Abstract 3627: Looking beyond the aggregate: uncovering ethnic-specific differences in breast cancer among young Asian American women

Background: Emerging data suggest that breast cancer incidence rates in Asian American women are on the rise, and this has also been observed specifically among young women (i.e., under age 40). However, most breast cancer studies often aggregate data across all Asian Americans, overlooking the distinct sociodemographic features and health disparities that may characterize each Asian ethnic subgroup. Therefore, it is unclear if the observations noted in young Asian American breast cancer patients as a single group translate to each Asian subgroup as well. This is especially important when it comes to young women since they do not have established breast cancer screening guidelines and are more likely to be diagnosed with advanced stage tumors. Methods: We analyzed the Surveillance, Epidemiology, and End Results Program’s (SEER’s) specialized Asian groups database, which includes cancer incidence data from 13 population-based registries. Overall, 33,960 female breast cancer cases who were diagnosed under age 40 and between the years of 1990 and 2014 were identified; the 1990-2014 time period for our analysis reflects the available data in this database. We calculated incidence rate ratios (IRRs) and 95% confidence intervals (CIs) comparing young breast cancer incidence by stage for seven Asian subgroups relative to Non-Hispanic Whites (NHWs). Joinpoint regression models were also run to determine annual percent change (APC) using 5-year grouping intervals for the racial/ethnic groups. Results: Most Asian ethnic subgroups showed lower incidence rates of regional/distant breast cancer when compared to NHWs with the only exception being Hawaiian/Pacific Islanders (IRR=1.14, 95% CI 0.98-1.31). Regional/distant breast cancer incidence had also been trending upwards for most racial/ethnic groups; it increased 2.72% for Asian Indian/Pakistanis (95% CI -0.52 to 7.61) and 1.97% for Koreans (95% CI 0.79 to 3.18). Japanese constituted the only Asian subgroup to be significantly more likely to receive a localized breast cancer diagnosis relative to NHWs (IRR=1.21, 95% CI 1.09-1.35). In addition, significant increasing trends of localized tumors were observed for Asian Indian/Pakistanis (APC=3.35, 95% CI 1.20 to 6.71) and Chinese (APC=1.18, 95% CI 0.23 to 2.23). Conclusions: Breast cancer in young women is understudied, particularly in Asian Americans who have historically been thought to be at lower risk of the disease. With the growing literature highlighting the increasing incidence of breast cancer in Asian Americans, including young women, our findings highlight important disparities in which specific ethnic subgroups appear to be at higher burden of advanced stage breast cancer. This type of work is essential for developing targeted preventive strategies to address the needs of young Asian females. Citation Format: Alice W. Lee, Diana Aguilar-Cruz, Cindy Do, Peyton Fisher, Aleah La Flair, Mojgan Sami, Nicole Wells. Looking beyond the aggregate: uncovering ethnic-specific differences in breast cancer among young Asian American women [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 3627.