Clinical Usefulness of 18F-Fluorodeoxyglucose Positron Emission Tomography in the Diagnostic Algorithm of Advanced Entero-Pancreatic Neuroendocrine Neoplasms

Background. The role of F-18-fluorodeoxyglucose positron emission tomography (F-18-FDG PET) in the diagnostic algorithm of entero-pancreatic neuroendocrine neoplasms (EP NENs) is unclear because most available data derive from heterogeneous populations in terms of tumor biology and disease status at time of examination. The aim of this study was to determine the ability of F-18-FDG PET to identify patients with more aggressive disease among those with advanced EP NENs.Subjects, Materials, and Methods. Patients with advanced EP NENs and known disease status (progressive disease [PD] or stable disease [SD]) according to imaging procedures, who received F-18-FDG PET and computed tomography scans during a time frame of 1 month, were included.Results. A total of 93 patients, including 69 patients with pancreatic NENs and 24 patients with small-intestine NENs, were included. At the time of study entry, 64 patients (68.8%) had PD, and the remaining 29 patients (31.2%) had SD. A total of 62 patients (66.7%) had positive F-18-FDG PET, whereas F-18-FDG PET was negative in the remaining 31 patients (33.3%). Overall, F-18-FDG PET sensitivity and specificity to detect PD were 90.6% and 86.2%, respectively, resulting in a diagnostic accuracy of 89.2%. A positive F-18-FDG PET was significantly associated with PD at the time of study entry (p<.0001 at multivariate analysis). Although a higher proportion of F-18-FDG PET-positive examinations were observed in patients with higher tumor grade (p=.01), 53.8% of patients with grade 1 neuroendocrine tumors (NETs) had positive F-18-FDG PET, and 37.5% of patients with grade 2 NETs had negative F-18-FDG PET. Overall survival was significantly shorter in F-18-FDG PET-positive patients (median: 60 months) in comparison with F-18-FDG PET-negative patients (median not reached; p=.008).Conclusion. F-18-FDG PET has a high diagnostic accuracy to identify progression of disease with unfavorable clinical outcome in patients with advanced EP NENs. Knowledge of disease status and G grading are key factors for physicians to better select patients for whom F-18-FDG PET is clinically useful.