New Sparks and Spots: Molecular Imaging with Positron Emission Tomography Will Change Management of Cushing's Disease

Cushing's disease is caused by corticotroph tumors of the pituitary gland, resulting in adrenocorticotropic hormone hypersecretion and cortisol excess. The majority of the tumors are microadenomas. Magnetic resonance imaging (MRI) imaging is able to detect up to 70% of the corticotroph tumors. In the remaining patients, no tumor is detectable on MRI or there are equivocal changes without a clear demarcation of a tumor. Hence, the cure rates following transsphenoidal pituitary surgery are far from being satisfactory, with around 60% to 90% short-term remission in expert centers. Positron emission tomography (PET) has recently emerged as a potent method for the localization of small corticotroph adenomas and corticotroph adenomas without demarcation on the MRI. This review analyzes the radiopharmaceuticals most commonly used in evaluating pituitary disorders and explores the potential utilization of new PET tracers for personalized management of patients with Cushing's disease. Especially 11C-methionine and 18F-fluorethyltyrosine PET have recently been reported to be highly sensitive methods to detect MRI-undetectable corticotropinomas in 80% to 100% of patients. If confirmed in randomized controlled trials, PET imaging could be a major break-through towards targeted, individualized surgical therapy.