Survival probabilities in patients with ectopic Cushing's syndrome-a systematic review and a single-arm meta-analysis

We aimed to estimate 1- and 5-year survival probabilities in patients with different forms of ectopic Cushing's syndrome (ECS) and identify factors influencing survival.

In this systematic review and meta-analysis, we searched the online databases PubMed, Scopus, and Web of Science up to October 18, 2023, for studies reporting survival in patients with ECS. Data extraction and risk of bias assessment were performed by 3 independent investigators. Primary outcome was survival in patients with ECS and secondary outcome was factors influencing survival.

We included 40 studies with a total of 1148 patients. The pooled mean 1-year survival probability for ECS of mixed etiologies was 78% while the mean pooled 5-year survival probability was 47%. The 5-year survival probabilities for patients with pulmonary neuroendocrine neoplasm (NEN) was 81%, occult ECS 66%, thymic NEN 50%, and pancreatic NEN 40%. Only 8 studies reported factors influencing survival, where total resection of the primary tumor was associated with better overall survival, and unresectable tumors, metastatic disease at diagnosis, severe hypercortisolism, hypokalemia, and new-onset diabetes mellitus were associated with worse prognosis.

Survival in ECS varies considerably, mainly due to the underlying origin of the tumor, tumor stage, and severity of the hypercortisolism. Further studies analyzing the importance of factors affecting survival are needed.