Dexamethasone-related adrenal insufficiency in patients with brain and skull base tumours.

PURPOSE: This study aimed to evaluate the prevalence of glucocorticoid-induced adrenal insufficiency in a cohort of patients with brain and skull base tumours and to identify factors which may predict its occurrence.

METHODS: Patients with brain or skull base tumours attending for a short synacthen test (SST) (adrenocorticotropin hormone (ACTH) stimulation test) at a single institution over a 3-year period were retrospectively identified. Baseline demographics and dexamethasone exposure were examined. Only patients with dexamethasone exposure were included in the final analysis looking at the primary end point of SST failure. Fisher's exact test, Student's t test, Mann-Whitney test and the Kendall's tau-b test were used to evaluate the influence of age, gender, diagnosis and mean pituitary radiation dose on the primary endpoint. Receiver operating characteristic (ROC) curves were generated to explore the impact of duration and total exposure to dexamethasone on likelihood of SST failure.

RESULTS: Thirty-one of 51 patients with previous dexamethasone exposure failed their first SST (61%). No significant relationship was demonstrated between age, gender, diagnosis or mean pituitary radiation dose and SST failure. Duration of and total exposure to dexamethasone were significantly associated with SST failure (p = 0.001 and p = 0.007, respectively). ROC curves generated values of 78 days and 171 mg days to give a sensitivity of 94 and 97%, respectively, to detect SST failure.

CONCLUSIONS: Duration of dexamethasone use and total exposure predict for adrenal insufficiency in patients with brain and skull base tumours. Values derived from this study may be useful to identify patients at higher risk of adrenal suppression who require empirical hydrocortisone pending formal testing of the hypothalamic-pituitary-adrenal axis.