Functional Oncological Imaging of the Endocrine System

Abstract

Endocrine tumors are hormonally active benign or malignant neoplasms arising within endocrine organs or from specialized cells of the amine precursor uptake and decarboxylation (APUD) system that are increasing in incidence as a result of sensitive biochemical tests and high-resolution diagnostic imaging. Not unlike tumors of other systems, endocrine neoplasms are heterogenous with variable prognosis characterized by well-differentiated thyroid cancer with very favorable outcome, medullary thyroid cancer and neuroendocrine-type tumors with intermediate outcomes, and anaplastic thyroid, adrenocortical, and Merkel cell cancers with the poorest clinical outcomes. Medical imaging has become a key component in diagnosis and staging of endocrine malignancies; however, even with great advances in computed tomography and magnetic resonance imaging, detection of small primary tumors and metastases continues to be a challenge. Complimentary functional imaging targets tumor cellular processes that actively accumulate radiopharmaceuticals, allowing sensitive and highly specific oncological imaging. Surveillance of endocrine malignancies commonly combines functional imaging with tumor-specific laboratory biomarkers. Furthermore, functional imaging studies can predict efficacy of radionuclide or receptor-based therapies. The last decade has seen an increasing use of combined PET-CT and SPECT-CT scanners designed to create functional and anatomic maps with resultant incremental diagnostic capabilities. These technologies together with the development of novel PET and SPECT radiopharmaceuticals make patient-individualized functional imaging protocols possible, based on the histological grade, degree of differentiation, and genetic profile of their endocrine neoplasm.