Abstract A122: Breast cancer differences in incidence-based mortality by subtype, race and ethnicity, county-level population density, and median household income in the US, 2000-2023

Abstract

Breast cancer incidence and mortality rates (MRs) differ by estrogen receptor (ER) status; however, neighborhood determinants may exacerbate racial and ethnic breast cancer disparities. This study aimed to evaluate the intersection of race and ethnicity and county-level population density and income on ER positive and ER negative breast cancer mortality. We used SEER 17 cancer registries linked to US Mortality Data to estimate age-standardized incidence-based MRs per 100,000 person-years, parsing MRs by tumor characteristics. Analyses included women aged 30-84 years, who were diagnosed with invasive breast cancer from 2000–2023, and died from breast cancer within 10 years of diagnosis from 2009–2023. Incidence-based MR ratios (MRRs) compared American Indian/Alaska Native (AI/AN; N=593), Asian/Pacific Islander (API; N=7,222), Black (N=16,361), and Hispanic women (N=13,200), with White women (reference; N=61,879). All results were stratified by ER status (+/-), county-level population density (<250k; >250k-1 million; >1 million), and median household income quintiles (<$60k; $60k-$<$70k; $70k-<80k; $80k-<95k; >$95k). For ER+ breast cancer, Black women had the highest incidence-based MR (22.24; MRR=1.32; 95%CI=1.29,1.35), following by AI/AN (MR=17.86; MRR=1.06; 95%CI=0.96,1.17), White (MR=16.87; reference), Hispanic (MR=13.07; MRR=0.77; 95%CI=0.76,0.79), and API (MR=10.74; MRR=0.64; 95%CI=0.62,0.66). Black women had persistently elevated ER+ breast cancer mortality across all county stratifications, compared to White women (population density MRR range=1.23-1.33; income MRR range=1.22-1.38). However, AIAN women had higher ER+ breast cancer MRRs with greater population density (least dense MRR=0.90; 95%CI=0.76,1.06; most dense MRR=1.34; 95%CI=1.11,1.62) and wealthier counties (lowest income MRR=0.77; 95%CI=0.63,0.98; highest income MRR=1.60; 95%CI=1.34,1.91). For ER- breast cancer, Black women had the highest MR at 15.46 (MRR=2.32; 95%CI=2.25,2.39), more than double that of all racial and ethnic groups (MR range=4.43-7.76). Patterns were largely consistent by county-level population density and income for racial and ethnic groups, except for AI/AN women who again had higher ER- breast cancer MRRs with greater density (least dense MRR=0.70; 95%CI=0.53,0.93; most dense MRR=1.68; 95%CI=1.27,2.21) and wealthier counties (lowest income MRR=0.75; 95%CI=0.54,1.05; highest income MRR=1.95; 95%CI=1.47,2.58). In our study, Black women had consistently high ER+ and ER- breast cancer incidence-based MRs compared with all racial and ethnic groups regardless of residence at diagnosis, and AI/AN women had experienced higher incidence-based MRs in counties with greater population density and higher median household incomes, compared with White women. Findings were striking for ER+ breast cancer, where effective therapies are widely available and survival is generally favorable. The persistence of mortality disparities suggests that equitable access to cancer care remains unmet, even in high resource counties. Stephanie Ho, Paloma Mitra, Hyokyoung Hong, Jaimie Shing, Macy Corley, Lene Veiga, Quiera Booker, Jonine Figueroa, Meredith Shiels, Lauren McCullough, Amy Berrington de Gonzalez, Gretchen Gierach, Jacqueline Vo. Breast cancer differences in incidence-based mortality by subtype, race and ethnicity, county-level population density, and median household income in the US, 2000-2023 [abstract]. In: Proceedings of the 19th AACR Conference on the Science of Cancer Health Disparities; 2026 Oct 18-21; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2026;35(10 Suppl):Abstract nr A122.