Abstract B26: Individual- and neighborhood-level immigration factors and breast cancer risk among Latinas in the San Francisco Bay Area: The Neighborhoods and Breast Cancer (NABC) Study

Among U.S. Latinas, breast cancer risk is lower among foreign-born than U.S.-born women; however, after adjustment for known risk factors, the association remained in post-menopausal women only. To evaluate the extent to which breast cancer risk among Latinas may be affected by neighborhood characteristics, we examined the independent and joint associations of individual-level (nativity, language use, generational status, percent of life in U.S.) and neighborhood-level (residence in ethnic enclave) immigration factors with breast cancer risk in 1401 Latina cases and 1074 Latina controls pooled from two population-based San Francisco Bay Area studies. Ethnic enclaves refer to areas that maintain more Latino cultural mores and are ethnically distinct from the surrounding area. Block group-level measures of socioeconomic status (SES) and ethnic enclave are based on indices comprising multiple Census 2000 measures, and developed via principal components analyses. Unconditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI), with adjustment for relevant confounders and block group clustering. Among pre-menopausal women, we identified a synergistic effect between individual- and neighborhood-level immigration factors. Compared to U.S.-born Latinas living in low ethnic enclaves (i.e., less ethnic), foreign-born Latinas in high enclaves (i.e., more ethnic) had a lower risk of breast cancer, which was attributable primarily to differences in reproductive risk factors (age at menarche, parity, breastfeeding, age at first birth), education, and neighborhood SES. There was also a synergistic effect between neighborhood SES and ethnic enclave, with the reduction in breast cancer risk greatest among women in high SES and high enclave neighborhoods [OR (95% CI) = 0.30 (0.15-0.60)] compared to women living in high SES and low enclave neighborhoods. Risk reductions were more moderate among those in low SES neighborhoods and similar across ethnic enclave status [low SES/high enclave OR = 0.64 (0.41-1.01); low SES/low enclave OR = 0.60 (0.41-0.86), compared to high SES/low enclave]. Similar patterns of synergistic effects were found among post-menopausal women. Compared to U.S.-born Latinas living in low enclaves, foreign-born Latinas in high enclaves had a considerably lower risk of breast cancer [OR (95% CI) = 0.41 (0.28-0.61)], while the moderate risk reductions among U.S.-born Latinas living in high enclaves and foreign-born in low enclaves were no longer statistically significant after adjusting for behavioral and reproductive risk factors. Neighborhood SES had a stronger effect on breast cancer risk than ethnic enclave. Compared to those living in high SES and low enclave neighborhoods, ORs were similar for low SES/low enclave [OR=0.65 (0.45-0.93)] and low SES/high enclave [OR=0.53 (0.39-0.71)]. Our results suggest that, even after accounting for individual-level factors, the SES and ethnic/acculturation level of neighborhoods play an important role in influencing breast cancer risk among Latinas. Risk among Latinas is lower in more ethnic and lower SES neighborhoods, although among pre-menopausal women, the ethnic enclave effect appears to be explained by reproductive factors. Identifying the specific aspects of these neighborhoods (e.g., more built environment, social support /networks, ethnic foods) that Latina women reside in may provide insights into breast cancer risk factors, and strategies for risk reduction. Citation Format: Scarlett Lin Gomez, Salma Shariff-Marco, Juan Yang, Meera Sangaramoorthy, Theresa H.M. Keegan, Jocelyn Koo, Clayton Schupp, Andrew Hertz, David O. Nelson, Esther M. John. Individual- and neighborhood-level immigration factors and breast cancer risk among Latinas in the San Francisco Bay Area: The Neighborhoods and Breast Cancer (NABC) Study. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr B26. doi:10.1158/1538-7755.DISP13-B26