Update on nuclear medicine imaging of neuroendocrine tumors.

Radiolabeled tracers provide a functional imaging technique to identify neuroendocrine tumors, usually with greater sensitivity and specificity than anatomic imaging techniques such as computed tomography (CT), magnetic resonance imaging and ultrasound. Currently, there are several single-photon techniques available using either (123)I-MIBG, (111)In-DTPA-pentetreotide (Octreoscan) or (99m)Tc-EDDA/HYNIC-tyr3-octreotate. (111)In-DTPA-pentetreotide is most widely used. The best results are achieved with single-photon emission computed tomography/CT. Positron emission tomography (PET) and PET/CT are likely to provide further improvements in tumor detection, but there is, at the present time, no consensus on the choice of tracer. (18)F-FDG, (68)Ga-DOTA-TOC and (68)Ga-DOTA-NOC, (18)F-FP-Gluc-TOCA, (18)F-FDOPA and (11)C-5HTP (hydroxy tryptophan) are currently being evaluated. Early results and issues pertaining to availability are reviewed. The identification of the 'best' tracer will depend on multiple factors.