Abstract 3407: Physical activity and post-menopausal breast cancer in the Multiethnic Cohort Study

Abstract Much research has been conducted on the relationship between physical activity and breast cancer, with meta-analyses showing 10 – 21% reduction in breast cancer risk for postmenopausal women with high compared to low level of physical activity. However, few studies have explored this relationship in non-Caucasian women. We analyzed data from 74,177 post-menopausal African American, Caucasian, Japanese American, Latina, and Native Hawaiian women in the Multiethnic Cohort in Hawaii and California. Data on physical activity (hours and metabolic equivalents (METs)) was based on a self-administered questionnaire at baseline (1993–1996). Multivariate Cox proportional hazards models provided estimates of hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for risk factors. We observed no associations between breast cancer risk and hours of moderate/vigorous activity per week (HR=1.01, 95% CI: 0.91-1.10, Ptrend=0.71), MET-hours of moderate/vigorous activity per week (HR=1.03, 95% CI: 0.94-1.13, Ptrend=0.92), and total METs-measured as average MET level per day multiplied by 7 (HR=0.94, 95% CI: 0.86-1.03, Ptrend=0.37) when comparing the highest quartile to the lowest. When examining the data across race/ethnicity, we observed a reduction in risk of breast cancer for total METs (HR=0.75, 95% CI: 0.61-0.94, Ptrend=0.05) among Latina women. Analysis across strata of BMI showed no differences across subgroups. In this study, we did not observe any consistent protective association between physical activity and breast cancer risk. Citation Format: Jasmeet K. Gill, Gertraud Maskarinec, Song-Yi Park, Lynne Wilkens, Loic Le Marchand. Physical activity and post-menopausal breast cancer in the Multiethnic Cohort Study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3407.