Survival rates of invasive breast cancer among ethnic Chinese women born in East Asia and the United States.

BACKGROUND: Few studies have compared the breast cancer survival rates of US born ethnic Chinese women and the survival rates of Chinese immigrants. The main purpose of this study is to explore the difference of breast cancer survival rates between the two populations and compare the survival rates to those of Caucasians born in the US.
METHODS: Between 1973 and 2002, 365,215 women who had been diagnosed with primary invasive breast cancer (ICD-O-2 C500:C509) were recorded in the Surveillance, Epidemiology, and End Results (SEER) registries. Of the 316,881 breast cancer patients who were white, 180,835 (57%) were born in the United States, 20,983 (7%) were born elsewhere, and 115,063 (36%) had unknown birthplaces. Among the 3,634 breast cancer patients who were ethnically Chinese, 952 (26%) patients were born in the US, 1,356 (37%) were born in East Asia, 146 (4%) were born elsewhere, and 1,180 (33%) had unknown birthplaces. We compared the survival rates and estimated the risk ratios (RRs) by the Kaplan-Meier estimates and the Cox proportional hazards models.
RESULTS: A lower 5-year overall survival rate of breast cancer was observed among Chinese women born in East Asia (0.74, 95% CI=0.72-0.77) than those born in the U.S. (0.79, 95% CI=0.76-0.81), with an adjusted hazards ratio of 1.22 (95% CI=1.06-1.40). The 5-year survival rates for SEER stage were higher among Chinese women born in the U.S. (localized: 0.90, 95% CI=0.87-0.93; regional: 0.71, 95% CI=66-0.77; distant: 0.16, 95% CI=0.06-0.25) than that among Chinese women born in East Asia (localized: 0.86, 95% CI=0.83-0.89; regional: 0.68, 95% CI=0.63-0.73; distant: 0.16, 95% CI=0.07-0.25). Higher 5-year survival rates among Chinese women born in the U.S. in comparison to Chinese women born in East Asia were also observed in different calendar years (1973-1980, 1981-1990, 1991-2002), in surgery and radiation therapy.
CONCLUSIONS: Our analysis showed that among the Chinese breast cancer patients, women born in East Asia had lower 5-year survival rates than women born in the United States. SEER stage, grade, and tumor size appear to be important prognostic factors. The poor 5-year survival rates among Chinese women born in East Asia indicate potential problems of accessing medical facilities for early detection, diagnosis and treatment because of potential language and culture barriers, lower education level, as well as stress of the first generation of migrant Chinese women in the United States.