Role of 18F-FDG PET/CT in the differential diagnosis of primary benign and malignant unilateral adrenal tumors

Abstract

Background: This retrospective study was performed to estimate the clinical role of whole-body positron emission tomography/computed tomography (PET/CT) using 2-[18F] fluoro-2-deoxy-D-glucose (FDG) in the differential diagnosis of primary benign and malignant unilateral adrenal tumors. Methods: A total of 64 patients (31 male, 33 female; age range: 3-76 years, mean: 48.5) with a confirmed unilateral adrenal tumor underwent 18F-FDG PET/CT examination for diagnosis and staging. The whole-body 18F-FDG PET/CT examination excluded metastasis, and all patients were confirmed by operation and biopsy pathology. Their clinical data and pathological results were collected. On visual analysis of PET/CT imaging, adrenal uptake was based on a three-scale grading system. The region of interest (ROI) was delineated in the liver and the renal lesion site. Standardized uptake value (SUV) measurements were determined on a standardized reconstruction, and the maximum values (SUVmax) of the lesion and liver were measured. The ratio of tumor to the liver was defined as T/L. Visual interpretation, SUVmax-receiver operating characteristics (ROC) method, and T/L-ROC method were used to analyze the diagnostic accuracy. Results: A total of 64 lesions (48 benign, 16 malignant lesions) were detected. The visual analysis found that 100% of Grade I cases were benign, 90.9% of Grade II cases were benign, and 65.1% of Grade III cases were benign. The SUVmax of malignant lesions (10.0±5.8) was higher than that of benign lesions (5.4±5.3, P<0.05). The T/L was 3.39±1.79 for malignant lesions and 1.99±2.09 for benign lesions (P<0.05). In the differentiation of primary benign and malignant unilateral adrenal tumors, the sensitivity, specificity, and accuracy of the SUVmax-ROC method (cut-off value =5.65) were 81.25%, 72.91%, 75.00%, and the positive and negative predictive values were 50.00% and 92.11%, respectively. The sensitivity, specificity, and accuracy of the T/L-ROC method (cut-off value =1.52) were 93.73%, 62.50%, 70.31%, and the positive and negative predictive values were 46.88% and 96.77%, respectively. Conclusions: 18F-FDG PET/CT improved diagnostic accuracy in differentiating primary benign and malignant unilateral adrenal tumors. There was a high negative predictive value, and for positive prediction, other tracer imaging is needed for differential diagnosis.