Prospective Evaluation of 68Ga-DOTATATE PET/CT, Octreotide and F-DOPA PET Imaging in Ectopic Cushing Syndrome

Study Description: Between 10% and 15% of patients with endogenous hypercortisolism (Cushing syndrome) have ectopic (non-pituitary) production of adrenocorticotropin hormone (ACTH) that causes cortisol excess. In approximately 50% of these patients, the tumoral source of ACTH cannot be found initially despite very detailed and extensive imaging, including studies such as computed tomography, magnetic resonance imaging, and octreotide scan (Octreoscan) using the standard dose of indium- 111 pentetreotide (\[111In-DTPA-D-Phe\]-pentetreotide). The sensitivity and specificity of structurally based imaging studies depends on anatomic alterations and the size of the tumor. In contrast, positron emission tomography (PET) and somatostatin ligand imaging detect pathologic tissue based on physiologic and biochemical processes within the abnormal tissue. This protocol tests the ability of \[18F\]-L-3,4-dihydroxyphenylalanine (18F-DOPA) PET, and the somatostatin imaging analogue, 68Ga-DOTATATE-PET, to localize the source of ectopic ACTH production. Objectives: Primary Objectives: * To determine which imaging technique (F-DOPA PET/CT, 68Ga-DOTATATE PET/CT, standard CT, and/or standard MRI) has the best sensitivity. * To determine if there is a combination of imaging tests with optimal diagnostic accuracy. Secondary Objective: -To evaluate a potential correlation between 18F-DOPA or 68Ga-DOTATATE uptake and the type of tumor, its size, SSTR expression or proliferative activity. Exploratory Objectives: * To evaluate the ability of gated cardiac imaging with CT and MRI to improve the detection of retrocardiac lung lesions. * To determine whether PET scans at an interval of less than one year localize tumors. Endpoints: Primary Endpoint: -Imaging results and pathology of resected tumors Secondary Endpoints: -18F-DOPA or 68Ga-DOTATATE imaging results, tumor pathology, tumor size, proliferative index and SSTR expression. Exploratory Endpoints: * Gated cardiac imaging CT and/or MRI; all other imaging results, tumor pathology. * Imaging results and pathology of resected tumors.