Tumor biology and access to care and metastatic breast cancer outcomes

PURPOSE: To understand how access to care influences metastatic breast cancer burden (MBC) while accounting for molecular tumor characteristics, and identify interventions to reduce metastatic disease burden. METHODS: The Carolina Breast Cancer Study is a population-based cohort with invasive breast cancer (diagnosed 2008-2013). Both de novo metastasis (stage IV at diagnosis) and distant recurrence were evaluated (12 years of follow-up. Tumor data were from medical records, pathology reports, and RNA expression data. Social variables and access to care were from participant surveys. Generalized linear models were used to estimate associations of biological and access characteristics with MBC; Cox models were used to estimate recurrence hazards. RESULTS: 464/2998 patients (15.5%) had MBC (n = 109 de novo; n = 355 recurrent). MBC was associated with grade 3 vs 1 (odds ratio (OR) = 4.15, 95% CI: 2.60, 6.99), LumB vs LumA (OR = 2.08, 95% CI: 1.48, 2.90), and high vs low PAM50 risk of recurrence score (OR = 4.45, 95% CI: 2.93, 6.99) vs. non-MBC. MBC was associated with Black race (Hazard ratio (HR) = 1.66, 95% CI: 1.32, 2.11), poverty (HR = 1.47; 95% CI: 1.09, 1.99), and low education (HR = 1.48, 95% CI: 1.03, 2.13). Controlling for healthcare access (screening, regular care, delayed treatment, and community healthcare) attenuated associations with metastasis for poverty and education, but had lesser effects on race associations. CONCLUSIONS: Disparities in MBC burden persist after adjustment for individual- and community-level healthcare access. Reducing burden of MBC in Black women necessitates simultaneous targeting of biological and access to care factors.