Diagnostics of neuroendocrine tumours.

Neuroendocrine tumours (NETs) are rare pathologies which origin from neuroectodermic and endodermic cells and that can produce peptides and amino acids. About 70% of NETs derive from gastroenterohepatic (GEP) system and the other 30% from the different sites through the body. They are distinguished into single and multiple localizations and also into sporadic, familial multiple endocrine-related forms and recurrent forms. Moreover, when they produce hormones they usually are symptomatic; yet, they are characterized by the synthesis and secretion in the blood stream of several tumor-specific markers or can express somatostatin receptors in their cellular surface. The diagnosis and follow-up of NETs rely on laboratory studies, histopathology and the combination of anatomical and functional imaging, with the latter being the main method for monitoring response to therapy. In recent years, nuclear medicine has contributed to the impressive development of the knowledge of NETs in terms of biology (receptor scintigraphy), pharmacology (development of new tracers) and therapy (radiometabolic therapy). Nuclear medicine procedures for diagnosis and treatment of NETs are based on the biological properties of these tumours: the expression of somatostatin receptors. Somatostatin receptor scintigraphy not only has a crucial role in diagnosis and staging of NETs, but also in assessing suitability for treatment with cold and radiolabelled somatostatin analogues, as well as in monitoring response to treatment and detecting recurrent disease. In conventional nuclear medicine, the two most important functional imaging modalities are ¹¹¹In-octrescan and ¹²³I-MIBG. Over the last 5 years, due to the development of new tracers, such as ⁶⁸Ga labelled-DOTA-peptides PET and ¹⁸F-DOPA, PET has also been employed with significant benefits in the diagnosis and management of NETs.