New trends in diagnosis and localization of (neuro)endocrine tumors
Endocrine tumors differ from other tumors in that that they use specific pathways to synthesize, store, and release hormones, their metabolites, or precursors; these tumors may differentially express specific receptors or transporters located in either the cell membrane or intracellular space. Additionally, they can uptake released hormones back into their cells. These characteristics allow for the existence of several (neuro)endocrine, tumor-specific markers that can be used to diagnose these tumors. These markers can also be used to monitor progression, recurrence, and/or therapeutic responses to various treatment modalities.
Whereas anatomical imaging modalities may well define the size, shape, and structure of tumors, they lack the ability to explore their functional characteristics. Various functional imaging methods exist, of which positron emission tomography (PET) is becoming most popular, in part due to its use in a clinical as well as experimental procedures. One of the advantages of PET scanning is the ability to measure tumor characteristics in vivo, including such processes as glucose and energy metabolism, DNA and protein synthesis, angiogenesis, apoptosis, and blood flow, among others. Thus, PET in endocrine oncology provides specific tumor detection (in vivo histology); identifies of specific tumor function and targets for therapy; predicts and assesses responses to therapy regardless of size changes (early tumor response); determines the prognosis even before metastatic lesions occur; and eliminates unnecessary treatments, if, for example, a target molecule is not found. The use of PET/CT has dramatically improved detection, localization, and characterization of various tumors, including (neuro)endocrine ones. The emerging technology of PET coupled with MRI is on the horizon and will revolutionize how we study the molecular and functional aspects of tumors.
The most updated use of diagnostic markers as well as functional imaging in the evaluation of (neuro)endocrine tumors and clinical approaches on how to use them for optimal tumor assessment will be presented. Finally, future trends in functional imaging, including its use in pharmacodynamics and molecular imaging tightly linked to individualized medicine to secure the optimal therapeutic plan, will also be outlined.
Acknowledgements: This research was supported by the Intramural Research Program of the NICHD/NIH.