Purpose: To compare long-term outcomes in patients with adrenal incidentalomas (AIs) with the response to a 1 mg overnight dexamethasone suppression test (DST).
Methods: Consecutive patients with "non-functional" AIs (n = 365) were examined. Patients with overt hormone excess, adrenocortical cancer and known malignancy had been excluded. Patients were classified to normal cortisol secretion group (n = 204, DST ≤ 50 nmol/l), possible autonomous cortisol secretion group (n = 128, DST 51-138 nmol/l) and autonomous cortisol secretion group (n = 33, DST ≥ 138 nmol/l).
Results: Thirty-seven patients (10.1%) deceased during the follow-up period (5.2 ± 2.3 years): 16(7.8%) in the non-secreting group (time from diagnosis to death: 3.9 ± 2.9 years), 15 in the possible autonomous cortisol secretion group (11.7%, 3.2 ± 1.8 years) and 6 in the autonomous cortisol secretion group (18.2%, 2.3 ± 1.5 years), respectively (P = 0.019). Multivariate analysis only found significant association with age and the tumour size but if cortisol levels post-DST were analysed as a continuous variable it was significant as well. All deaths in autonomous cortisol secretion group were due to cancer not related to adrenal glands. Hypertension, cardiovascular disease and medications were more common in the possible and autonomous cortisol secretion group, especially in the former. More bilateral AIs and larger AI size were found in the two latter groups.
Conclusions: Patients with autonomous cortisol secretion had higher mortality than those with non-functioning AIs though cortisol levels post-DST as a continuous variable, age and tumour size were better predictor of mortality. Cardiovascular disease and osteoporosis medication seemed more prevalent in the possible and autonomous cortisol secretion groups, especially in the former.
Keywords: Autonomous cortisol secretion; Cancer; Dexamethasone suppression test; Mortality; Prognosis; Subclinical Cushing’s syndrome.