This review article summarizes the role of combined 68Ga DOTA-peptides and 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in the evaluation of gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs). Patients with GEP-NENs can initially present themselves to a gastroenterologist or endocrinologist rather than cancer specialist; hence, it is vital for a wider group of clinicians to be familiar with the range of tests available for the evaluation of these patients. The role of PET scanning by using 68Ga DOTA-peptides has a high sensitivity in the diagnosis of GEP-NENs and to guide patient selection for treatment with somatostatin analogues (SSA) and/or peptide receptor radionuclide therapy (PRRT). The loss of somatostatin receptor (SSTR) expression was found to be associated with an increased glucose metabolism in cells. However, the routine use of SSTR targeted radiotracers in combination with 18F-FDG to evaluate glucose utilization in GEP-NENs is still debatable. In our opinion, in patients with NENs, 18F-FDG PET should be performed in the case of a negative or slightly positive 68Ga DOTA-peptides PET scan for assessing the dedifferentiation status, to guide correct therapeutic strategy and to evaluate the prognosis. The approach of combined receptor and metabolic imaging can improve diagnostic accuracy, especially considering the heterogeneity of these lesions. Therefore, 68Ga DOTA-peptides and 18F-FDG PET should be considered complementary in patients with GEP-NENs.
Keywords: FDG PET; GEP-NENs; SSTR PET; neuroendocrine tumors.