Abstract B120: Neighborhood socioeconomic status and aggressive breast cancer subtypes in early-onset patients

Abstract

Early-onset breast cancer (BC)—commonly defined as diagnosis before age 40—is an important public health concern due to its rising incidence, stark racial disparities, and higher prevalence of more aggressive subtypes. Emerging evidence suggests neighborhood socioeconomic status (nSES) may be associated with BC subtype at diagnosis; however, little is known about this association among patients with early-onset BC, or whether it differs by race. This study examined the association between nSES and BC subtype at diagnosis among young women with BC in the U.S., overall and stratified by race. We identified adult non-Hispanic Black (NHB) and non-Hispanic White (NHW) women diagnosed with a first primary invasive BC before age 40 in the Surveillance, Epidemiology, and End Results (SEER)-17 database between 2010 and 2020. Neighborhood SES was measured using census tract-level Yost index quintiles, with Quintile (Q)1 reflecting the lowest SES group and Q5 the highest. BC subtype was approximated using hormone receptor (HR) and HER2 status, categorized as HR+/HER2− (Luminal A), HR+/HER2+ (Luminal B), HR−/HER2+ (HER2-enriched), and HR−/HER2− (triple negative breast cancer [TNBC]). Multivariable-adjusted logistic regression models were used to estimate odds ratios (OR) and 95% confidence intervals (CI) for the association between nSES and BC subtype, comparing Luminal B, HER2-enriched, and TNBC with Luminal A. Models included age at diagnosis, race/ethnicity (NHB, NHW), marital status (married, not married), urban/rural status, and year of diagnosis. Among 4,093 NHB and 13,953 NHW women with BC diagnosed before age 40, 31.1% resided in the highest nSES quintile and 13.8% in the lowest. Women residing in the lowest nSES quintile were more likely to be NHB, unmarried, live in rural areas, and be diagnosed with distant stage disease than the highest nSES group. Relative to women with the highest nSES (Q5), the odds of TNBC (vs. Luminal A) increased monotonically with decreasing nSES. The odds were 13% higher for Q4 (OR: 1.13; 95% CI: 1.01, 1.27), 18% higher for Q3 (OR: 1.18; 95% CI: 1.04, 1.34), 21% higher for Q2 (OR: 1.21; 95% CI: 1.06, 1.39), and 50% higher for women residing in the lowest nSES neighborhoods (Q1) (OR: 1.50; 95% CI: 1.31, 1.73). This pattern persisted among NHW women (Q1 vs. Q5: OR: 1.49; 95% CI: 1.24, 1.79) but was attenuated and less precise among NHB women (Q1 vs. Q5: OR: 1.28; 95% CI: 0.97, 1.70). There was no clear association for women with HER2-enriched or Luminal B cancers, with estimates largely null across nSES quintiles. Our findings suggest that lower nSES is associated with higher odds of TNBC, but not other breast cancer subtypes, among women with early-onset BC. This pattern was evident among NHW women, but attenuated among NHB women, potentially due to the higher baseline prevalence of TNBC in this group. These findings support further investigation into the mechanisms linking neighborhood deprivation to aggressive tumor biology among young women and across racial groups. Hyelim Shin, Sofia A. Oviedo, Lauren E. Barber, Lindsay J. Collin, Jacqueline B. Vo, Demetria J. Smith-Graziani, Lauren E. McCullough, Maret L. Maliniak . Neighborhood socioeconomic status and aggressive breast cancer subtypes in early-onset patients [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 B120.