Endocrine Abstracts (2009) 20 P189

Tumor/liver standardized uptake values ratio [lt]1.8 on FDG-PET has a high negative predicitive value to rule-out malignancy in patients with incidentally identified non-secreting adrenal tumours

David Taïeb, Laurent Tessonnier, Frederic Sebag, Isabelle Morange, Catherine De Micco, Bernard Conte-Devolx, Jean-François Henry & Olivier Mundler

CHU Timone, Marseille, France.

Purpose: The widespread use of high resolution cross-sectional imaging such as computer tomography (CT) and magnetic resonance imaging (MRI) for the investigation of the abdomen is associated with an increasing detection of incidental adrenal masses. 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) has proved to be an efficient tool in the diagnosis and follow-up of malignancies. We evaluated the ability of FDG-PET to distinguish benign from malignant adrenal masses when CT or MRI results had been inconclusive.

Methods: We included only patients with no evidence of hormonal hypersecretion and no personal history of cancer or in whom previously diagnosed cancer was in prolonged remission.

The visual interpretation, maximal standardized uptake values (SUVmax) and adrenal compared to liver uptake ratio were correlated with the final histological diagnosis or clinico-radiological follow-up when surgery had not been performed.

Results: Of 37 patients with 41 adrenal masses were prospectively evaluated. The final diagnosis was 12 malignant, 17 benign tumours, and 12 tumours classified as benign on the follow up. The visual interpretation and tumour/liver SUVmax ratios were more accurate than SUVmax alone, tumour diameter, or unenhanced density, with a sensitivity of 100% (12/12) and negative predictive value also of 100% (25/25). The use of 1.8 as the threshold for tumour/liver SUVmax ratio demonstrated 100% sensitivity and specificity.

Conclusion: FDG-PET/CT accurately characterises adrenal tumours with an excellent sensitivity and negative predictive values. A negative PET may predict a benign tumour that would potentially prevent the need for surgery of adrenal tumours with inconclusive conventional imaging. A cost-effectiveness study is required.