Abstract D094: Associations among state-level racial inequality, individual-level unfair treatment, and incident breast cancer in a risk-enriched cohort
Authors: Linnenbringer Erin , Humble Sarah , Gehlert Sarah , Sandler Dale P 
Published: September 2020

Abstract
Background: There is a small but growing body of evidence suggesting that structural inequality is associated with racial disparities in breast cancer stage at diagnosis and mortality. Less is known about the potential relationship between structural inequality and breast cancer incidence or subtypes. To address this gap, we developed a multidimensional state-level measure of racial inequality and assessed whether higher levels of inequality are associated with 1) higher odds of an invasive breast cancer diagnosis, and 2) among those diagnosed, higher odds of an estrogen receptor negative (ER-) vs. positive (ER+) tumor. Methods: The Sister Study is a longitudinal cohort of women who had a sister diagnosed with breast cancer, but did not have a personal history of the disease at enrollment. Leveraging this cohort, we generated state-level composite scores (range = 1-5) summarizing differences between non-Hispanic white and black residents across four domains: educational attainment, employment & occupational status, political participation, and incarceration. Data for the racial inequality measure were drawn from publicly available sources and linked to the participants’ state of residence at the time of enrollment. An individual-level measure of unfair treatment due to race was included as a proximal exposure to racial inequality. Invasive breast cancer diagnoses and subtypes were recorded through September 2016. The final analytic sample was limited to non-Hispanic white (n= 38,760) and black (n=4,061) Sister Study participants and their states of residence (n=40). Two-level population average models were constructed to assess the relationship among state- and individual-level factors and the odds of 1) an invasive breast cancer diagnosis (n=1,475) and 2) ER subtype among women with invasive breast cancer (1,278 ER+ cases; 197 ER- cases). Results: Adjusting for self-reported race, education, age, and epidemiologic risk factors (e.g., breast feeding history, menopausal status), we found that women residing in states with higher levels of racial inequality did not have higher odds of invasive breast cancer. However, among women diagnosed with an invasive breast cancer, we found higher odds of ER- vs. ER+ subtype among women living in states with higher levels of racial inequality (OR range = 1.7 – 2.6 for inequality composite scores of 3-5 vs. 1; p-values of &lt;0.001 to 0.04). The proximal measure of unfair treatment due to race was also a significant factor in the fully-adjusted model, with women reporting 2 or more incidents of unfair treatment having a 2.6 times higher odds of an ER- diagnosis than women reporting no such incidents. Conclusions: In this relatively small sample of invasive breast cancer cases, structural and interpersonal experiences with racial inequality were associated with greater odds of the ER- vs. ER+ subtype, but not with the overall odds of an invasive breast cancer diagnosis. Reanalysis using a longer follow-up period may provide greater insight into this novel association.
Citation Format: Erin Linnenbringer, Sarah Humble, Sarah Gehlert, Dale P Sandler. Associations among state-level racial inequality, individual-level unfair treatment, and incident breast cancer in a risk-enriched cohort [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 D094.