Chapter 5 - Gastroenteropancreatic Neuroendocrine Neoplasms

Abstract

Neuroendocrine neoplasia (NEN) could arise from anywhere in the body but arises mainly (about 70%) from the gastroenteropancreatic (GEP) system. In addition to clinical information, benign findings, pitfalls in PET/CT reading using various radiotracers, and teaching cases, this chapter reviews evidence-based recommendations regarding PET/CT examination in NENs and compares them with statements in major clinical guidelines. High expression of predominantly SSTR-2 and SSTR-5 on more than 70% of gastrointestinal NENs makes them excellent targets for imaging with radiolabeled somatostatin analogues such as 111In-octreotide scan. In patients with suspect thoracic and GEP-NETs, 68Ga-somatostatin receptor PET/CT shows high sensitivity, specificity, and accuracy and should be considered as a first-line diagnostic imaging modality. It is also promising for assessing SSRTs before peptide receptor radiolabeled therapy (PRRT) and therapy evaluation after PRRT. As another modality, 18F-DOPA PET/CT is an accurate method for diagnosing proven or suspected NENs. Given low proliferation and high differentiation, neuroendocrine tumors (NETs) are usually faintly FDG avid. But FDG PET/CT is recommended for staging and restaging of selected patients with poorly differentiated NENs, i.e., neuroendocrine carcinomas G3. FDG PET/CT may be useful to characterize tumor aggressiveness with higher FDG uptake (higher standard uptake values), which indicates a worse prognosis. Some other PET radiotracers are also used to image this kind of malignancy.