Abstract B106: Racial/ethnic disparities in risk of breast cancer mortality by molecular subtype and stage at diagnosis
Authors: Lorona Nicole C , Malone Kathleen E , Li Christopher I 
Published: September 2020

Background: 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. Methods: Women diagnosed with a first primary invasive breast cancer between 2010 and 2016 who were between 20 and 85 years of age 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 (&lt;50, ≥50) was found, so models additionally including an interaction term for binary age at diagnosis, with a linear age term for the main effect, were fit. Four different models were fit to adjust for different sets of confounders, adding in additional covariates with each model. Results: 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+, stage III TN breast cancer, and stage I and IV 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 of breast cancer-specific death for stages I-III HR+/HER2- and stage II TN breast cancer. Generally, insurance status explained in part the observed disparities; however, many of the observed disparities were still statistically significant after adjustment for tumor grade, treatment characteristics, and insurance status. Conclusions: These findings demonstrate that different racial/ethnic groups experience different risks of breast cancer-specific mortality by stage and subtype. By considering different models adjusting for different factors we were able to observe the extent to which these factors account for initially observed disparities. Insurance status, as a proxy for other health care and socioeconomic factors, may drive some of the observed differences in mortality; however, other factors, such as hormonal treatment or obesity, may be responsible for the remaining disparities. Efforts to address survival disparities should place additional focus on young African American women, as they experience meaningful disparities in breast cancer-specific mortality, particularly for HR+ subtypes.

Citation Format: Nicole C Lorona, Kathleen E Malone, Christopher I Li. Racial/ethnic disparities in risk of breast cancer mortality by molecular subtype and stage at diagnosis [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B106.