Racial/Ethnic Disparities in Risk of Breast Cancer Mortality by Molecular Subtype and Stage at Diagnosis

Previous research has found significant survival disparities between African-American and white women among select stages and subtypes of breast cancer, however other racial/ethnic groups have been less well-studied. This study expands on previous research, examining differences in breast cancer-specific mortality across multiple racial and ethnic groups. Women diagnosed with a first primary invasive breast cancer between 2010 and 2016 who were 20 years of age or older at diagnosis were identified in the SEER database. Subtypes were defined by joint hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) status. Cox proportional hazards models for each stage and subtype were fit, with non-Hispanic white women as the reference group. Effect modification by age at diagnosis (<50, ≥50) was found. After multivariable adjustment, younger African American women had greater risks of breast cancer-specific death for all stages of HR+/HER2-, stages II-IV of HR+/HER2+, and stage I of HR-/HER2+ breast cancer. Asian/Pacific Islander women generally had a lower hazard of breast cancer-specific death. Older Hispanic white women had a lower hazard breast cancer-specific death for stages I-III HR+/HER2- and stage II HR-/HER2+ and TN breast cancer. These findings demonstrate that different racial/ethnic groups experience different risks of breast cancer-specific mortality by stage and subtype. Efforts to address survival disparities should place additional focus on young African American women, as they experience meaningful disparities in breast cancer-specific mortality.