Breast Cancer Incidence Rates in Ghanaian and US Black Women from 2013 Through 2015

Importance: Uncertainty exists about whether women of West African ancestry have increased rates of estrogen receptor (ER)-negative breast tumors, which commonly have earlier age onsets than ER-positive tumors and are aggressive. High-quality population-based studies in Africa with tumor pathology data are generally unavailable, and there is speculation that younger population age structures may explain the increased frequencies of reported ER-negative tumors. Objective: To estimate age-standardized and age-specific rates of ER-negative breast cancer among Ghanaian women and non-Hispanic Black and non-Hispanic White women in the US. Design, Setting, and Participants: This cross-sectional study used 2013 through 2015 data from a population-based case-control study conducted in 2 metropolitan areas of Ghana, Accra and Kumasi, to estimate ER-specific breast cancer incidence rates among women 18 to 74 years of age. Incidence rates were recovered by applying sampling weights for controls calculated by district, 5-year age groups, and nonresponse rates from the 2010 census-based enumeration area listings. US Breast Cancer Registry data were retrieved from 17 registries in the Surveillance, Epidemiology, and End Results (SEER) program for non-Hispanic Black and non-Hispanic White women with breast cancer 20 to 74 years of age. Analyses were conducted January 2020 through May 2025. