrapancreatic metastatic lesions in 50% of patients, with a higher proportion (p < 0.001) in PET/MRI (59.9%) vs. PET/CT (44.3%). After controlling for CA19-9 elevation, PET/MRI was superior in detection of extrapancreatic lesions compared to PET/CT. FDG-PET has significant utility in PDAC as a baseline imaging modality prior neoadjuvant therapy given the majority of tumors are FDG avid. Furthermore, FDG-PET can identify additional extrapancreatic suspicious lesions allowing for optimal initial staging, with PET/MRI having increased sensitivity over PET/CT.