MON-011 Presentation, Management and Outcomes of Ectopic ACTH Syndrome: an International Multicenter Retrospective Study

Abstract Disclosure: S.R. Chacko: None. C.A. Villavicencio Torres: None. K. Yu: None. S.G. Waguespack: None. L. Lu: None. Z. Belaya: None. T. Bandgar: None. A. Sada: None. O. Ragnarsson: None. B. Altieri: None. A. Newman: None. P. Vibhatavata: None. M. Tóth: None. E.V. Varlamov: None. C. Badiu: None. A. Paissan: None. M. St-Jean: None. H. Falhammar: None. N. Imamudeen: None. L. Haberbosch: None. M. Bobrowicz: None. A. Tabarin: None. R. Shah: None. M.R. Gadelha: None. A. Peersen: None. W.F. Young: None. J. Kaplan: None. J. Varghese: None. M.A. Habra: None. O. Golounina: None. G.A. Melnichenko: None. A.R. Lila: None. C. Yamichannaiah: None. I. Bancos: None. Context: Cushing syndrome (CS) due to ectopic ACTH secretion (EAS) is a rare condition, associated with severe hypercortisolism and consequent morbidity and mortality. Its varied and often emergent presentation make diagnosis and treatment challenging. Objectives: 1.Characterize clinical and biochemical presentation of EAS. 2.Describe the scope of hypercortisolism-related complications, overall and CS-specific mortality. 3.Identify factors associated with CS-specific mortality. Methods: We conducted a multicenter retrospective cohort study in patients with EAS at 37 centers. Outcomes were clinical/biochemical severity scores, complications, overall and CS-specific mortality. Results: In 1053 patients [median age at diagnosis 52 years (IQR 37-64), 57% women], metastatic disease was present at diagnosis in 585 (56%). The most common sources of EAS were bronchial neuroendocrine neoplasm (NEN) (304, 29%), pancreatic NEN (114, 11%) and small cell lung carcinoma (114, 11%), with the source of EAS being occult in 192 (18%). Clinical and biochemical severity scores were severe in 475 (45%) and 873 patients (92%) respectively. Hypokalemia was present in 819 patients (78%) in the year prior to diagnosis. Of 342 patients (32%) who had IPSS, 301 (88%) suggested an ectopic source, 7 (2%) a pituitary source, and 23 (7%) were non-diagnostic. Of 595 patients who had both functional and cross-sectional imaging, discordant findings were seen in 122 (21%), concordant lesion was seen on both in 326 (55%), and no lesion in 147 (25%). Of those with discordant results, cross-sectional imaging was accurate in 66 (54%) and functional imaging in 56 (46%).Management included medical therapy alone in 237 (23%), surgical excision of the source of EAS in 158 (15%), bilateral adrenalectomy in 77 (7%) and multimodal therapies in 498 patients (47%). Complications within 5 years after diagnosis included hospitalization related to CS or its therapy in 351 (33%), infection in 337 (32%), thromboembolic event in 102 (10%), cardiovascular event in 83 (8%) and cerebrovascular event in 27 (3%). During a median follow-up of 35 months (IQR 20-122) from CS diagnosis, death occurred in 462 patients (44%), with the cause of death related to CS in 149 (14%). CS-specific mortality was higher in metastatic compared with non-metastatic disease (19% vs. 7%, P<0.001). On multivariable analysis of age, sex, clinical and biochemical severity, older age (HR 1.03, 95% CI: 1.02-1.04) and lower clinical severity score (HR 0.97, 95% CI: 0.94-0.99), were associated with higher CS-specific mortality. Conclusion: Our interim analysis, the largest worldwide, found that most patients with EAS had severe hypercortisolism and hypokalemia. Metastatic disease was present in 56%, and the source of EAS was occult in 18%. CS-related death occurred in 14%, emphasizing the need for urgent management. Presentation: Monday, July 14, 2025