Highlight
Ectopic Cushing syndrome (ECS) presents frequently with severe hypercortisolism and high rates of metastatic disease.
Early achievement of complete biochemical remission within six months markedly reduces the risk of complications and Cushing syndrome-related mortality.
Failure to control hypercortisolism early identifies ECS as an endocrine emergency requiring timely intervention.
Despite aggressive management, overall mortality remains high in patients with ECS, underscoring the need for advances in diagnosis and treatment.
Study Background and Disease Burden
Ectopic Cushing syndrome (ECS) is a rare but severe endocrine disorder characterized by excess production of adrenocorticotropic hormone (ACTH) by non-pituitary tumors, leading to hypercortisolism. Unlike pituitary-dependent Cushing disease, ECS often involves non-metastatic or metastatic neuroendocrine tumors producing ACTH ectopically. The hypercortisolemia can cause profound metabolic derangements, immunosuppression, and morbidity, complicating management and impairing survival. Due to its rarity and heterogeneity, data on long-term outcomes, optimal treatment strategies, and determinants of mortality remain limited. This international, multicentre retrospective cohort study addresses this gap by providing comprehensive real-world data from endocrinology referral centres spanning multiple continents, elucidating factors that influence prognosis and complications in ECS.
Study Design
This study involved 49 high-volume endocrine referral centres across Asia, Europe, North America, South America, and New Zealand. It retrospectively enrolled 1463 patients with a clinical diagnosis of ECS, confirmed by expert adjudication at individual sites based on multiple diagnostic criteria, including inferior petrosal sinus sampling, dynamic endocrine testing, remission post-tumor-directed therapy, or radiological evidence of tumor source. The cohort included patients diagnosed across a wide age spectrum (3–87 years) with a median age of 51 years. Data collection occurred between May 2024 and April 2025, and patients were followed for a median of 57 months to assess clinical features, biochemical severity, interventions (surgical excision, radiotherapy, cryoablation), complications, and mortality.
The primary endpoint was adjudicated Cushing syndrome-related mortality. Secondary outcomes included overall mortality and incidence of complications such as infections, thromboembolism, and cardiovascular and cerebrovascular events. The study also analyzed outcomes stratified by achievement of biochemical remission and timing relative to diagnosis using landmark analyses to differentiate early (within 6 months) versus late outcomes.
Key Findings
This cohort demonstrated a predominance of severe disease at presentation: 91.1% exhibited severe hypercortisolism and 79.4% hypokalemia, with 57.1% harboring metastatic tumors. The sex distribution showed a slight female predominance (56.3%), and the majority (69.8%) were of White race.
Complications were frequent and severe. Infection affected nearly one-third of patients (31.7%), venous thromboembolism in 8.5%, cardiovascular events in 6.4%, and cerebrovascular events in 2.5%. Mortality was substantial: 13.4% died from ECS-related causes, and overall mortality reached 42.8%. These data underscore the critical systemic burden and early mortality risk associated with ECS.
Crucially, achieving complete biochemical remission of hypercortisolism within six months of diagnosis significantly reduced risk of late complications and Cushing syndrome-related death. Specifically, the adjusted hazard ratio for late complications was 0.55 (95% CI 0.38–0.80), and for Cushing syndrome-related mortality was 0.49 (95% CI 0.27–0.89). Notably, remission did not significantly affect non-Cushing syndrome-related mortality, emphasizing the direct impact of cortisol excess control on ECS-specific outcomes.
The landmark analysis revealed that early biochemical control constitutes a pivotal therapeutic window; failure to normalize cortisol levels by six months predicted markedly poorer prognosis. This finding establishes ECS as a medical emergency necessitating prompt multidisciplinary treatment to achieve remission.
Expert Commentary
This extensive international cohort represents the largest and most geographically diversified ECS study to date, bringing valuable real-world insights to a rare endocrine condition. The strong association between early biochemical remission and improved outcomes is biologically plausible given cortisol’s immunosuppressive, pro-thrombotic, and catabolic effects.
The results highlight an urgent need for early identification and aggressive management of ECS, including biochemical monitoring and prompt tumor localization and treatment. Although the study is retrospective, the rigorous patient adjudication and large sample provide robust and generalizable evidence. Limitations include potential referral bias typical of high-volume centers and heterogeneity in treatment modalities.
Future studies should explore optimized protocols for early tumor detection, minimally invasive therapies, and adjunctive medical treatments to control hypercortisolism. The high complication and mortality rates despite current management also call for innovation in systemic therapies and supportive care.
Conclusion
Ectopic Cushing syndrome is a critical endocrine emergency characterized by severe hypercortisolism, high morbidity, and mortality. This international multicentre study demonstrates that achievement of complete biochemical remission within six months is essential to reduce late complications and Cushing syndrome-related mortality. The findings underscore the importance of rapid diagnosis, effective tumor-directed interventions, and cortisol control in improving outcomes. ECS management should be prioritized as time-sensitive, mandating multidisciplinary collaboration and vigilance for complications. Continued research is needed to refine therapeutic strategies and enhance survival in this challenging condition.
Funding and Clinical Trial Registry
This study was funded by the Mayo Clinic. As a retrospective cohort study, no clinical trial registration applies.
References
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