Obesity and survival of Asian American and White women with breast cancer

Abstract Background It is unknown whether lower obesity in Asian American women contributes to their better survival after breast cancer (BC) diagnosis compared with non-Latina White women. Methods In the Asian American Resiliency and Cancer (ARC) Cohort, with 3,919 Asian American and 4,978 non-Latina White women with BC, we examined associations between all-cause and BC-specific mortality, body mass index (BMI), and in a subset, waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR). Using multivariable-adjusted Cox proportional hazards regression, we estimated hazards ratios (HR) and 95% confidence intervals (CI), stratified by race/ethnicity, Asian ethnicity, menopausal status, and hormone receptor status. Results With 2,594 overall deaths and 1,120 BC deaths, all-cause mortality risk increased with higher BMI (per 5 kg/m2) in both Asian American (HR = 1.13, 95%CI=1.05-1.21) and non-Latina White (HR = 1.09, 95%CI=1.04-1.14) women. In the subset with abdominal adiposity measures (1,427 overall and 641 BC deaths), the range of HRs per unit increase was similar for Asian American (1.18 to 1.34) and White (1.14 to 1.19) women. For both overall and abdominal obesity, with a few exceptions, associations were observed primarily for postmenopausal women with hormone receptor-positive BC, although heterogeneity was not statistically significant. The survival difference between Asian American and non-Latina White women remained after adjustment for BMI (HR = 0.88, 95%CI=0.78-0.997). Obesity measures were not associated with BC-specific mortality, except for WHR and WHtR in Chinese women. Conclusions Our findings suggest that differences in overall and abdominal obesity do not explain the BC survival differences between the two populations.