Abstract C045: Impact of county-level income and rurality on cardiovascular disease mortality among women with ductal carcinoma in situ of the breast

Abstract Background: While associations of county-level household income and rurality with cardiovascular disease (CVD) mortality have been reported among women with invasive breast cancer, it is unknown if these associations also exist among women diagnosed with ductal carcinoma in situ (DCIS) of the breast. Methods: We identified 158,072 women diagnosed with DCIS between 2000-2018 from 17 Surveillance, Epidemiology, and End Results registries (age 20-84 years, survived 12+ months, and did not receive chemotherapy). Our primary exposures were county-level median household income from the US Census Bureau’s American Community Survey ($<50,000; $50,000-<$60,000; $60,000-<$70,000; $70,000-<$75,000; $≥75,000) and rurality based on rural-urban continuum codes developed by the US Department of Agriculture (rural not adjacent to metropolitan area; rural adjacent to metropolitan area; urban <250,000 residents; urban 250,000 to 1 million residents; urban >1 million residents). Median income and rurality were based on county of residence at DCIS diagnosis. Our primary outcomes were mortality due to 1) CVD (International Classification of Diseases (ICD)-10 codes I00-I13, I20-I51, I60-I78); 2) heart disease (I00-I09, I11, I13, I20-I51); and 3) cerebrovascular disease (I60-I69). We used Fine and Gray regression to estimate subdistribution hazard ratios (HRs) adjusting for age, diagnosis year, surgery type, and radiotherapy. We further examined results among non-Hispanic Black and non-Hispanic White women, but we were unable to examine results among other racial and ethnic groups due to small sample size. Results: Over 7.4 median years of follow-up, 4,504 women diagnosed with DCIS died from CVD (3,190 heart disease; 964 cerebrovascular disease). Women living in the poorest counties at DCIS diagnosis had a higher risk of CVD mortality compared to those living in the wealthiest counties (HR$<50,000=1.35, 95%CI=1.23-1.49), and risk decreased with increasing county-level income (p-trend<.001). Risk of CVD mortality was higher for women living in rural and small metropolitan counties than women living in the most urban counties (HRrural not metropolitan adjacent=1.20, 95%CI=1.04-1.38; HRrural metropolitan adjacent=1.17, 95%CI=1.04-1.31; HRmetropolitan <250,000 residents=1.25; 95%CI=1.12-1.38). Results for heart disease and cerebrovascular disease mortality were overall similar but attenuated for rurality and cerebrovascular disease. Disparities for county-level income and rurality persisted among non-Hispanic Black and non-Hispanic White women (HRs range: 1.15-1.30). Conclusions: Women living in poor and rural to small urban counties at DCIS diagnosis had a significantly higher risk of CVD mortality than those residing in urban or wealthier counties. Additional research is needed to understand the barriers driving these disparities and to identify the most effective methods to mitigate CVD sequela among women with DCIS. Our findings, however, are consistent with the idea that poverty may be an underlying driver of CVD mortality in women with DCIS. Citation Format: Ziad Zakaria, Geetanjali D. Datta, Lene HS Veiga, Amy Berrington de González, Jacqueline B. Vo, Cody Ramin. Impact of county-level income and rurality on cardiovascular disease mortality among women with ductal carcinoma in situ of the breast [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 C045.