Diagnostic importance of 18F-FDG PET/CT parameters and total lesion glycolysis in differentiating between benign and malignant adrenal lesions

PurposeBenign adrenal lesions are prevalent in oncologic imaging and make metastatic disease diagnoses difficult. This study evaluates the diagnostic importance of metabolic, volumetric, and metabolovolumetric parameters measured by fluorine-18-fluorodeoxyglucose (F-18-FDG) PET/CT in differentiating between benign and malignant adrenal lesions in cancer patients.Patients and methodsIn this retrospective study, we evaluated F-18-FDG PET/CT parameters of adrenal lesions of follow-up cancer patients referred to our clinic between January 2012 and November 2016. The diagnosis of adrenal malignant lesions was made on the basis of interval growth or reduction after chemotherapy. Patient demographics, analysis of metabolic parameters such as maximum standard uptake value (SUVmax), tumor SUVmax/liver SUVmean ratio (T/LR), morphologic parameters such as size, Hounsfield Units, and computed tomography (CT) volume, and metabolovolumetric parameters such as metabolic tumor volume and total lesion glycolysis (TLG) of adrenal lesions were calculated. PET/CT parameters were assessed using the Mann-Whitney U-test and receiving operating characteristic analysis.ResultsIn total, 186 adrenal lesions in 163 cancer patients (108 men/54 women; meanSD age: 64 +/- 10.9 years) were subjected to F-18-FDG PET/CT for tumor evaluation. SUVmax values (mean +/- SD) were 2.8 +/- 0.8 and 10.6 +/- 6; TLG were 10.8 +/- 9.2 and 124.4 +/- 347.9; and T/LR were 1 +/- 0.3 and 4.1 +/- 2.6 in benign and malignant adrenal lesions, respectively. On the basis of the area under the curve, adrenal lesion SUVmax and T/LR had similar highest diagnostic performance for predicting malignant lesions (area under the curve: 0.993 and 0.991, respectively, P<0.001). Multivariate logistic regression analysis showed that T/LR, adrenal lesion SUVmax, and Hounsfield Units were independent predictive factors for malignancy rather than TLG.ConclusionIrrespective of whether TLG was statistically highly significant for differentiating benign from malignant adrenal lesions, it did not reach the expected performance with a low negative predictive value. This may be because of the malignant but small and benign but large lesions on metabolovolumetric calculation.