Corticosteroid‐associated hypothalamic–pituitary–adrenal axis suppression in brain tumours: a focus on dosing and tapering

Brain tumours are among the most challenging malignancies to treat. The majority of brain tumours are associated with perifocal oedemas and disturbances in the cerebrospinal fluid (CSF) flow. Glucocorticoids (GC) are the mainstay supportive therapy for a variety of disorders associated with brain tumours such as vasogenic oedema, intracranial pressure, headache, and vomiting. In contrast, prolonged exposure to GC has been associated with suppression of the hypothalamic–pituitary–adrenal (HPA) axis. Moreover, abrupt tapering and sudden stopping of GC therapy are the most common causes of HPA axis suppression leading to secondary adrenal insufficiency (SAI). Furthermore, a variety of well‐established dynamic tests have been used to diagnose and assess the integrity of the HPA axis, such as the insulin tolerance test, the metyrapone stimulation test and the adrenocorticotropic hormone stimulation test. Hydrocortisone replacement is the recommended therapy for SAI as it provides the physiological circadian cortisol rhythm. In the context of brain tumours, limited evidence exists to guide clinical practice regarding the optimal dosing of GC with regard to side effects, duration of therapy, withdrawal regimen or quality of life. In this review, we summarise the current status of HPA axis suppression and the SAI associated with GC therapy in brain tumours.