DOI: 10.25549/usctheses-c40-365517
title: Relationship between traditional breast cancer risk factors and difference of breast cancer incidence rates among Chinese Americans, Japanese Americans and Filipina Americans

description: Background: Breast cancer is the most common type of cancer among females. Asian women experience a lower incidence of breast cancer than in Western populations. However, Filipina Americans have exceptionally high breast cancer incidence rates among Asian Americans. Lacking relevant evidence, the reasons contributing to differences in incidence rates of breast cancer between Filipina American and other Asian ethnicities remain unknown. Hence, to further study the factors that contributed to the difference, we analyzed the data from a population based case control study among Chinese American, Japanese American, and Filipina American in Los Angeles County. ❧ Methods: Breast cancer diagnosed in Chinese, Japanese, and Filipina American women were identified by the Los Angeles County Cancer Surveillance Program and controls were identified from the same neighborhood of the cases and were matched to cases on age and ethnicity. A conditional logistic regression predictive model was developed using the data from the case‐control study. With the predictive model, baseline breast cancer incidence rates after adjusting for the significant traditional breast cancer risk factors in this study for each of these three Asian ethnicities were calculated. The resulting covariate-adjusted baseline incidence rates were obtained by equalizing the age‐adjusted expected incidence rates of the predictive model to the population age‐adjusted breast cancer incidence rates in the corresponding period of time. ❧ Results: In total, there were 4,173 subjects in the study to be analyzed (1,983 cases, 2,190 controls). We developed a predictive model that included seven statistically significant breast cancer risk factors: years of residence in the U.S., household income, family history of breast cancer, history of benign breast disease, number of births, cumulative menstrual months, and weight gain since age 18. With the predictive model, baseline breast cancer incidence rates (per 100,000 person-year) after adjusting for the distribution of significant risk factors for each of the three Asian ethnicities were 65.16 among Chinese, 99.22, among Japanese, and 84.53 among Filipina American. Compared with the breast cancer incidence rates among Asian American populations in the United States, the rate ratios between Chinese American and Filipina American were similar, 0.76 and 0.77 (Filipina American as reference group), while the rate ratios between Filipina American and Japanese American were higher, 1.01 versus 1.17 (Filipina American as reference group). The differences in incidence rates of breast cancer among the three Asian ethnicities were not eliminated, after adjusting for the distribution of the significant traditional breast cancer risk factors identified from this case‐control study in Los Angeles County. ❧ Conclusion: This analysis suggests that the differences in distributions of the significant traditional breast cancer risk factors identified from the case‐control study were not sufficient to explain the differences in incidence rates of breast cancer between Chinese‐, Japanese‐, and Filipina‐American women.