Abstract PS7-39: Survival differences in chinese versus white women with breast cancer in the United States: A SEER-based analysis
Authors: Lim David Wai , Giannakeas Vasily , Narod Steven A 
Published: February 2021

Abstract
Purpose: Several studies have reported lower breast cancer survival rates among Black women compared to White women, but less is known regarding outcomes in Chinese women. We compared survival rates for Chinese and White women with breast cancer in the Surveillance, Epidemiology, and End Results (SEER) database diagnosed between 2004 and 2015.
Methods: We conducted a cohort study of Chinese and White women with breast cancer diagnosed between 2004 to 2015 in the SEER18 registries database. We abstracted information on age and year of diagnosis, marital status, median household income, tumour size and grade, lymph node status, clinical stage, receptor status (estrogen, progesterone, and HER-2/neu receptor), surgical treatment (lumpectomy versus mastectomy), receipt of radiotherapy and chemotherapy, and death. Chinese and White women were compared for demographic, pathologic and treatment variables and differences were assessed using standardized differences. Our primary outcome was death from breast cancer. We compared crude breast cancer-specific mortality rates between the two ethnic groups. We also calculated adjusted hazard ratios (HR) in a propensity-matched design using the Cox proportional hazards model. Women were matched on the year of diagnosis and age at diagnosis (both within 2 years), tumour grade, nodal status, clinical stage, estrogen receptor status, HER2/neu status and propensity score. The propensity score accounted for marital status, household income, tumour size, progesterone receptor status and surgical procedure. A log-rank test was used to compare differences between groups using the Kaplan-Meier method. P values &lt; .05 were considered statistically significant.
Results: There were 7,553 Chinese women (1.8%) and 414,618 White women (98.2%) with stage I-IV breast cancer registered in the SEER database. There were only small differences in tumour size, stage at presentation, node-positivity, the proportion of HER2-positive cancers, and the treatments received. Among women with stage I-IIIC breast cancer, 10-year breast cancer-specific survival was 88.8% for Chinese women, compared with 85.6% for White women. The cumulative mortality from breast cancer after 11 years of follow-up was 12.9% for Chinese women and 16.4% for White women; crude HR 0.73 (95% CI 0.67 - 0.80; P &lt; .0001). In the first nine years after diagnosis, annual mortality rates are higher in White women than for Chinese women. Following the first nine years after diagnosis, the annual mortality rate for Chinese women then exceeds that of White women. In a propensity-matched analysis, the cumulative mortality from breast cancer after 11 years of follow-up was 8.9% for Chinese women and 11.9% for White women (P = .0002). The adjusted hazard ratio was 0.71 (95% CI 0.62 - 0.81) and was similar to the crude hazard ratio of 0.73 (95% CI 0.67 - 0.90). The adjusted hazard ratios demonstrate that Chinese women had better survival than White women in subgroups defined by age of diagnosis, tumour size and grade, clinical stage, nodal status and estrogen receptor status. The largest effects were observed for stage I cancers (HR 0.57, 95% CI 0.36-0.90) and for node-negative cancers (HR 0.61, 95% CI 0.46-0.82).
Conclusion: Chinese women diagnosed with breast cancer in the SEER database between 2004 to 2015 had significantly better survival rates than White women with breast cancer. Over a 10-year follow-up period, Chinese women with stage I-IIIC breast cancer experienced a 30% lower risk of death than a comparable group of White women with breast cancer. The observed difference cannot be accounted for by clinical presentation or by differences in treatment and suggests that there are intrinsic biological differences in breast cancer between Chinese and White women.
Citation Format: David Wai Lim, Vasily Giannakeas, Steven A Narod. Survival differences in chinese versus white women with breast cancer in the United States: A SEER-based analysis [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-39.