Abstract
BACKGROUND: Brown adipose tissue (BAT) regulates metabolic homeostasis, yet its role in tumor presence remains undefined. This study investigates the associations among BAT, body mass index (BMI), and tumor presence in a large Chinese cohort. METHODS: We retrospectively analyzed 1,736 adults who underwent (18)F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography ((18)F-FDG PET/CT) at Shanghai East Hospital (2016-2024). Patients were grouped by BAT status with propensity score matching and sex stratification. BAT was identified by FDG uptake at typical depots with CT density criteria. Statistical analyses included chi-square tests, regression models, and mediation analysis (structural equation modeling with bootstrapping) to assess the role of BMI in the BAT-tumor presence association. RESULTS: The presence of BAT was associated with younger age, female sex, and lower BMI. In multivariable logistic regression, age (p < 0.001) and BMI (p = 0.014) were independently associated with tumor presence. After propensity score matching (PSM), sex-stratified mediation analysis showed that in females, BAT was indirectly associated with a lower likelihood of tumor presence (Natural Indirect Effect OR = 0.88, 95% CI 0.72-0.98), whereas no significant mediation effect was observed in males. Among cancer patients, individuals with BAT had a significantly lower BMI compared to individuals without BAT (overall: 21.08 vs. 23.34; females: 21.33 vs. 22.97; males: 19.65 vs. 24.68). CONCLUSIONS: Our findings indicate that BAT and tumor presence are statistically associated in a sex-specific manner, with BMI potentially playing a mediating role in females. The consistently lower BMI among BAT(+) cancer patients further indicates a plausible link between BAT and body weight regulation. These observations warrant further investigation to elucidate the underlying mechanisms.