Predicting malignancy in patients with adrenal tumors using

BACKGROUND AND OBJECTIVES: (18)F-FDG-PET/CT parameters may help distinguish malignant from benign adrenal tumors, but few have been externally validated or determined based on definitive pathological confirmation. We determined and validated a threshold for (18)F-FDG-PET/CT maximum standard uptake value (SUVmax) in patients who underwent adrenalectomy for a nonfunctional tumor. METHODS: Database review identified patients with (18)F-FDG-PET/CT images available (training cohort), or only SUVmax values (validation cohort). Discriminative accuracy was assessed by area under the curve (AUC), and optimal cutoff value estimated by maximally selected Wilcoxon rank statistics. RESULTS: Of identified patients (n = 171), 86 had adrenal metastases, 20 adrenal cortical carcinoma, and 27 adrenal cortical adenoma. In the training cohort (n = 96), SUVmax was significantly higher in malignant vs. benign tumors (median 8.3 vs. 3.0, p < 0.001), with an AUC of 0.857. Tumor size did not differ. The optimal cutoff SUVmax was 4.6 (p < 0.01). In the validation cohort (n = 75), this cutoff had a sensitivity of 75%, and specificity 55%. CONCLUSIONS: (18)F-FDG-PET/CT SUVmax was associated with malignancy. Validation indicated that SUVmax ≥ 4.6 was suggestive of malignancy, while lower values did not reliably predict benign tumor.