Characterization of adrenal metastatic cancer using FDG PET/CT.

The adrenal gland is a common location for metastasis from a primary tumor in another organ. This study evaluated the properties of adrenal lesions in cancer and non-cancer patients and investigated what variables may help predict adrenal metastasis. This retrospective study used 18fluorodeoxyglucose PET/CT on 371 patients with adrenal lesions (N = 260 with a primary tumor and N= 111 with an unknown primary tumor). Parameters such as the presence of a tumor, nodule, enlarged adrenal, maximum standardized uptake (SUVmax ratio) were evaluated. Univariate and multivariate analysis were used to identify variables that may predict risk of adrenal metastasis. Subjects with adrenal metastasis versus those without had a higher frequency of primary lung tumors (53.7% versus 28.6%, respectively; P≤ 0.001) but a lower frequency of gastrointestinal cancer (9.3% versus 20.4%, respectively; P = 0.014). The frequency of other abnormalities including nodules and enlarged adrenals were similar between cancer and non-cancer subjects. A higher proportion of subjects with adrenal metastasis regardless whether the primary tumor site in the lung, gastrointestinal track, or liver had SUVmax ratio > 2.5 versus those with no adrenal metastasis. In this cohort of subjects, the greatest proportion of subjects with adrenal metastasis was those with primary lung cancer. Univariate and multivariate analysis indicated that age, SUVmax ratio, and the presence of metastasis in multiple organs were independent variables for having adrenal metastasis. In this study, FDG PET/CT was useful in characterizing adrenal lesions including determining whether they were benign or malignant. This technology allowed us to identify characteristics that may useful in predicting adrenal metastasis and cancer severity.