Diagnostic efficacy of 18F-FDG PET/CT in patients with adrenal incidentaloma

Abstract

Background The management of adrenal incidentaloma is still a challenge with respect to determining its functionality (hormone secretion) and malignancy. In this light, we performed 18F-FDG PET/CT scan to assess the SUVmax values in different adrenal masses including Cushing syndrome, pheochromocytoma, primary hyperaldosteronism and non-functional adrenal adenomas. Methods Total 109 (73 F, 36 M) patients with adrenal mass (incidentaloma), mean age of 53.3 ± 10.2 years (range, 24–70) were screened by 18F-FDG PET/CT. Data of 18F-FDG PET/CT imaging of the patients were assessed by the same specialist. Adrenal masses were identified according to the calculated standardized uptake values (SUVs). Clinical examination, 24-h urine cortisol, catecholamine metabolites, 1-mg dexamethasone suppression test, aldosterone/renin ratio and serum electrolytes were analyzed. Results Based on the clinical and hormonal evaluations, there were 100 patients with non-functional adrenal mass, four with cortisol-secreting, four with pheochromocytomas and one with aldosterone-secreting adenoma. Mean adrenal mass diameter of 109 patients was 2.1 ± 4.3 (range, 1–6.5 cm). The 18F-FDG PET/CT imaging of the patients revealed that lower SUVmax values were found in non-functional adrenal masses (SUVmax 3.2) when compared to the functional adrenal masses including four with cortisol-secreting adenoma (SUVmax 10.1); four with pheochromcytoma (SUVmax 8.7) and one with aldosterone-secreting adenomas (SUVmax 3.30). Cortisol-secreting (Cushing syndrome) adrenal masses showed the highest SUVmax value (10.1), and a cut-off SUVmax of 4.135 was found with an 84.6% sensitivity and 75.6% specificity cortisol-secreting adrenal adenoma. Conclusions Consistent with the similar studies, non-functional adrenal adenomas typically do not show increased FDG uptake and a certain form of functional adenoma could present various FDG uptake in FDG PET/CT. Especially functional adrenal adenomas (cortisol secreting was the highest) showed increased FDG uptake in comparison to the non-functional adrenal masses. Therefore, setting a specific SUVmax value in the differentiation of malignant adrenal lesion from the benign one is risky and further studies, including a high number of functional adrenal mass are needed.

Management of adrenocortical carcinoma in Western Australia: a perspective over 14 years

“…PET‐CT is advocated as a useful tool in differentiating malignant and benign adrenal lesions with a reported SUV max criteria of 2.3–4.04 and tumour SUVmax:liver SUVmax ratios >1.5 21–25 . A pitfall is functional adenomas, however, where higher SUVmax values have been reported, particularly with cortisol producing adenomas 26,27 . The majority of patients in our series with a pre‐operative PET‐CT scan (91%) had high SUV rates.…”

“…[21][22][23][24][25] A pitfall is functional adenomas, however, where higher SUVmax values have been reported, particularly with cortisol producing adenomas. 26,27 The majority of patients in our series with a pre-operative PET-CT scan (91%) had high SUV rates.…”

Neoplastic metastases to the endocrine glands

“…However, setting a specific SUVmax value in the differentiation of malignant from benign adrenal lesions may be risky (Akkus et al 2019). Table 2 shows the main characteristics of a benign adrenal tumour versus an adrenal metastasis on CT, MRI and 18 FDG-PET-CT.…”

The Potential of Steroid Profiling by Mass Spectrometry in the Management of Adrenocortical Carcinoma

“…Conversely, lipid-poor lesions, as metastases, pheochromocytomas, or ACC, do not show any change in signal intensity on out-of-phase images [8]. FDG-PET and/or PET/CT is widely used to characterize indeterminate adrenal lesions or lesions suspected of malignancy at first line imaging [21] and to assess recurrence during the follow up of ACC patients. Non-functional adrenal adenomas typically do not show increased FDG uptake and a certain form of functional adenoma (especially cortisol secreting) could present various FDG uptake.…”