New Imaging Techniques in the Evaluation of Patients With Ectopic Cushing Syndrome

Between 10 percent and 20 percent of patients with hypercortisolism (Cushing syndrome) have ectopic production of adrenocorticotropin hormone (ACTH) that causes cortisol excess. In approximately 50 percent of these patients, the source of ACTH cannot be found despite very detailed and extensive examination including imaging studies such as computed tomography scanning, magnetic resonance imaging, and octreotide scan (octreoscan) using the conventional low dose of indium-111 pentetreotide. The sensitivity and specificity of these imaging studies depends on anatomic alterations and/or the dose and adequate uptake of radiopharmaceutical. In contrast, positron emission tomography (PET) has the ability to detect pathologic tissue based on physiologic and biochemical processes within the abnormal tissue. This protocol tests whether fluorine-18 dihydroxyphenylalanine (F-DOPA) or use of a higher dose of indium-111 pentetreotide (Octreoscan) can be used to localize successfully the source of ectopic ACTH production. In addition the study examines whether administration of the glucocorticoid antagonist mifepristone can improved the sensitivity of the standard dose Octreoscan. Eligible patients participating in this arm of the study will have a second standard dose scan. Others will receive a higher dose octreoscan instead.

• INCLUSION CRITERIA:

All eligible patients are invited to participate in this protocol. Patients are adults with possible ectopic Cushing syndrome. Since both men and women are affected with ectopic Cushing syndrome, both sexes are studied. All ethnic and racial groups are at risk and will be included. Patients must be willing to return to the National Institutes of Health (NIH) Clinical Center for follow-up studies.

Exclusion criteria

Pregnant or lactating women. A pregnancy test is performed in women of childbearing potential (up to age 55) unless they have a history of hysterectomy.

Children (age less than18) are excluded. Because ectopic ACTH secretion is rare in this age group, the likelihood of benefit is less and does not balance the risk of radiation.

Patients taking medications that alter CYP3A4 activity will not be eligible for the mifepristone study, since this P450 system metabolizes mifepristone. Such participants would receive a clinical high dose (18 mCi) octreoscan (H-OCT) instead, if the standard 6 mCi octreoscan (L-OCT) was negative. Patients with hypokalemia (K < 3.5 milliequivalent (mEq)/L) despite medical therapy with replacement or mineralocorticoid antagonists will also be excluded from the mifepristone studies.

The presence of:

• severe active infection.
• clinically significantly impaired cardiovascular (e.g., history of abnormally low ejection fraction, the presence of moderate pulmonary fluid overload or leg edema, and blood pressure over 190/100), abnormal coagulation (partial thromboplastin time or prothrombin time elevated by 30 percent above the normal values), hematopoietic (hematocrit less than 30 percent, hemoglobin below 10 g/dl, white count below 3000 K/microliter (UL), and platelets below 100,000 K/mm(3)), hepatic (liver enzymes elevated by 3-fold above normal values) or renal function (plasma creatinine level over 2.0).
• impaired mental capacity or markedly abnormal psychiatric evaluation that precludes informed consent.
• body weight over 136 kg, which is the limit for the tables used in the scanning areas.
• combined blood withdrawal, during the six weeks preceding the study, of greater than 450 ml.
• known allergy to 111-indium pentetreotide or other somatostatin analogues.
• strong evidence for Cushing disease. This includes those with positive inferior petrosal sinus sampling or a lesion on pituitary MRI.