18F-FDG PET for the identification of adrenocortical carcinomas among indeterminate adrenal tumors at computed tomography scanning.

BACKGROUND: 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) has been proposed for the evaluation of adrenal tumors. However, only scarce data are available to evaluate its usefulness for the identification of primary adrenal carcinomas in patients with no previous history of cancer and equivocal tumors on computed tomography (CT) scan. The objective of the present study was to evaluate the diagnostic performance of 18F-FDG-PET to predict malignancy in such patients.

METHODS AND PATIENTS: This was a retrospective study carried out from 2006 to 2009 in a single university hospital center. Twenty-three consecutive patients without previous history of cancer investigated for adrenal tumors without features of benign adrenocortical adenoma on CT scan but no obvious ACC underwent 18F-FDG PET. All patients underwent adrenalectomy because of CT scan characteristics regardless of the results of 18F-FDG PET. The ratio of maxSUV adrenal tumor on maxSUV liver (adrenal/liver maxSUV ratio) during 18F-FDG PET was compared to Weiss pathological criteria.

RESULTS: Seventeen patients had an adrenal adenoma, 2 had small size adrenal carcinomas (<5 cm), 1 had an angiosarcoma, and 3 had noncortical benign lesions. An adrenal/liver maxSUV ratio above 1.6 provided 100% sensitivity, 90% specificity, and 100% negative predictive value for the diagnosis of malignant tumor.

CONCLUSIONS: Because of its excellent negative predictive value, 18F-FDG-PET may be of help in avoiding unnecessary surgery in patients with non-secreting equivocal tumors at CT scanning and low 18F-FGD uptake.