Abstract PS2-08-08: Comparison of anthropometric, systemic and mammary adiposity measures in patients with breast cancer

Abstract Introduction: The obesity-breast cancer (BC) connection is increasingly recognized for its clinical relevance, especially as the proportion of women with BC and overweight/obesity continues to rise. While use of body mass index (BMI) as an adiposity measure is convenient, it is unclear how it relates to other anthropometric, systemic and local adiposity measures as well as with various endocrine, metabolic and inflammatory measures in patients with BC. To explore these complex associations, we launched the prospective FATLAS study (NCT04200768). Methods: FATLAS is a monocentric study set-up at University Hospitals Leuven enrolling cancer treatment naïve patients with BC scheduled for upfront surgery for whom tissue and blood samples are collected. Global adiposity is assessed via body fat percentage, visceral fat (TANITA RD-545), waist-to-hip ratio (WHR) and BMI. Local adiposity is evaluated by the median size of cancer-associated adipocytes (CAA) and distant mammary adipocytes (DA) in the adjacent normal breast tissue (HALO v3.6.4134). Inflammation markers include global (CRP, β-globulin fraction and WBC, eosinophil and lymphocyte count) and local markers (Crown-like Structures (CLS) density, stromal tumor infiltrating lymphocytes (sTIL), IL6, IL18 mRNA expression). Metabolic dysregulation is assessed using global (HbA1c, leptin, HDL, LDL, IGF1 levels, fasting C-peptide and insulin, metabolic syndrome score) and local markers (IGF1, IGF1R and leptin mRNA expression). Correlations were assessed using Spearman coefficients. Results: We included 96 women with ER+/HER2- BC (62% with no special type BC (NST) and 38% with lobular breast cancer (ILC)) of which 41% with normal-weight, 39% with overweight and 20% with obesity. 33% were diagnosed at stage I, 61% at stage II and 5% at stage III. 60% of patients were postmenopausal. Mean age at diagnosis was 57 years. Both body fat percentage and visceral fat showed a strong correlation with BMI (ρ = 0.82, ρ = 0.82), but not with WHR (ρ = 0.32 and ρ = 0.27). Results were consistent across pre/peri- and postmenopausal patients. Adipocyte size increased with BMI in both DA and CAA (ρ = 0.37, ρ = 0.52) with a more pronounced trend in CAA (Kruskal-Wallis 0.001 and p = 0.002 respectively). CAA were consistently smaller than DA across all BMI categories (p0.05) . The association between adiposity and inflammation was limited when considering all patients, but we did observe significant correlations between global adiposity and CRP (e.g. BMI ρ = 0.53). In pre/perimenopausal patients, global adiposity (BMI) correlated stronger with several systemic (e.g. neutrophil count ρ = 0.56) and local inflammation markers (IL6: ρ = 0.30 and IL18: ρ = 0.40). Regarding local adiposity, DA correlated stronger with several systemic inflammation markers (e.g. CRP ρ = 0.43, CAA ρ = 0.34), while CAA correlated stronger with local inflammation markers (e.g. IL6 CAA: ρ = 0.51; DA: ρ = 0.25). In postmenopausal patients, all global adiposity markers - except WHR - correlated only with CRP (e.g. BMI: ρ = 0.53), while significant correlations were observed between local marker CAA and local inflammation (CLS: ρ = 0.48; sTIL: ρ = -0.30) and systemic CRP (ρ = 0.38). Regarding metabolic dysregulation, BMI correlated with several systemic (e.g. circulating leptin ρ = 0.80) and local markers (e.g. mammary leptin levels ρ = 0.52), with this observation being more pronounced in premenopausal patients (ρ = 0.84 and ρ = 0.69). Conclusion: BMI correlates with body and visceral fat but less with mammary adipocyte size. It remains associated with inflammation and metabolic dysregulation, particularly in pre/perimenopausal patients. Citation Format: J. Van Cauwenberge, I. Bachir, F. Richard, M. Maetens, T. Geukens, K. Van Baelen, M. De Schepper, G. Zels, H. Nguyen, D. Lambrechts, E. Vanderheyden, T. Van Brussel, I. Nevelsteen, A. Smeets, H. Wildiers, P. Neven, G. Floris, C. Desmedt. Comparison of anthropometric, systemic and mammary adiposity measures in patients with breast cancer abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-08-08.