Racial disparity in microvascular function among women with newly diagnosed breast cancer.

Cardiovascular disease (CVD) is a leading cause of death in women with breast cancer, with non-Hispanic Black (NHB) women experiencing higher CVD-related mortality compared with non-Hispanic White (NHW) women. Differences in vascular health may contribute to this disparity. This study assessed cardiovascular health in NHB and NHW women with breast cancer. Forty-five women (25 NHW, 20 NHB) within 2 yr of diagnosis [American Joint Committee on Cancer (AJCC) stages 0-3] participated. Clinical laboratories, senescence-associated secretory phenotype (SASP), and allostatic load were assessed. Flow-mediated dilation (FMD) assessed conduit vessel function; cutaneous postocclusive reactive hyperemia (PORH), local thermal heating (LTH), and iontophoresis of acetylcholine (Ach) assessed microvascular function. Pulse-wave velocity (PWV) and pulse-wave analysis (PWA) measured arterial and aortic stiffness, respectively. Maximal exercise testing (V̇o_2peak) and near-infrared spectroscopy (NIRS) assessed skeletal muscle oxidative capacity (SMOC). Participants were enrolled 6 ± 5 mo after diagnosis. Chemotherapy exposure (P = 0.897) and cancer stage (P = 0.382) were not different between the groups. NHW women were older (59 ± 12 vs. 53 ± 12 yr; P = 0.090), but body mass index (BMI), clinical laboratories, SASP, and allostatic load did not differ (all P > 0.05). NHW women demonstrated higher PORH (P < 0.001), LTH (P < 0.001), and Ach responses (P = 0.033), which remained significant after adjusting for cancer stage and chemotherapy. No differences were seen in FMD, PWV, PWA, V̇o_2peak, or SMOC. NHB women with breast cancer exhibited impaired microvascular function compared with NHW women, independent of social determinants, cancer stage, or chemotherapy. These findings suggest microvascular dysfunction may contribute to racial disparities in CVD risk after breast cancer diagnosis.NEW & NOTEWORTHY This study is the first to show that non-Hispanic Black women with breast cancer have impaired microvascular function compared with non-Hispanic White women with breast cancer, despite similar social determinants of health, cancer stage, and chemotherapy exposure. These findings suggest early microvascular dysfunction may contribute to racial disparities in cardiovascular risk after breast cancer and highlight the need for targeted cardiovascular interventions in this high-risk group.