Trial Information

Ga68-DOTA-NOC-PET Imaging of Neuroendocrine Tumors

Neuroendocrine tumors (NETs), best treated by complete surgical resection, are frequently
difficult to localize due to small size, presence in hollow organs, and morphological
changes caused by prior surgery. Imaging of NETs relies primarily on conventional
morphological methods (EUS, CT, MRI, US). Functional imaging, such as somatostatin receptor
scintigraphy (SRS) using the In111-labeled somatostatin analog octreotide, provides better
staging of the disease, visualization of occult tumor, and evaluation of patient eligibility
for somatostatin analog treatment. This modality is effective for carcinoid tumors, and for
most pancreatic islet-cell tumors. However, it may fail to detect some tumors, mostly due to
low density of somatostatin receptors, with resulting lack of tumor uptake. The relatively
poor spatial resolution of planar and SPECT imaging may also reduce tumor detection,
particularly for small tumors and/or those with low uptake. Furthermore, this technique is
lengthy, often requiring repeated imaging over 24-48 hours. Introduction of newer
somatostatin analogs such as DOTANOC offers many advantages. Higher uptake of the newer
analogs in more of the somatostatin receptor subtypes improves lesion detection. In
addition, labeling with the positron emitter, Ga68, instead of In111 improves the
pharmacokinetics of the tracer, and the faster tumor uptake and more rapid clearance from
normal tissues increases tumor to background contrast, improving tumor visualization, and
resulting in an easier procedure with imaging only 1-2 hours after tracer injection. The
superior spatial resolution of positron emission tomography (PET) again enhances lesion
detectability, and use of PET makes it possible to perform exact quantitation of tracer
uptake that can be useful for monitoring therapy and for planning peptide receptor
radionuclide therapy.

In this study, we propose to use Ga68-DOTANOC PET for imaging of various NETs, comparing the
imaging data to those of anatomical and other functional modalities, and to histopathology,
when available.