Nuclear Medicine Imaging in Neuroendocrine Tumors

Nuclear medicine imaging is key in the initial diagnostic workup and used for staging and re-staging. In addition, it forms basis for planning of therapy targeting somatostatin receptors, either as somatostatin analogs or PRRT. For decades, somatostatin receptor scintigraphy was been performed successfully using a gamma camera technique and SPECT with the tracer 111In-DTPA-octreotide. However, recently, several PET tracers targeting the somatostatin receptors have been introduced and become standard-of-care in many centers. The most commonly used of these are 68Ga-DOTATATE, 68Ga-DOTATOC, and 68Ga-DOTANOC of which the first two have obtained marketing authorizations. They all perform superior to SPECT and should replace gamma camera tracers whenever possible. In addition, 64Cu-labeled PET tracers for somatostatin receptor imaging, for example, 64Cu-DOTATATE, are also gaining momentum and 64Cu-DOTATATE was approved by the FDA on September 2020. With FDG-PET, it is possible to detect a large proportion of the somatostatin receptor negative cases and FDG-PET therefore seems to be a valuable addition. Furthermore, FDG-PET has prognostic information that potentially be used in selection of therapy. With the above-mentioned PET tracers available, the need for 123I-MIBG, 18F-DOPA, and 11C-5-HTP seems to be limited.