Abstract C040: Racial and ethnic differences in breast cancer prognosis and survival in a multiethnic cohort of Asian American breast cancer patients compared with non-Latina White patients at Kaiser Permanente Northern California

Abstract Background: In the U.S., breast cancer (BC) survival differs significantly by race and ethnicity, with Asian American (AA) patients consistently showing more favorable survival relative to other racial and ethnic groups. Factors contributing to the survival advantage of AA females, a heterogeneous population, are unknown. Methods: We included 5,294 AA female patients diagnosed with incident AJCC stage I-IV BC from 2000-2015 at Kaiser Permanente Northern California, and a random sample of 5,294 non-Latina White (NLW) patients. Follow-up was through 12/31/2020 for recurrence, second primary cancer, BC death, and all-cause death. Survival analysis was conducted using multivariable, cause-specific Cox proportional hazards models. Results: The AA cohort consisted of 41% Filipina, 27% Chinese, 9% Japanese, 9% South Asian, 7% Other Asian, 3% Korean, and 5% Southeast Asian females. AA and NLW females had similar stage (12% III/IV) and ER/PR status (15-18% ER-/PR-), yet more AA females were diagnosed with HER2+ or borderline disease (19% vs. 14%). More AA females had chemotherapy (48% vs. 39%) and mastectomy (47% vs. 36%) with less radiation therapy (38% vs. 46%) than NLW females. Receipt of endocrine therapy was similar between AA and NLW females (72-73%). Compared with NLW females, AA females were younger (mean=56.9 vs. 63.2 years), lived in higher SES neighborhoods (census tract-level education and income), had no comorbidities (45% vs. 36%), lower BMI (mean=25.5 vs. 28.6 kg/m2), and were never smokers (77% vs. 50%) at diagnosis. Fewer AA vs. NLW females met national guidelines of 150 minutes/week of moderate-vigorous exercise (27% vs. 33%). In multivariable Cox models adjusted for diagnosis year, diagnosis age, stage, ER/PR and HER2 status, chemotherapy, radiation therapy, endocrine therapy, and surgery type, AA females had 20% lower risk of BC death and all-cause death compared with NLW females. Similar lower risks were seen across AA ethnicities. Specifically, Japanese and Chinese females had lower risks of BC death (hazard ratio, HR=0.66; 95% confidence interval, CI: 0.47-0.93 and HR=0.78; 95% CI: 0.63-0.97) and all-cause death (HR=0.67; 95% CI: 0.53-0.84 and HR=0.78; 95% CI: 0.67-0.92). South Asian females also had lower risk of all-cause death (HR=0.71; 95% CI: 0.53-0.96). AA females had 17% lower risk of second primary cancer compared with NLW females, specifically for Japanese, South Asian, and Other Asian females (HR range: 0.60-0.66). No difference in risk of recurrence was observed for AA vs. NLW females (HR=1.08; 95% CI: 0.90-1.29), including by Asian ethnicities. Conclusions: In this large, multiethnic cohort in an integrated health care system, clear differences in sociodemographic, clinical, and lifestyle factors exist between AA and NLW BC patients. After accounting for these factors, AA females had a survival advantage over NLW females, mostly in Japanese, South Asian, and Chinese females. These findings identify contributors to outcomes that may be specific to Asian ethnicities and can inform improving survival in all BC patients. Citation Format: Marilyn , Lia D'Addario, Janise Roh, Isaac Ergas, Catherine Lee, Salma Shariff-Marco, Iona Cheng, Valerie McGuire, Julie Von Behren, Katherine Lin, Esperanza Castillo, Mi-Ok Kim, Esther John, Anna Wu, Lenora Woo, Allison Kurian, Angela Omilian, Christine Ambrosone, Song Yao, Scarlett Gomez, Lawrence Kushi. Racial and ethnic differences in breast cancer prognosis and survival in a multiethnic cohort of Asian American breast cancer patients compared with non-Latina White patients at Kaiser Permanente Northern California 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 C040.