Diagnostic accuracy of 18F-FDG PET/TC for the characterization of adrenal lesions in a heterogeneous population

Purpose: Data regarding 18F-FDG PET for the characterization of adrenal lesions are limited; to evaluate the performance of the tumour-to-liver maximum standardized uptake values (SUVratio) > 1.5 to predict malignancy. Patients and methods : Retrospective analysis of adrenal lesions undergoing 18F-FDG-PET/CT (2013–2022). Gold standard for benignity was: i) histology; ii) stability or minimal diameter increase (< 20%/ 1.5 and the optimal SUVratio in our population was calculated by ROC curves. Results 42 lesions (diameter 36.1 ± 20.3 mm, 6 bilateral) out of 177 patients underwent 18FDG-PET/CT and were included (17 M/19 F, age 61.2 ± 11.7 years). According to gold standards, 29 lesions were benign, 11 malignant [8 metastases (2 bilateral) and 1 adrenocortical carcinoma (ACC)] and 2 pheochromocytomas. The diagnosis of adrenal masses with a SUVratio > 1.5 was: 10 metastases, 1 ACC, 2 non-functioning adenomas, 1 hyperplasia and 1 pheochromocytoma. The SUVratio agreed with the diagnosis in 90.5% of patients; in the 4 discordant cases (SUVratio > 1.5 and non-malignant lesion) the diagnosis was: 2 non-functioning adenomas, 1 hyperplasia, 1 pheochromocytoma. The SUVratio cut-off of 1.5 showed 100% Sn, 87% Sp, 73% PPV, and 100% NPV. The SUVratio cut-off calculated in our population was 1.55 (Sn 100%, Sp 73.7%, AUC 0.868), with similar values excluding pheochromocytomas and metastases (SUVratio cut-off 1.49, Sn 100%, Sp 96.3%, AUC 0.988). Conclusion 18F-FDG PET/CT could help in decision making process avoiding unnecessary surgery. The SUVratio cut-off of 1.5 has a good performance in a heterogenous population.