Role of Combined [(68)Ga]Ga-DOTA-SST Analogues and [(18)F]FDG PET/CT in the Management of GEP-NENs: A Systematic Review

Gastro-entero-pancreatic neuroendocrine neoplasia (GEP-NENs) are rare tumors, but their frequency is increasing. Neuroendocrine tumors normally express somatostatin (SST) receptors (SSTR) on cell surface, especially G1 and G2 stage tumors, but they can show a dedifferentiation in their clinical history as they become more aggressive. Somatostatin receptor imaging has previously been performed with a gamma camera using [(111)In]In or [(99m)Tc]Tc-labelled compounds, while [(68)Ga]Ga-labelled compounds and PET/CT imaging has recently become the gold standard for the diagnosis and management of these tumors. Moreover, in the last few years (18)F-fluorodeoxyglucose ([(18)F]FDG) PET/CT has emerged as an important tool to define tumor aggressiveness and give relevant prognostic information, particularly when coupled with [(68)Ga]Ga-labelled SST analogues PET/CT. This review focuses on the importance of combined imaging with [(68)Ga]Ga-labelled SST analogues and [(18)F]FDG for the management of GEP-NENs.