Diagnostic importance of F-18-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

Does hepatic visualisation show residual/metastatic thyroid tissue in differentiated thyroid cancer?

Aim: Diffuse homogen hepatic uptake in whole-body scan (WBS) after radioiodine remnant ablation (RRA) suggests that there is occult or visible remnant thyroid tissue and/or tumor tissue. It is thought that the reason is hepatic metabolization of radioiodine (1311) marked thyroglobulin fragments which are secreted by remnant/tumor tissue. The aims of this study were to investigate whether the hepatic visualisation after radioiodine remnant ablation showed the presence of metastatic or residual disease in patients with differentiated thyroid cancer and also to investigate whether early or late WBS after RRA (RxWBS) had an effect on the physiological hepatic uptake. Material and Method: 201 DTC patients were evaluated (F/M: 152/49; mean age: 49.61 +/- 13 years (range: 18-85 years)) who referred for RRA. The therapeutic 1311 dose ranged from 100mCi to 200mCi. RxWBS was performed earlier (in 1-4th-day after RRA) in 106 patients (Group 1) and was performed later (in 5-9th-day after RRA) in 95 patients (Group 2). Results: Diffuse hepatic uptake were seen only in three patients (2.8%) and was not seen in 103 patients (97.2%) in Group 1. However, in Group 2 diffuse hepatic uptake was seen in 93 patients (97.9%) (p<0.05) and not seen only in 2 patients (2.1%). There is not a statistically significant relationship between the hepatic uptake and serum Tg. LT4 and TSH level. There is a statistically significant relationship between anti-Tg level and hepatic uptake. Discussion: Physiological diffuse hepatic uptake of radioiodine in WBS after RRA may not be seen during the early WBS. Thus, metastatic foci may be missed with early scanning. We conclude that RxWBS after RRA should be done in late period