Prospective study of cardiometabolic health and risk of breast cancer subtypes among US Black women

In the United State, cardiometabolic conditions and aggressive breast cancers are both more common among Black women than White women. A prospective study, using data from 57,453 participants in the Black Women’s Health Study (BWHS), evaluated associations of body mass index (BMI), type 2 diabetes , hypertension, and hypercholesterolemia with the incidence of breast cancer. Pathology records were used to classiy cases by ER status and subtype (luminal A-like, luminal B-like, HER2-overexpressed, and triple-negative). Associations were adjusted for age, reproductive factors, and lifestyle factors. Among postmenopausal women, BMI ≥ 30 kg/m² versus < 25 kg/m² was associated with increased risk of ER+ (HR 1.35; 95% CI 1.15-1.59) breast cancer and luminal A-like subtype (1.54; 1.19-1.98). No others cardiometabolic factors were associated with breast cancer subtypes. Relative to those with no cardiometabolic factors, postmenopausal women with ≥ 3 cardiometabolic conditions had a 43% higher risk of ER+ cancer (95% CI 1.04-1.97) and a 38% lower risk of ER- cancer (0.37-1.02; p for heterogeneity 0.0006). Analysis of all possible combinations of 2 or 3 factors resulted in HRs> 1.0 for ER+ breast cancer and HR not significantly different from 1.0 for ER- breast cancer. There were no statistically significant findings among premenopausal women. The authors conclude that in this large cohort of Black women, poorer cardiometabolic health was associated with higher ER+ and lower ER- breast cancer risk among postmetabolic women (graphical abstract).