Three-year follow up of adrenal incidentalomas in a New Zealand centre

The international guidelines for management of adrenal incidentalomas (AI) are becoming more conservative. These changes are based on the growing body of evidence suggesting that non-functioning adenomas have a low likelihood of becoming functional or malignant over time.

To follow up at least 100 patients for 3 years who were originally found to have benign adrenal adenomas which were non-functional or had subclinical Cushing syndrome (SCS).

This study prospectively evaluated consecutive patients aged 18 years or older with benign adrenal incidentalomas (AI), not treated with adrenalectomy, which were non-functioning or had SCS. The initial and follow-up evaluation, including clinical assessment, hormonal investigations and imaging were coordinated via a standardised nurse-led AI clinic.

Of 233 patients referred to the AI clinic, 101 patients met the inclusion criteria and completed 3-year follow up. Most of those excluded were due to incomplete initial or follow-up evaluation or were not true AI. Most AI either remained stable or decreased in size on repeat imaging, while 5% of patients had AI enlargement of >5 mm diameter. No patient developed features suggesting adrenal carcinoma. Ninety-two patients had an initial diagnosis of non-functioning adenoma and nine patients had SCS. After 3 years (range 2.9-4.7 years), five of the nine patients with SCS showed normalisation of cortisol parameters (44%), and five of the 92 non-functional AI patients developed SCS (5%).

After 3 years of follow up, approximately half of patients with SCS normalised, while 5% of patients with initially non-functioning adenomas developed biochemical evidence of SCS. This study found a low likelihood of progressive hormonal excess with no evidence of malignancy developing on follow-up evaluation, providing support for the shift towards the more conservative approach to management of AI recommended in recent guidelines.