Abstract Although the incidence of estrogen receptor positive (ER+) breast cancer is similar for Black and White women in the US, Black patients have significantly worse outcomes. Black women in the US have also have worse health care options, poorer educational opportunities, and face significantly higher rates of poverty burden. Collectively contributing to an overall lower socioeconomic status (SES) compared to White women. However, cancer health disparities research primarily exists in two forms: 1) The impact of socioeconomic factors on cancer outcomes, and 2) The molecular underpinnings associated with genetic ancestry on cancer biology. This siloing results in an incomplete picture of how systemic factors (i.e. racism, poverty burden) contribute to the biology of breast cancer in addition to, and along-with, ancestral genetics. Consequently, differences in the molecular biology between tumors from Black and White women remains a gap in knowledge in the field, because ancestral genetics cannot explain the breadth of disparities that patients face. Recent studies have found that Black cancer patients have a unique gene expression profile that may modulate treatment response. For instance, ER+ breast tumors in Black women have distinct signatures of defective DNA damage repair (DDR) that associate with more aggressive tumor growth. However, how factors of SES contribute to these differences in molecular biology and whether these differences alter treatment response remain unknown. One challenge to addressing these questions is that existing datasets significantly underrepresent Black women and are not sufficiently annotated to understand the complex interplay between molecular biology and factors of SES. Here, we present analysis of RNA expression datasets from 60 ER+ patient tumors (38 Black, 22 White), with corresponding SES and patient outcome annotations. Altogether, these data begin to define the complex interplay between factors of SES and changes in gene expression in addition to patient outcomes for women with ER+ breast cancer. Citation Format: Jerry T. DeWitt. Patient poverty burden influences the molecular biology of ER+ breast cancer [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr A042.