Socioecologic Factors and Racial Differences in Breast Cancer Multigene Prognostic Scores in US Women.

Area of Science:

• Oncology
• Health Disparities
• Genomics

Background:

• Aggressive tumor biology in non-Hispanic Black women with early-stage, estrogen receptor (ER)-positive breast cancer contributes to mortality disparities.
• Socioeconomic factors may mediate racial differences in breast tumor biology, but this link is not well understood.

Purpose of the Study:

• To investigate if individual (insurance status) and contextual (area-level socioeconomic position, rural/urban residence) factors mediate racial differences in aggressive ER-positive breast tumors.
• To identify aggressive tumors using a high-risk gene expression profile (Oncotype DX recurrence score ≥26).

Main Methods:

• Retrospective cohort study of 69,139 women aged 18+ with stage I-II, ER-positive breast cancer diagnosed between 2007-2015.
• Analysis of Oncotype DX recurrence score (RS) as the primary outcome.
• Mediation analysis to assess the role of socioeconomic factors.

Main Results:

• Non-Hispanic Black and American Indian/Alaska Native women had a higher likelihood of high-risk RS compared to non-Hispanic White women.
• Non-Hispanic Black women in urban areas showed greater odds of high-risk RS.
• Lack of insurance, county-level disadvantage, and urban residence partially explained the higher odds of high-risk RS in non-Hispanic Black women (17% mediated).

Conclusions:

• Structural racism contributes to breast cancer outcome disparities by influencing aggressive tumor biology.
• Further research with comprehensive social and environmental measures is needed to understand social determinants of aggressive ER-positive tumor biology in minoritized women.