Therapy of NET with radiolabeled SST analogs

Neuroendocrine Tumors (NETs) include a large heterogeneous group of cancers, mainly rising from the digestive tract. Their incidence has significantly increased over the last decades, as a consequence of the availability of novel diagnostic techniques and the improving knowledge in this field. Their prognosis mainly depends on tumor grading, primary tumor site, tumor staging, and expression of somatostatin receptors (SSTRs) on the surface of well-differentiated NETs. This characteristic represents the basis for both diagnosis (with both single-photon emission tomography and positron emission tomography radiopharmaceuticals) and treatment with radiolabeled somatostatin analogs (SSAs). Therefore, nuclear medicine plays a crucial role in the pre-treatment assessment of the expression of SSTRs on the tumor surface, thus providing undeniable information for the selection of patients candidates to peptide receptor radiotherapy (PRRT) with β-emitters such as 90Y or 177Lu. PRRT has shown to be effective in patients with unresectable or metastatic, progressive, well differentiated, SSRs positive gastroenteropancreatic neuroendocrine tumors (GEP-NETs). Therefore, PRRT can be used as a second-line treatment, after failure of first-line treatment with “cold” SSAs. In this chapter we will provide an overview of the most commonly applied radiopharmaceuticals for imaging of SSRs and for therapy of NETs and we will provide important and practical aspects that must be considered before planning a PRRT.