Abstract 4949: Late-stage breast cancer risk and five-year survival by stage at diagnosis among top 5 Asian ethnic subgroups in California

Abstract Introduction: Breast cancer (BC) incidence over the past decade has been rapidly increasing among Asian American (AA) women compared to non-Hispanic White (NHW) women. AA women are more likely to be diagnosed with BC at an earlier stage and have better survival compared to Hispanic and Black women. However, the aggregation of AA may conceal significant population heterogeneity and health disparities among ethnic subgroups, as the risk profile in one subgroup differ from another. Thus, we aimed to understand AA ethnic disparities in BC by assessing AA subgroups and their relationship with late-stage diagnosis and all-cause mortality by stage at diagnosis using a cohort of AA BC patients from the California Cancer Registry (CCR). Methods: We identified BC cases among NHW and among the top 5 AA subgroups (Chinese, Japanese, Filipino, Korean, and Vietnamese) diagnosed in California between 1988 to 2020 using the CCR. We conducted multivariable logistic regression to evaluate the association between the odds of being diagnosed with late-stage BC (regional and distant stages) and AA subgroups. Additionally, 5-year observed survival rates across each AA subgroup were calculated at each stage at diagnosis (in situ or localized, regional, and distant). Lastly, we conducted multivariable Cox proportional hazards regression to assess all-cause mortality by AA subgroups. All models were adjusted for year at diagnosis, age at diagnosis, nativity, socioeconomic status (SES), comorbidity, insurance status, and BC subtype. We used NHW as the reference group. Results: Our sample contained a total of 557,551 BC cases (NHW N=493,227; Chinese N=19,380; Japanese N=8,893; Filipino N=24,938; Korean N=5,075; Vietnamese N=6,038). We found that Chinese, Japanese, Korean, and Vietnamese women were less likely to be diagnosed with late-stage BC compared to NHW (p<0.01 for Chinese, Japanese, and Vietnamese; p=0.02 for Korean), while no difference was observed for Filipino women (p=0.72). When comparing the 5-year observed survival rates from all causes of death by stage at diagnosis, all 5 AA subgroups had higher 5-year survival compared to NHW across all stages. However, when adjusted for year at diagnosis, age at diagnosis, nativity, SES, comorbidity, insurance status, and BC subtype, Chinese women diagnosed at the distant stage were 25% more likely than NHW women to die from all causes (p<0.01). Conclusions: Most AA subgroups were at lower odds of being diagnosed with late-stage BC compared to NHW, except for Filipino women. Survival outcomes also differed by subgroups and by stage at diagnosis. Differences in AA subgroups could be due to several factors (i.e., social factors, environmental factors). Thus, different cancer strategies in terms of cancer control and care improvement for each group are needed. Citation Format: Michelle Tran, Kimberly A. Miller, Sue E. Kim, Kali Zhou, Myles Cockburn, Lihua Liu. Late-stage breast cancer risk and five-year survival by stage at diagnosis among top 5 Asian ethnic subgroups in California [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4949.