SAT-127 Localization and Treatment of the Ectopic ACTH Syndrome Using Somatostatin Analogues

Ectopic ACTH syndrome (EAS) is a rare disorder with a high morbidity and mortality due to the sequelae of severe hypercortisolism and possible underlying carcinoma. It is caused by various tumors, some originating from neuroendocrine cells. Optimal management includes localization and removal of the ectopic ACTH source. About 80% of these tumors have somatostatin (SS) receptors, so that SS analogues may be useful in the localization and treatment. This case demonstrates the use of SS analogues in localization and treatment of EAS. A 49-year-old female presented with 7 months of worsening Cushingoid features including rounded plethoric face, full supraclavicular fat pads, facial hair growth, multiple bruises, violaceous abdominal striae, kyphoscoliosis, 4+ peripheral edema, weight gain, hypertension (190/110 mmHg) and thoracic compression fractures. AM plasma ACTH concentration was 333 pg/mL (nl = 6 - 58 pg/mL); serum concentration cortisol was 71.4 mcg/dL (nl = 7 - 23 mcg/dL) and serum potassium concentration was 1.2 mmol/L (nl = 3.6 - 5.1 mmol/L). A 24-hour urine cortisol could not accurately be obtained. High dose 8 mg overnight dexamethasone testing demonstrated suppression of serum cortisol concentration from 71.4 to 6.3 mcg/dL, suggesting pituitary Cushing disease. Pituitary MRI scan revealed a 2.5 mm disc shaped cystic focus suggesting a Rathke’s cleft cyst. No central-to-peripheral ACTH gradient was present on bilateral inferior petrosal sinus sampling suggesting an ectopic ACTH source. There was a 1.2 x 1.0 cm nodule in the left lower lung lobe on CT chest. A gallium-68 dotatate PET/CT scan demonstrated enhancement of this same lung lesion and mild uptake in the left inferior hilum, suggesting a neuroendocrine lung tumor with possible metastases to lymph nodes. Biopsy and resection of the lesion was deferred until after control of her hypercortisolism. 30mg of Sandostatin LAR was started every 4 weeks to control the ectopic ACTH secretion and to confirm that the SS analogue positive lung lesion was the cause of the EAS. Sandsostatin LAR therapy over the next 12 weeks resulted in a steady clinical and biochemical improvement with a decrease in serum cortisol to 9.7 mcg/dL, control of hypertension (108/64 mmHg), weight loss of 6 pounds, and resolution of supraclavicular fat pads, hypokalemia, and peripheral edema. This confirmed our impression that the neuroendocrine lung tumor was the ACTH source. In summary, this patient with EAS had severe clinical manifestations of hypercortisolism and could not safely undergo surgical intervention. This case demonstrates the value of SS analogues (gallium-68 dotatate PET/CT and Sandostatin LAR) in localizing and confirming the source of ectopic ACTH production and markedly improving the clinical and biochemical features of the EAS.