This article provides an update on functional imaging approaches for diagnostic localization of endocrine
tumors, with emphasis on positron emission tomography (PET). [
18F]Fluorodeoxyglucose PET scanning is now a widely accepted imaging approach in clinical oncology. Benefits include improved patient outcome facilitated by staging and monitoring of disease and better treatment planning. [
18F]Fluorodeoxyglucose PET is also useful in some endocrine
tumors, particularly in recurrent or metastatic
thyroid cancer where the degree of accumulation of the
radionuclide has prognostic value. However, this imaging approach does not take full advantage of the unique characteristics of endocrine
tumors. Endocrine
tumor cells take up
hormone precursors, express receptors and transporters, and synthesize, store, and release
hormones. These characteristics offer highly specific targets for PET.
Radiopharmaceuticals developed for such approaches include 6-[18F]fluorodopamine, and [11C]hydroxyephedrine for localization of
pheochromocytomas, [11C]
5-hydroxytryptophan and [11C]L-
dihydroxyphenylalanine for
carcinoid tumors, and [11C]
metomidate for adrenocortical
tumors. These functional imaging approaches are not meant to supplant conventional imaging modalities but should be used conjointly to better identify specific characteristics of endocrine
tumors. This represents a relatively new and evolving approach to imaging that promises to answer specific questions about the behavior and growth of endocrine
tumors, their malignant potential, and responsiveness to different treatment modalities.