Background: Breast cancer is the most common cancer and the second leading cause of cancer-related mortality among U.S. women. Racial and ethnic disparities in breast cancer persist among Black, Hispanic, and certain Asian subgroups, including South Asian women, who have higher odds of advanced stage at diagnosis, more aggressive tumor subtypes, and poorer cancer outcomes than non-Hispanic White women. Substantial proportions of Hispanic and South Asian individuals in the U.S., and a smaller proportion of Black individuals in the U.S., are immigrants. Immigrant populations may have distinct cultural and lifestyle contexts that shape healthcare experiences and could contribute to breast cancer disparities. However, research on the role of culture-related factors, including acculturation, in shaping breast cancer disparities among U.S. women remains limited. Acculturation is a process through which immigrants adapt to the beliefs, behaviors, values, and social norms of U.S. society following migration. Objective and Specific Aims: This dissertation examined the role of acculturation across the breast cancer continuum among U.S. women through three specific aims: (1) to systematically review the literature on associations between acculturation and breast cancer risk factors, incidence, clinical presentation, treatment receipt, survivorship, and mortality among U.S. women; (2) to examine the association between acculturation and breast cancer stage at diagnosis among Black, Hispanic, and South Asian women in New Jersey, a diverse state in which these groups represent three of the largest racial and ethnic populations; and (3) to examine the association between acculturation and health-related quality of life among Black, Hispanic, and South Asian women in New Jersey. Methods: Aim 1 involved a systematic literature review based on searches of PubMed, Scopus, and Web of Science for English-language studies published from 1995 to 2024. Eligible manuscripts included studies of U.S. adult women that reported quantified associations between acculturation, assessed using proxy or scale-based measures, and breast cancer risk factors, incidence, clinical presentation, treatment receipt, survivorship, and mortality. Random-effects meta-analyses were used to pool adjusted estimates comparing immigrant and U.S.-born women for population-level breast cancer mortality and for individual-level breast cancer stage at diagnosis, and all-cause and breast cancer-specific mortality among women with breast cancer. Outcomes with fewer than five independent studies reporting adjusted effect estimates based on similar acculturation measures were not amenable to meta-analysis and were summarized descriptively. Aims 2 and 3 included Black and Hispanic breast cancer survivors from the New Jersey Breast Cancer Survivors (NJBCS) Study and South Asian breast cancer survivors from the Cancer Analytics and South Asian Health – Breast Cancer (CANSAH-BC) Study. These population-based survivorship cohorts administered identical structured questionnaires through in-home (NJBCS) or virtual (CANSAH-BC) interviews with women diagnosed with breast cancer in New Jersey from 2017 to 2023. In both aims, acculturation was assessed using percentage of life lived in the continental U.S., measured at the time of diagnosis in Aim 2 and at interview in Aim 3, and the Short Acculturation Scale for Hispanics (SASH) score at interview, derived using the SASH, which had been adapted for use across racial and ethnic groups. Both measures were modeled continuously and dichotomously using established thresholds. Aim 2 examined associations between acculturation and breast cancer stage at diagnosis in a pooled sample of Black, Hispanic, and South Asian women using multivariable logistic regression, with stage information obtained through linkage to the New Jersey State Cancer Registry. In separate logistic regression models among Hispanic women, multiplicative interaction between acculturation measures and neighborhood-level Hispanic enclave residence at diagnosis was also examined. Aim 3 examined associations between acculturation and self-reported health-related quality of life, measured using the Functional Assessment of Cancer Therapy – Breast (FACT-B) total score and five domain scores, each dichotomized at the pooled sample median. Multivariable robust Poisson regression was used to examine associations between acculturation and dichotomized FACT-B total score and each of the five domain scores in race- and ethnicity-stratified analyses. Among Hispanic women, multiplicative interaction between acculturation measures and neighborhood-level Hispanic enclave residence at diagnosis was also examined for the dichotomized FACT-B total score and each of the five domain scores. Results: In Aim 1, nativity was the predominant acculturation measure used across studies of acculturation and breast cancer among U.S. women. Other measures included generational status, age at U.S. migration, duration of U.S. residence, percentage of life lived in the U.S., and, in some studies, validated acculturation scales. Studies using nativity as an acculturation measure found that, compared with U.S.