Abstract 3625: Central and peripheral adiposity and breast cancer risk in postmenopausal women: A pooled analysis of 11 cohort studies

Abstract Background: Central and peripheral adiposity, measured by waist circumference (WC), hip circumference (HC), and waist-to-hip ratio (WHR), has been positively associated with postmenopausal breast cancer (BC) risk, but results are inconsistent after adjustment for body mass index (BMI). Using pooled individual-level data from 11 prospective cohorts, we evaluated associations between WC, HC, WHR, and a body shape index (ABSI; based on waist, height, and weight) and risk of postmenopausal BC overall and BC subtypes defined by receptor status. Methods: These preliminary analyses evaluated associations between WC, HC, WHR, and ABSI using consortium-wide quintiles and overall BC and tumor negative breast cancer (TNBC) in 402,682 postmenopausal women. Cox proportional hazards regression models were used to calculate hazard ratios (HRs) and 95% confidence intervals (95% CI), adjusting for age, year of questionnaire, study, family history of BC, and reproductive and lifestyle factors. Analyses were performed with and without adjustment for BMI. Results: During a median follow-up of 2.9-27.5 years across studies, 20,752 incident invasive BC were documented (N=998 TNBC). The pooled multivariable BMI-adjusted HRs (95% CIs) for postmenopausal BC comparing quintile 5 to 2 were 1.14 (1.08-1.21) for WC; 1.06 (0.99-1.14) for HC; 1.10 (1.05-1.15) for WHR, and 1.03 (0.98-1.08) for ABSI. Similar associations were observed among never-users of menopausal hormone therapy. The pooled multivariable BMI-adjusted HRs (95% CIs) for postmenopausal TNBC comparing quintile 5 to 2 were 1.13 (0.87-1.46) for WC; 0.74 (0.45-1.21) for HC; 1.45 (1.15-1.84) for WHR, and 1.18 (0.95-1.47) for ABSI. Conclusion: Higher compared to lower WC and WHR were associated with increased risk of postmenopausal BC, independent of BMI. Our findings suggest that individual and population-level strategies to prevent central adiposity could help reduce the risk of postmenopausal BC. Citation Format: Isaias Leon-Cepeda, Craigg Pickett, Stephanie A. Smith-Warner, Robert J. MacInnis, Jeanine M. Genkinger. Central and peripheral adiposity and breast cancer risk in postmenopausal women: A pooled analysis of 11 cohort studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3625.