Incidental Non-secreting Adrenal Masses in Cancer Patients: Intra-individual Comparison of 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography with Computed Tomography and Shift Magnetic Resonance Imaging

The ability of integrated F-18-fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) to distinguish between benign and malignant incidental non-secreting adrenal masses was evaluated in cancer patients. Results were compared with those of CT and shift magnetic resonance imaging (MRI). A total of 1832 cancer patients who had undergone FDG PET/CT scans were retrospectively evaluated. Visual interpretation, tumour maximum standardized uptake value (SUVmax), liver SUVmax and tumour/liver SUVmax ratios were correlated with the findings of CT, shift MRI and final diagnosis (based on biopsy or clinical/radiological follow-up). A total of 109 adrenal masses were found: 49 were malignant and 60 were benign on final diagnosis. A tumour/liver SUVmax ratio threshold of 1.0 was more accurate in differentiating the tumour type than tumour SUVmax or visual interpretation alone. Diagnostic accuracy of CT and shift MRI (92 - 97%) was similar to that for FDG PET/CT (94 - 97%). In conclusion, FDG PET/CT accurately characterizes adrenal tumours, with excellent sensitivity and specificity. Use of 1.0 as the threshold for the tumour/liver SUVmax ratio seems to be promising for distinguishing benign from malignant adrenal masses in cancer patients.