Evaluation of adenoma size and cortisol secretion status in patients with adrenal incidentalomas at long-term follow-up

Context Increased prevalence of adrenal incidentalomas (AIN) necessitates clarification of optimal follow-up for benign adrenal adenomas without overt hormone excess. Aim: To evaluate the radiological and hormonal assessment of AIN patients to determine the risk of malignant transformation, development of overt hormone excess or mild autonomous cortisol secretion (MACS) during long-term follow-up. Materials and Methods: Retrospective cohort study. In a total number of 908 AIN patients, eligible 467 patients with adrenal adenomas were enrolled. Results: Median age was 55 (21-85) years with a female dominance (73.4%). Median adenoma size was 20 (10-65) mm. Median follow-up duration was 60 (12-204) months. Increase in adenoma size was observed in 36.8% and significant increase (≥10mm) was observed in 4.7% of the patients. Development of overt hormone secretion or adrenocortical carcinoma was not detected while 13 patients with NFA (3.9% of NFA) transformed to MACS and 3 patients with MACS (10.2% of MACS) transformed to NFA at follow-up. Among 13 patients transformed from NFA to MACS, 39% featured ≥10mm increase in adenoma size while this was 4% in patients with stable cortisol secretion level during follow-up (p<.001). Transforming from NFA to MACS at follow-up was the strongest independent predictor of an increase ≥10mm in size in multivariate analysis Beta: 2.352, OR(CI%): 10.5- (2.8-39.2), p< .001. Conclusion: Incidentally discovered adrenal adenomas feature a stable course in terms of adenoma size and hormonal status. However, given our findings demonstrating an interrelation between adenoma enlargement and MACS development, follow-up radiological and hormonal work-up should be individualized.