Divergent role of (68)Ga-labeled somatostatin analogs in the workup of patients with NETs: AIIMS experience.

Neuroendocrine tumors (NETs) encompass a wide range of rare and heterogeneous neoplasms arising from the neural crest. Diagnosis of NETs is conventionally done by a combination of common clinical symptoms and biochemical evidence of hormonal excess, which these tumors are known to secrete. After a diagnosis of NET is established, a search for its localization is carried out using common morphologic imaging methods such as ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI). The main problem with structural imaging is, however, its inability to distinguish between endocrine and exocrine lesions. Functional imaging of NETs started with use of iodine-131-meta-iodobenzylguanidine ((131)I-MIBG) and has come a long way since. From accurate demonstration of functioning tumors to detection of small and occult lesions, functional imaging has penetrated almost every aspect of NET management. Procedures such as (131/123)I-MIBG, (111)In-Octreoscan and others are rapidly giving way to use of PET/CT based on the superior resolution of the system and the availability of target-specific positron-emitting radiotracers. The availability of (68)Ga from generator-based radionuclide systems, namely (68)Ge/(68)Ga generators, opened up a new era of molecular imaging for NETs. A multitude of somatostatin analogs can be easily radioliganded with (68)Ga using heterocyclic macromolecular bifunctional chelating systems for targeted diagnosis of somatostatin receptor-expressing tumors, used most effectively to date for detection of NETs. This chapter focuses on our experience at the All India Institute of Medical Sciences, New Delhi regarding the divergent roles of (68)Ga-labeled somatostatin analogs in the workup of patients with NETs.