Social determinants of health and breast cancer disparities in the United States: a multilevel review of barriers to diagnosis and treatment

Background US breast cancer mortality has more than halved since 1975, but the decline has not been shared equally. Black women’s death rates remain 36% higher than White women’s, and rates among American Indian and Alaska Native women have not fallen in three decades. Within-subtype survival gaps are widest in hormone receptor-positive, HER2-negative disease, where sustained treatment matters most, a pattern more consistent with unequal access than with biology alone. Approach We conducted a narrative review with a structured, documented search of US evidence (PubMed, 2010 to 2026, prespecified eligibility criteria) on five domains of social determinants of health: insurance status and healthcare access, neighborhood socioeconomic deprivation, structural racism, geographic access, and individual socioeconomic status. We present them as four interrelated levels (upstream structural determinants, neighborhood and geographic exposures, health-system and access mediators, and individual socioeconomic consequences) and examine two outcomes, stage at diagnosis and guideline-concordant treatment, labeling estimates by design and outcome definition. Findings In registry and national database analyses, uninsured women had 2.6-fold higher odds of stage IIIB to IV disease than privately insured women, and late-stage diagnosis fell after Medicaid expansion in quasi-experimental comparisons. Neighborhood deprivation was associated with later stage and, in mediation analyses, statistically accounted for about 45% of the Black-White difference in all-cause mortality; historical redlining was associated with higher mortality, roughly half mediated by present-day neighborhood conditions. Rural residence carried a small excess of later stage and a larger deficit in radiation receipt linked to travel distance. Compared with private insurance, Medicaid or no insurance was associated with less breast conservation and reconstruction, more omission of radiation, lower receipt of guideline-concordant chemotherapy, earlier discontinuation of endocrine therapy, and lower uptake of immunotherapy. Most evidence is observational, and area-level measures assigned to individuals risk contextual misclassification. Implications Patient navigation improves screening uptake and diagnostic timeliness in trials but has no demonstrated survival benefit; Medicaid expansion is associated with earlier stage, timelier treatment and lower mortality in difference-in-differences analyses. Simulation modeling suggests equalizing treatment access would narrow, not close, the mortality gap. Closing it requires attention to coverage design, neighborhood investment, and oncology workforce distribution.