Identification and Localization of Functioning Gastroenteropancreatic Neuroendocrine Tumors Using [18F]F-NOTA-octreotide PET/CT.

Accurate identification and localization are crucial for determining surgical strategies in patients with F-GEP-NETs, as these tumors often cause specific clinical syndromes due to hormone overproduction. However, conventional anatomical imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), exhibit low sensitivity and accuracy in detecting and localizing F-GEP-NETs. This limitation stems from the frequent small size and inherent imaging heterogeneity of such tumors, which often lead to inconclusive or false-negative results. Herein, we present two illustrative cases of F-GEP-NETs (one gastrinoma and one VIPoma) that were either not visualized or yielded undefined findings on contrast-enhanced CT (CE-CT). In both instances, [18F]F-NOTA-octreotide PET/CT subsequently enabled precise identification and anatomical localization of the primary tumors. This molecular imaging technique leverages the overexpression of somatostatin receptors on the surface of most neuroendocrine tumor cells, providing superior functional characterization. These cases underscore the potential diagnostic value of [18F]F-NOTA-octreotide PET/CT in the clinical workup of patients with biochemically confirmed F-GEP-NETs in whom conventional imaging is non-diagnostic, thereby aiding in the formulation of optimal treatment strategies and personalized management plans.