Factors Affecting Brown Adipose Tissue Activation in Patients with Lymphoma Undergoing 18F-FDG- PET/CT

Background:18F-FDG PET/CT is an ideal diagnostic tool to investigate the metabolic activation of brown adipose tissue (BAT); high uptake in BAT interferes with scan interpretation. Aim: To evaluate the factors affecting BAT activation on 18F-FDG-PET/CT in patients with lymphoma. Methods: 18F-FDG-PET/CT scans of 208 consecutive patients with pathologically proven lymphoma were retrospectively reviewed PET/CT images were analyzed visually for the presence of FDG-avid BAT, its site, and its amount. For each area showing active BAT uptake, the maximum standardized uptake value (SUVmax) was calculated. In addition, the metabolic volume of activated BAT for each region was computed, and then the total metabolic volume (TMV) was recorded. Results: BAT was activated in 48/208 patients (23.1%), and most of them (45/48) had bilateral uptake in the supraclavicular regions. BAT activation was significantly more frequent among younger age groups (P ≤ 0.01), female gender (P = 0.01), and Hodgkin type (HL) (P < 0.01), but it was insignificantly more frequent in patients with higher body mass index (BMI) (P = 0.07). In univariate analysis, the patient’s age, sex, pathological type, injected dose, uptake period, fasting blood glucose, and outdoor temperature were significantly associated with BAT activation. Patient’s age (OR = 1.124, P < 0.01) and outdoor temperature (OR = 1.238, P < 0.01) continued to be significant independent predictor factors for BAT activation in multivariate regression analysis. Conclusion: BAT activation occurs more often in females, younger ages, and patients with HL. Lower outdoor temperature and younger age are the independent variables for prediction of BAT activation.