Disparities in Breast Cancer Survival Among Asian Women
Disparities in Breast Cancer Survival Among Asian Women
Objectives. We investigated heterogeneity in ethnic composition and immigrant status among US Asians as an explanation for disparities in breast cancer survival.
Methods. We enhanced data from the California Cancer Registry and the Surveillance, Epidemiology, and End Results program through linkage and imputation to examine the effect of immigrant status, neighborhood socioeconomic status, and ethnic enclave on mortality among Chinese, Japanese, Filipino, Korean, South Asian, and Vietnamese women diagnosed with breast cancer from 1988 to 2005 and followed through 2007.
Results. US-born women had similar mortality rates in all Asian ethnic groups except the Vietnamese, who had lower mortality risk (hazard ratio [HR]=0.3; 95% confidence interval [CI]=0.1, 0.9). Except for Japanese women, all foreign-born women had higher mortality than did US-born Japanese, the reference group. HRs ranged from 1.4 (95% CI=1.2, 1.7) among Koreans to 1.8 (95% CI=1.5, 2.2) among South Asians and Vietnamese. Little of this variation was explained by differences in disease characteristics.
Conclusions. Survival after breast cancer is poorer among foreign- than US- born Asians. Research on underlying factors is needed, along with increased awareness and targeted cancer control
Breast cancer incidence rates have been shown to differ markedly across distinct ethnic subpopulations of US Asian women, and studies of outcomes after breast cancer similarly have detected wide variation in stage at diagnosis and survival patterns across groups. For example, in a population-based study, we reported that 5-year survival probabilities and proportions of late-stage disease were as poor in Filipinas as in African American women and that Japanese women had more favorable stage and survival distributions than did non-Hispanic White women. Identifying and explaining such disparities are important for public health efforts to diminish disparities in outcomes after breast cancer. However, explanations for the ethnic differences in breast cancer survival in Asians have not been carefully studied aside from the effects of variations in treatment, sociodemographic factors, and tumor characteristics.
Asian populations in the United States are heterogeneous with respect to immigration and acculturation, 2 factors likely to play a substantial role in explaining different outcomes. However, initial efforts to examine the impact of these factors have been hampered by gaps in population-based data. Birthplace is missing for a substantial proportion (approximately 25%) of cancer patients reported to the National Cancer Institute's Surveillance, Epidemiology, and End Results Program, and patients with missing information are more likely to be US than foreign born. The resulting bias may have skewed the results of previous examinations of the association between immigration status and breast cancer stage and survival and obscured understanding of how immigration influences ethnic disparities in survival. Degree of Western acculturation is not assessed by cancer registries for immigrant patients, although it may have independent effects on treatment and other factors affecting health outcomes among Asians.
To advance the effort to reduce breast cancer disparities in Asian women, we enhanced population-based cancer registry data to enable the examination of the effects of individual- and neighborhood-level factors on the associations with survival after breast cancer diagnosis among Chinese, Japanese, Filipina, Korean, South Asian, and Vietnamese women in California. We enhanced the data in 2 ways: (1) we used a novel method for statistically imputing immigrant status by age at assignment of Social Security number (SSN) to designate nativity where that information was missing, and (2) we linked registry data to US Census data to incorporate neighborhood factors characterizing Asian ethnic enclave and socioeconomic status (SES) in our analyses. We defined a neighborhood ethnic enclave as a geographical unit with a greater concentration of Asian population and speakers of Asian languages than other geographical units in California. With this enhanced registry resource, we examined whether individual-level immigrant status, neighborhood-level ethnic enclave, and SES explain differences in survival after breast cancer diagnosis within and across Asian ethnic groups.
Abstract and Introduction
Abstract
Objectives. We investigated heterogeneity in ethnic composition and immigrant status among US Asians as an explanation for disparities in breast cancer survival.
Methods. We enhanced data from the California Cancer Registry and the Surveillance, Epidemiology, and End Results program through linkage and imputation to examine the effect of immigrant status, neighborhood socioeconomic status, and ethnic enclave on mortality among Chinese, Japanese, Filipino, Korean, South Asian, and Vietnamese women diagnosed with breast cancer from 1988 to 2005 and followed through 2007.
Results. US-born women had similar mortality rates in all Asian ethnic groups except the Vietnamese, who had lower mortality risk (hazard ratio [HR]=0.3; 95% confidence interval [CI]=0.1, 0.9). Except for Japanese women, all foreign-born women had higher mortality than did US-born Japanese, the reference group. HRs ranged from 1.4 (95% CI=1.2, 1.7) among Koreans to 1.8 (95% CI=1.5, 2.2) among South Asians and Vietnamese. Little of this variation was explained by differences in disease characteristics.
Conclusions. Survival after breast cancer is poorer among foreign- than US- born Asians. Research on underlying factors is needed, along with increased awareness and targeted cancer control
Introduction
Breast cancer incidence rates have been shown to differ markedly across distinct ethnic subpopulations of US Asian women, and studies of outcomes after breast cancer similarly have detected wide variation in stage at diagnosis and survival patterns across groups. For example, in a population-based study, we reported that 5-year survival probabilities and proportions of late-stage disease were as poor in Filipinas as in African American women and that Japanese women had more favorable stage and survival distributions than did non-Hispanic White women. Identifying and explaining such disparities are important for public health efforts to diminish disparities in outcomes after breast cancer. However, explanations for the ethnic differences in breast cancer survival in Asians have not been carefully studied aside from the effects of variations in treatment, sociodemographic factors, and tumor characteristics.
Asian populations in the United States are heterogeneous with respect to immigration and acculturation, 2 factors likely to play a substantial role in explaining different outcomes. However, initial efforts to examine the impact of these factors have been hampered by gaps in population-based data. Birthplace is missing for a substantial proportion (approximately 25%) of cancer patients reported to the National Cancer Institute's Surveillance, Epidemiology, and End Results Program, and patients with missing information are more likely to be US than foreign born. The resulting bias may have skewed the results of previous examinations of the association between immigration status and breast cancer stage and survival and obscured understanding of how immigration influences ethnic disparities in survival. Degree of Western acculturation is not assessed by cancer registries for immigrant patients, although it may have independent effects on treatment and other factors affecting health outcomes among Asians.
To advance the effort to reduce breast cancer disparities in Asian women, we enhanced population-based cancer registry data to enable the examination of the effects of individual- and neighborhood-level factors on the associations with survival after breast cancer diagnosis among Chinese, Japanese, Filipina, Korean, South Asian, and Vietnamese women in California. We enhanced the data in 2 ways: (1) we used a novel method for statistically imputing immigrant status by age at assignment of Social Security number (SSN) to designate nativity where that information was missing, and (2) we linked registry data to US Census data to incorporate neighborhood factors characterizing Asian ethnic enclave and socioeconomic status (SES) in our analyses. We defined a neighborhood ethnic enclave as a geographical unit with a greater concentration of Asian population and speakers of Asian languages than other geographical units in California. With this enhanced registry resource, we examined whether individual-level immigrant status, neighborhood-level ethnic enclave, and SES explain differences in survival after breast cancer diagnosis within and across Asian ethnic groups.
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