The value of adding ¹⁸F-FDG PET/CT to adrenal protocol CT for characterizing adrenal metastasis (≥ 10 mm) in oncologic patients

OBJECTIVE. The objective of our study was to evaluate the value that PET/CT adds to adrenal protocol CT for characterizing adrenal metastasis in oncologic patients. MATERIALS AND METHODS. Sixty-eight oncologic patients with 68 adrenal masses underwent both adrenal protocol CT and ¹⁸F-FDG PET/CT. For adrenal protocol CT, metastasis was diagnosed if a mass measured more than 10 HU on unenhanced CT and if the absolute and relative percentage washouts were less than 60% and 40%, respectively. For PET/CT, metastasis was diagnosed if FDG uptake of the lesion was equal to or greater than that of the liver. Diagnostic accuracies were compared between these two imaging modalities. RESULTS. The accuracy of adrenal protocol CT and PET/CT for a metastatic lesion, defined as a lesion with FDG uptake equal to or higher than that of the liver, was 85.3% (58/68) and 76.5% (52/68), respectively. However, the accuracy of PET/CT increased to 89.7% (61/68) when a lesion with high FDG uptake alone was considered a metastatic lesion. When both adrenal protocol CT and PET/CT were positive for metastasis, the accuracy increased to 91.2% (62/68), but the sensitivity decreased to 70.6% (12/17). CONCLUSION. Adding PET/CT to adrenal protocol CT improves the accuracy for adrenal metastasis in oncologic patients when a lesion with high FDG uptake alone is considered metastasis.