Breast cancer subtypes among Eastern-African-born black women and other black women in the United States.

Background: A previous study reported that Eastern-African-born black women in the United States had lower prevalence of estrogen receptor-negative breast cancer than those in US-born and Western-African-born black women, among whom the prevalence was similar. It is unknown whether the prevalence of triple-negative breast cancer (negative for estrogen receptor, progesterone receptor, and human epidermal growth factor 2 receptor) among black women in the United States differs similarly by birthplace.

Methods: In the National Program of Cancer Registries and US Cancer Statistics, the authors identified 65,211 non-Hispanic black women who were diagnosed with invasive breast cancer from 2010 through 2015 and were recorded as being born in the United States, East Africa, West Africa, or the Caribbean. The prevalence of triple-negative and hormone receptor-negative breast cancer (negative for estrogen receptor and progesterone receptor) among each group of foreign-born black women was compared with that among US-born black women and was expressed as the adjusted prevalence rate ratio, accounting for sociodemographic and tumor characteristics. Analyses were stratified by Census region, and region-specific estimates were summarized using random-effects meta-analyses.

Results: Compared with US-born black women, the prevalence rate ratio of triple-negative breast cancer was 0.92 (95% CI, 0.81-1.04) among Western-African-born, 0.87 (95% CI, 0.78-0.98) among Caribbean-born, and 0.53 (95% CI, 0.37-0.77) among Eastern-African-born black women. Patterns for hormone receptor-negative tumors were generally similar, although the differences between populations were attenuated. The test for heterogeneity by Census region was not significant in any of the comparisons (all P for heterogeneity >.05).

Conclusions: The prevalence of triple-negative breast cancer among black women in the United States varied significantly by birthplace, particularly among Eastern-African-born black women. These findings underscore the importance of considering geographic origin in studies characterizing breast cancer among women of African descent in the United States and elsewhere.