Prospective evaluation of the utility of concurrent 18F-FDG PET/CT and 68Ga-DOTA-TOC imaging in gastroenteropancreatic neuroendocrine neoplasms (GEPNENs): The PETNET study

4022 Background: Somatostatin receptor imaging (SRI) is a standard of care for patients with GEPNETs. The additional value of concurrent 18F-FDG PET/CT (FDG PET) remains unclear. We reviewed a prospective functional imaging study to determine the utility of FDG PET in GEPNENs. Methods: PETNET is a prospective study in British Columbia, Canada, which provides all 68Ga-DOTA-TOC (DOTA PET) imaging in the province. Every patient receives a DOTA PET scan and an FDG PET within 30 days. PETNET enrolls all patients with an indication for SRI. Scans are ordered per treating physician discretion at any point in the disease course. This abstract focuses on the WD-GEPNEN population. Only the first dual functional imaging scans were analyzed and FDG was interpreted qualitatively (positive/negative). Results: From 04/2017-01/2023, 375 patients with NEN were enrolled, 165 (44%) with metastatic GEPNENs. Baseline characteristics are described. Median time between scans was 4 days (IQR 1-11). The proportion of patients with positive FDG PET at baseline increased with WHO grade. For patients with well differentiated G1 to G3 GEPNENs (N=161), overall survival was significantly lower with a positive FDG PET (HR: 4.22; 95%CI 1.61-11.02 p=0.001). FDG remained prognostic when G3 tumors were excluded (N=148) (HR 3.52; 95%CI 1.32-9.42 p= 0.007). When analyzing dual tracer PET imaging, patients with DOTA+/FDG- had reduced risk of dying in comparison with DOTA+/FDG+ (HR:0.26; 95%CI 0.09-0.67 p=0.01). After multivariate analysis, FDG positivity remained independently associated with reduced survival (HR 2.87; 95%CI 1.06-7.75 p=0.04) when controlling for grade of tumor and age. Conclusions: In this prospective cohort of metastatic GEPNENs, a positive FDG PET was significantly associated with reduced overall survival. These results provide additional evidence to support dual tracer functional imaging use in metastatic well differentiated GEPNEN’s. [Table: see text]