Abstract A029: Age at menarche and risk of young-onset breast cancer subtypes overall and by race/ethnicity and socioeconomic position
Authors: Zhang Zhenzhen , Marcus Post Lydia R. , Pathak Dorothy R. , Hamilton Ann S. , Hirko Kelly A. , Houang Richard , Olson L. Karl , Schedin Pepper , Schwartz Ann G. , Velie Ellen M. 
Published: September 2024

Abstract
INTRODUCTION: Young-onset breast cancer (YOBC) (i.e., diagnosed &lt; 50 years), accounts for ∼25% of annual U.S. breast cancer (BC) cases, with incidence rates rising. Racial and socioeconomic disparities persist, with Non-Hispanic Black (NHB) women and residents of high-poverty areas facing a higher incidence of aggressive Estrogen Receptor-negative (ER-) BC tumors than Non-Hispanic White (NHW) and wealthier women. Early menarche is linked to increased BC risk, particularly for ER-positive (ER+) tumors, but its association with specific tumor subtypes and in young women is understudied. This study examines the association between age at menarche and YOBC tumor subtype risk among NHB and NHW women and whether race/ethnicity or socioeconomic position (SEP) modifies associations. METHODS: Data are from the Young Women’s Health History Study (YWHHS), a population-based case-control study of NHB and NHW women. Cases (n=1,812) included women diagnosed with invasive YOBC [luminal A, luminal B, HER2, triple-negative BC (TNBC) subtypes] in the Metropolitan Detroit and Los Angeles County SEER registry areas, 2010-15. Area-based controls (n=1,381) were identified from the 2010 Census and frequency matched to cases by study site, age, and race. Age at menarche (&lt;12, 12, 13, and ≥14 years) and covariates, including self-reported race (NHB/NHW) and SEP (&lt;200% vs. ≥200% of the federal poverty level), were assessed via in- person interviews. Multivariate weighted logistic regression was used to estimate YOBC tumor subtype risk and 95% confidence intervals (CIs) overall and stratified by race/ethnicity and SEP. RESULTS: Earlier age at menarche (&lt; 12 years) was more frequent among NHB (39.8%) than NHW (25.9%) women, and among poorer (37.0%) compared to wealthier (24.5%) women. Compared to menarche at age 13 years, menarche before age 12 years was associated with a higher risk of luminal A YOBC [adjusted odds ratio (aOR)=1.63, 95% CI, 1.17-2.27]. No significant associations were found for luminal B, HER2, or TNBC subtypes. Stratified by race/ethnicity, the increased risk of menarche before age 12 years for luminal A YOBC was significant only for NHW women [aOR=1.73, 95% CI, 1.15-2.60] and at 12 years for NHB women [aOR=1.91, 95% CI, 1.14-3.17] with no significant interaction (p=0.37). When stratified by SEP, menarche before age 12 years was consistently associated with increased risk for luminal A YOBC among both SEP &lt;200% [aOR=1.80, 95% CI, 1.04-3.11] and SEP ≥200% [aOR=1.74, 95% CI, 1.13-2.67] with no significant interaction (p=0.81). CONCLUSION: Our findings indicate that early menarche (&lt; 12 years) is associated with an increased risk of only luminal A YOBC, and risk was not significantly modified by race/ethnicity or SEP. Findings provide evidence that etiologic pathways related to age at menarche and BC risk differ by tumor subtypes in young women.
Citation Format: Zhenzhen Zhang, Lydia R. Marcus Post, Dorothy R. Pathak, Ann S. Hamilton, Kelly A. Hirko, Richard Houang, L. Karl Olson, Pepper Schedin, Ann G. Schwartz, Ellen M. Velie. Age at menarche and risk of young-onset breast cancer subtypes overall and by race/ethnicity and socioeconomic position [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 A029.