Survival Disparities in Patients With Metastatic Breast Cancer

De novo metastatic breast cancer (dnMBC) is typically a fatal diagnosis. Although better treatments have improved survival, it is unclear whether these improvements confer similar benefits for all patients. We sought to evaluate the association of race/ethnicity and insurance status with survival outcomes in patients with dnMBC.

Patients diagnosed with dnMBC between 1988 and 2016 were selected from SEER. Differences were examined by race/ethnicity (non-Hispanic White [NHW], non-Hispanic Black [NHB], non-Hispanic other [NHO], or Hispanic) and insurance status (private/Medicare, Medicaid, or uninsured). Overall survival (OS) and cancer-specific survival were estimated, and multivariable models were used to identify factors associated with survival, after adjustment.

47,034 patients were included (median follow-up, 91 months). Most patients were NHW (67.2%) and insured (73.9%). Overall, NHB patients had the worst outcomes (median OS, 21 months), while NHO patients had the best (34 months). Similarly, uninsured patients had the worst survival outcomes (22 months), while insured (private/Medicare) patients had the best (31 months). Over time, survival generally improved across all groups, although disparities persisted. After adjustment, only NHB patients had significantly worse outcomes compared with NHW patients (OS: hazard ratio [HR], 1.24 [95% CI, 1.17 to 1.31]; P < .001), as did uninsured compared with insured patients (OS: HR, 1.29 [95% CI, 1.16 to 1.44]; P < .001).

Racial/ethnic and insurance disparities in breast cancer survival persist, even in a dnMBC-only cohort, with notably worse outcomes for NHB and uninsured patients. Given that race and ethnicity are often considered social constructs in the United States specifically, improving health care access has the potential to improve survival in this patient population. Systemic factors other than insurance status leading to disparities must be identified and addressed to provide equitable treatment in this vulnerable patient population.