145 Racial Differences in Outcomes and Health Care Utilization Among Patients With HR-Positive, HER2-Negative Metastatic Breast Cancer Treated With CDK4/6 Inhibitors: A Real-World Analysis

Background

CDK4/6 inhibitors combined with endocrine therapy represent the standard of care for hormone receptor (HR)–positive, HER2-negative metastatic breast cancer (mBC). Despite their widespread use, real-world data evaluating racial differences in treatment outcomes and health care utilization remain limited. This study examined survival, progression, and hospital utilization among Black and White patients receiving CDK4/6 inhibitors.

Materials and Methods

We performed a retrospective cohort study using the TriNetX Global Collaborative Network, including adults (≥18 years) with HR-positive/HER2-negative mBC who initiated palbociclib, ribociclib, or abemaciclib in combination with endocrine therapy. Black and White patients were propensity score matched (1:1) based on age, sex, hypertension, diabetes, chronic kidney disease, and smoking status. Outcomes included all-cause mortality, progression-free survival (PFS), and health care utilization, defined as emergency department visits or inpatient admissions. Outcomes were assessed at 6 months, 1 year, and during long-term follow-up using Kaplan-Meier estimates and Cox proportional hazards models.

Results

After matching, 2093 Black patients were compared with 2093 White patients. All-cause mortality was similar between groups across all time points (1-year HR, 1.05; 95% CI, 0.88-1.25; P = .62). PFS was also comparable (1-year HR, 0.97; 95% CI, 0.78-1.20; P = .76). In contrast, Black patients experienced significantly higher health care utilization. At 1 year, the risk of emergency department visits or inpatient admissions was 47.7% among Black patients vs 43.4% among White patients (HR, 1.17; 95% CI, 1.07-1.28; P = .001), with similar findings observed during long-term follow-up.

Conclusions

In this large real-world cohort of patients with HR-positive/HER2-negative mBC treated with CDK4/6 inhibitors, Black and White patients experienced comparable survival and progression outcomes. However, Black patients had significantly higher rates of hospital utilization despite similar oncologic outcomes. These findings suggest that disparities in supportive care, access to outpatient management, or broader structural factors—rather than differences in treatment efficacy—may contribute to observed utilization differences and warrant targeted interventions to improve equity in cancer care delivery.