Imaging techniques can be used to determine the location of the primary tumor and evaluate tumor extent (localization and metastases). The optimum imaging technique depends on whether it is detecting disease in a patient with a suspected NET or assessing the extent of disease in a known case. Common imaging techniques include computed tomography (CT) or MRI scans, which can be used to identify different NETs. Table 1 summarizes the sensitivities of various imaging techniques for locating specific NETs. It is worth mentioning that both CT and MRI have significantly improved the sensitivity and specificity (~90%) using new techniques and contrast media. Somatostatin-receptor scintigraphy (SRS; Octreoscan®, Mallinckrodt, Petten, The Netherlands) is performed by injecting a small amount of a radioisotope such as (111In-DTPA0) octreotide (111In-pentetreotide) or (111In-DOTA0) lanreotide, which then binds with high affinity to the two most prevalent somatostatin receptors found on NETs (sst2 and sst5); this allows visual evidence of NET localization. SRS is indicated as the first staging procedure and is the most sensitive single-screening method for extrahepatic disease manifestation. Whole-body imaging enables the identification of distant metastases and, therefore, SRS is the diagnostic test of choice for locating secondaries. PET-scanning with 68Gallium-DOTATOC, although currently only available at specialized centers, may replace SRS in the future as it has higher sensitivity and is easier to perform. Positron emission tomography scans may be used to complement information gathered from physical examination, CT, SRS and MRI scans. There are specific tracers for NETs such as 11C-5HTP, 11C-Dopa and 18F-Dopa that have demonstrated high sensitivity and specificity.
Expert Rev Endocrinol Metab. 2011;6(1):49-62. © 2011 Expert Reviews Ltd.
Cite this: Management of Neuroendocrine Tumors: Current and Future Therapies - Medscape - Jan 01, 2011.