A Case of Ectopic Cushing’s Syndrome From a Large Cell Neuroendocrine Lung Tumor With Small Cell Component/Features

Abstract

Abstract Background: Endogenous Cushing’s syndrome is uncommon in clinical practice. Survival of patients with new onset ectopic Cushing’s syndrome at relapse of small cell lung cancer has been found to be poor, with death occurring within an average of 27.3 days. Case Report: A 61-year-old African American male was seen by endocrinology service for inpatient evaluation of refractory hypokalemia of three months duration requiring recurrent potassium replacement with oral and intravenous therapy. He was inpatient for depressive symptoms and suicidal ideation. His admission lab showed hypokalemia of 2.7 mmol/L associated with elevated serum ACTH and serum cortisol. Past medical history is significant for unresectable large cell neuroendocrine neoplasm of the lung with small cell components/features diagnosed two years prior during lung cancer screening. He received chemotherapy with cisplatin/etoposide at diagnosis. He however had recurrence one year later with distant metastases. He was re-treated with cisplatin/etoposide in addition to palliative radiation therapy to painful bone met in his right hand. Three months prior to admission, imaging showed progression of the cancer with presence of new lesions in the liver for which he received one cycle of Nivolumab monotherapy. Social history was significant for 30-pack year smoking history. Physical exam findings were significant for: elevated blood pressure 167/96 mmHg, tachycardia of 107 bpm, oxygen saturation of 95% on 3-liters of intranasal oxygen, cachexia, absent buffalo hump, absent striae and decreased power in both lower limbs. Lab on supplementation showed serum potassium of 3.6, Serum magnesium of 2.0 and creatinine clearance greater than 60 Serum cortisol was 116.1 (5-25) mcg/dl and ACTH was 268.0 (9-52) pg/ml. An MRI by the referring team did not show a pituitary lesion. Patient was diagnosed with Cushing’s syndrome due to ectopic ACTH-production from a large cell neuroendocrine lung tumor with small cell component/features. Chart review showed his onset of hypokalemia occurred at the same time that imaging showed progression of the tumor three months prior. He was started on Ketoconazole and his cortisol level reduced to 14.0 within forty-eight hours with associated correction and stabilization of hypokalemia. The plan was to “block and replace” cortisol so that oncology could re-start chemotherapy. However, the patient developed acute respiratory decompensation requiring continuous BiPAP. Chest imaging showed progression of lung lesions with post obstructive pneumonia. The patient’s family opted for comfort measures and he was transferred to hospice care where he passed on ten days later. Conclusion: In the setting of lung cancer, new onset paraneoplastic Cushing’s syndrome may have prognostic implications. Clinicians should be aware of this, provide treatment for hypercortisolism and refer early to palliative care.