-born women, women born outside the U.S. had a lower prevalence of some breast cancer risk factors and lower population-level breast cancer incidence and mortality rates (pooled breast cancer mortality rate ratio MRR for foreign-born vs. U.S.-born women = 0.68, 95% CI: 0.63–0.73; n = 6; I² = 95%). However, among women with breast cancer, women born outside the U.S. tended to have higher odds of advanced stage at diagnosis compared with U.S.-born women, although the association was not statistically significant and heterogeneity was substantial (pooled odds ratio OR for advanced stage among foreign-born vs. U.S.-born women = 1.10, 95% CI: 0.99–1.22; n = 5; I² = 91%). Pooled estimates also did not indicate differences in all-cause or breast cancer-specific mortality after diagnosis between women born outside the U.S. and U.S.-born women, and between-study heterogeneity was substantial (pooled all-cause mortality hazard ratio HR for foreign-born vs. U.S.-born women = 1.05, 95% CI: 0.94–1.18; n = 7; I² = 94%; pooled breast cancer-specific mortality HR for foreign-born vs. U.S.-born women = 1.04, 95% CI: 0.93–1.16; n = 10; I² = 89%). In Aim 2, higher acculturation, measured using both proxy and scale-based measures, was consistently associated with lower odds of advanced breast cancer stage at diagnosis in the pooled sample of Black, Hispanic, and South Asian women diagnosed in New Jersey. For example, after adjustment for age at breast cancer diagnosis, year of diagnosis, race and ethnicity, marital status before diagnosis, socioeconomic factors before diagnosis, and reproductive and lifestyle factors before diagnosis, each 10 percentage-point increase in the percentage of life lived in the continental U.S. at diagnosis was associated with a 10% reduction in the odds of advanced breast cancer stage at diagnosis (OR = 0.90, 95% CI: 0.83–0.97). Among Hispanic women, no evidence of statistically significant multiplicative interaction between acculturation measures and neighborhood-level Hispanic enclave residence at diagnosis was observed. In Aim 3, no association was observed between acculturation measures and total FACT-B score or most FACT-B domains in race- and ethnicity-stratified models. However, among Hispanic women, significant multiplicative interaction was observed between acculturation measures, both percentage- and SASH-based, and Hispanic enclave residence at diagnosis for the social and family well-being (SFWB) domain. For example, among Hispanic women, after adjustment for age at breast cancer diagnosis, years since diagnosis, educational attainment, and breast cancer stage, higher acculturation, measured as a higher percentage of life lived in the continental U.S. at interview, was associated with better social and family well-being among those residing outside Hispanic enclaves (low SFWB PR for each 10 percentage-point increase = 0.88, 95% CI: 0.81–0.97), but not among those residing within enclaves (low SFWB PR for each 10 percentage-point increase = 0.99, 95% CI: 0.96–1.03; P-interaction = 0.017). Conclusion: Acculturation is an important sociocultural factor associated with breast cancer outcomes across the continuum, with associations that differ across individual- and population-level outcomes. However, most studies used nativity as a proxy measure of acculturation, which does not capture the complexity of the acculturation process. Comparability across studies was also limited by heterogeneity in study populations, acculturation measures, covariate adjustment sets, outcome definitions, and periods of observation. Additionally, most registry-based studies did not adjust for key confounders, such as income and insurance status, which are important for disentangling associations of acculturation proxies, such as nativity, from underlying sociodemographic differences. Additional studies using more comprehensive acculturation measures and more complete confounder adjustment are needed to better characterize the independent contribution of acculturation to breast cancer outcomes. Findings from this dissertation suggest that improving access to screening and early detection, particularly among less acculturated populations, and expanding culturally tailored survivorship support for Hispanic women across neighborhood contexts may be relevant strategies for addressing disparities in breast cancer presentation and survivorship among women in the United States.
Tina Amar Dharamdasani (Thu,) studied this question.
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