Endogenous Cushing's syndrome and cancer risk.

Objective: Cancer incidence in patients with endogenous Cushing's syndrome (CS) has never been established. Here, we aimed to assess the cancer risk in patients with CS as compared with individually matched controls.

Design: A nationwide retrospective matched cohort study of patients with endogenous CS diagnosed between 2000 and 2023 using the database of Clalit Health Services in Israel.

Methods: Patients with adrenal carcinoma or ectopic CS were excluded. Patients with CS were matched in a 1:5 ratio, with controls individually matched for age, sex, socioeconomic status, and body mass index. The primary outcome was defined as the first diagnosis of any malignancy following a CS diagnosis. Risk of malignancy was calculated using the Cox proportional hazard model, with death as a competing event.

Results: A total of 609 patients with CS and 3018 controls were included [mean age at diagnosis, 48.0 ± 17.2 years; 2371 (65.4%) women]. The median follow-up was 14.7 years (IQR, 9.9-20.2 years). Patients with CS had an increased cancer risk, with a hazard ratio (HR) of 1.78 (95% CI 1.44-2.20) compared with their matched controls. The risk of malignancy was elevated in patients with Cushing's disease (251 cases and 1246 controls; HR 1.65, 95% CI 1.15-2.36) and in patients with adrenal CS (200 cases and 991 controls; HR 2.36, 95% CI 1.70-3.29). The increased cancer risk in patients with CS persists after exclusion of thyroid malignancies.

Conclusion: Endogenous CS is associated with increased malignancy risk. These findings underscore the need for further research to establish recommendations for cancer screening in this population.