Савремена нуклеарномедицинска дијагностика неуроендокриних тумора

Abstract

The new positron emission tomography (PET/CT) methods for neuroendocrine tumors detection are presented and compared with classic, conventional methods. Conventional methods use a gamma scintillation camera for patients with neuroendocrine tumor imaging, after intravenous injection of one of the following radiopharmaceuticals: 1) somatostatin analogues labeled with indium-111 (¹¹¹In-pentetreotide) or technetium-99m (⁹⁹ᵐTc-EDDA/HYNIC-TOC); 2) noradrenaline analogue labeled with iodine-131 or -123 (¹³¹I/¹²³I-MIBG); or 3) ⁹⁹ᵐTc(V)-DMSA. Contemporary methods use PET/CT equipment for patients with neuroendocrine tumor imaging, after intravenous injection of pharmaceuticals labeled with positron emitters [fluorine-18 (¹⁸F), galium-68 (⁶⁸Ga), or carbon-11 (11C)]: 1) glucose analogue (¹⁸FDG); 2) somatostatin analogue (⁶⁸Ga-DOTATOC/⁶⁸Ga-DOTATATE/⁶⁸Ga-DOTANOC); 3) aminoacid precursors of bioamines: [a) dopamine precursor ¹⁸F-DOPA (6-¹⁸F-dihydroxyphenylalanine), b) serotonin precursor ¹¹C-5HTP (¹¹C-5-hydroxytryptophan)]; or 4) dopamine analogue ¹⁸F-DA (6-¹⁸F-fluorodopamine). Conventional and contemporary (PET/ CT) somatostatin receptor detection showed identical high specificity (92%), but conventional had very low sensitivity (52%) compared to PET/CT (97%). It means that almost every second neuroendocrine tumor detected by contemporary method cannot be discovered using conventional (classic) method. In metastatic pheochromocytoma detection contemporary (PET/ CT) methods (¹⁸F-DOPA and ¹⁸F-DA) have higher sensitivity than conventional (¹³¹I/¹²³I-MIBG). In medullary thyroid carcinoma diagnostics contemporary method (¹⁸F-DOPA) is more sensitive than conventional ⁹⁹ᵐTc(V)-DMSA method, and is similar to ¹⁸FDG, computed tomography and magnetic resonance. In carcinoid detection contemporary method (¹⁸F-DOPA) shows similar results with contemporary somatostatin receptor detection, while for gastroenteropancreatic neuroendocrine tumors it is worse. To conclude, contemporary (PET/CT) methods for somatostatin receptor detection (⁶⁸Ga-DOTATOC/-NOC/-TATE) in neuroendocrine tumors are much more sensitive (almost twice) and more accurate than conventional. Therefore the classical methods should be urgently replaced by contemporary methods.

Keywords: neuroendocrine tumors; ⁶⁸Ga-DOTATOC; ¹⁸F-DOPA; 18FDG; 6-18F-fluorodopamine; 11C-5-hydroxytryptophan