Natural course of adrenal incidentalomas: seven-year follow-up study

Most adrenal incidentalomas are nonfunctioning cortical adenomas that do not require surgery. Operative treatment is indicated if the incidentaloma has malignant features as seen during the radiologic workup, is hormonally active, or grows during follow-up. A conservative attitude is justified in asymptomatic patients if we know that the natural course of these tumors is not disadvantageous. We followed a group of patients treated by observation to determine the natural course of adrenal incidentalomas. Altogether 30 incidentalomas in 27 patients were detected in the Helsinki University Central Hospital from June 1981 through December 1992 and were re-examined during 1997. The patients were evaluated clinically, and hormonal testing was done by performing a 1-mg overnight dexamethasone suppression test; the next day we measured the 24-hour urinary excretion of vanillylmandelic acid, metanephrines and normetanephrines, and serum potassium. Magnetic resonance imaging (MRI) was used to determine the size of the tumor. If the patient had died during the follow-up period, the causes of death from the death certificates and autopsy reports were reviewed. The mean follow-up was 7 years. Nine patients had died, with none of deaths related to the incidentaloma. Sixteen patients were evaluated clinically and by the basic hormonal tests and MRI; none showed any signs of hormonal activity or features of malignancy. Two patients did not want to be reexamined but stated that they were asymptomatic. This follow-up study supports the conclusion that conservative therapy is justified because the growth tendency of adrenal incidentalomas is slow and they seem to remain hormonally inactive.