Brown Adipose Tissue at F-18 FDG PET/CT: Correlation of Metabolic Parameter with Demographics and Cancer-Related Characteristics in Cancer Patients

Background: The effect of various environmental and intrinsic stimulators on the development of brown adipose tissue (BAT) has been widely investigated by PET-based researches. However, evidence regarding the influencing factors on the level of BAT metabolic activity is scarce. Objectives: The aim of the present study was to evaluate the frequency of cancer-related characteristics in addition to anthropometrics and demographics in BAT-bearing cancer patients at 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) scan and any correlation between the level of BAT metabolic activity and the influencing factors. Patients and Methods: Reports from a total of 3762 F-18 FDG PET/CT scans were retrospectively reviewed to identify BAT-bearing cancer population. Demographic, anthropometric and cancer related characteristics were recorded. Maximum standardized uptake values (SUVmax) was measured separately for each anatomical region. Descriptive quantitative variables were expressed as either frequency or mean. Independent T test, Mann-Withney U test, Pearson correlation coefficients, one-way analysis of variance and linear regression test (IBM SPSS version 23) were used as appropriate (P value <0.05) Results: Sixty-two F-18 FDG PET/CT studies demonstrated BAT related 18-F FDG uptake (1.6%, 32% male, 68% female, P = 0.007, mean age 22.9). Lymphoma (43.5%) and treatment response evaluation (54.54%) were the most frequent type of cancer and reason for referral, respectively. Most patients were in status partial or complete metabolic response to treatment. Fifty-four point eight percent of patients had at least one metabolically active cancer-related lesion. BAT detection rate was higher in females in all adult age groups, younger age (< 40 years old), body mass index (BMI) and body fat (BF) below the obesity cut off and autumn/winter seasons. The dominant distribution pattern of BAT depots was neck, mediastinum, paravertebral (33.87%) with the highest level of metabolic activity in the axillary region. SUVmax demonstrated a weak inverse correlation with age (0.015), evidence of active malignant disease and no recent treatment. Linear regression test demonstrated that age (P = 0.021) and recent treatment (P = 0.033) have independent correlation with BAT SUVmax. Conclusion: The present study provided evidence for age and chemotherapeutic agents on the level of BAT metabolism. In addition, there is a suggestion for different pathways involved in BAT development and regulation of the level of metabolic activity.