(SLB-061) Racial Disparity in Cardiovascular Outcomes among Older Women with Breast Cancer receiving Anthracycline

Background: Anthracyclines (ACs) are known for significant cardiotoxic effects, increasing the risk of serious cardiovascular (CV) events. In fact, older breast cancer (BC) patients are more likely to die from CV disease rather than cancer. However, our understanding of racial disparities in AC-induced cardiotoxicity outcomes is limited.

Objectives: We quantified racial disparities in major adverse cardiac events (MACE) incidence and examined the role of social vulnerability index (SVI) and clinical factors (CFs) in mediating these disparities among patients with BC receiving AC.

Methods: This retrospective cohort study used the SEER-Medicare database, including females aged ≥ 66 years with a new primary diagnosis of BC (2007-2020), who received AC within one year after diagnosis. The primary outcome was a 5-year incidence of MACE defined as a composite of heart failure, myocardial infarction, myocarditis, cardiomyopathy, ischemic heart disease, transient ischemic attack/stroke, revascularizations, cardiovascular mortality). Patients with non-CVD mortality, or loss to follow-up were censored, with adjustment made using inverse probability of censoring weighting. Associations between race and MACE incidence after AC initiation were evaluated using weighted proportional hazards models. Mediation analysis determined the contributions of potential mediators, including county-level theme-specific SVI, cancer-related characteristics (grade, stage, surgery, radiotherapy, chemotherapy), and CFs (comorbidities, co-medications).

Results: Among 5,574 patients (230,541 person-months), 2,128 MACE events occurred (restricted mean survival time: 44.5 months). Black patients were associated with higher hazard of MACE with a hazard ratio (HR) of 1.28 (95% CI: 1.09 – 1.52) and 5-year relative risk difference (RD) of 0.08 (95% CI 0.03 – 0.13) compared to White patients. Without right-censoring adjustment, HR was 1.18 (1.03 – 1.34) and RD was 0.05 (0.01– 0.09). While excluding SVI, HR was 1.3 (1.09 – 1.50) and RD was 0.08 (0.03 – 0.12). Mediation analysis showed that total proportion mediated was 61.2% (37.2–101.9%), primarily by CFs, which mediated 43.6% (26.1–70.1%). Chronic nutritional-deficiency anemia [10.5% (5.7–17.9%)] and obesity [5.9% (1.8–13.2%)] contributed most to the observed mediation. Socioeconomic status mediated 4.6% (-2.6 – 11.9%) of the disparities.

Conclusions: MACE incidence was significantly higher in Black patients after initiating AC compared with their White counterparts. Clinical factors, especially nutritional-deficiency anemia and obesity, substantially mediated the disparity in MACE risk. Early dietary interventions and targeted preventive strategies could help mitigate inequities in MACE among older women with BC.