Neuroendokrine Tumoren aus nuklearmedizinischer Sicht

Context: Neuroendocrine tumors (NETs) frequently overexpress specific receptors, transporters, and enzymes that can be imaged with nuclear medicine techniques. This led to the development of a variety of radiopharmaceuticals for imaging and therapy of NETs. Objective: The aim of this article is to provide description of the current diagnostics and therapy of neuroendocrine tumors from a nuclear medicine viewpoint. Methods: Selective review of the literature, analysis of clinical trials. Results: The most commonly used compounds are peptides with specific binding to the somatostatin type 2 receptor (SSTR2) which is overexpressed by the majority of NETs. These peptides can be used for both conventional nuclear imaging and positron emission tomography (PET). The advantages of PET include higher sensitivity for the detection of primary and metastatic NETs, significantly lower radiation exposure, and markedly shorter duration of the examination. Other radiopharmaceuticals in clinical use include substrates of DOPA (L-3,4-dihydroxyphenylalanine) decarboxylase and substrates of the norepinephrine transporter. A relatively novel development includes ligands for glucagon like peptide 1 (GLP-1) receptor which is overexpressed in high density by benign insulinomas. SSTR2 ligands are also used for therapy of neuroendocrine tumors. Large clinical series have shown that SSTR2 ligands labeled with beta emitters can induce significant and long-lasting objective responses rates in patients with pancreatic NETs, but also in carcinoids of the small intestine. Conclusions: Radiopeptides are effective for the diagnosis and therapy of NETs. When selecting patients for radiopeptide therapy the potential side effects, particularly nephrotoxicity should be considered.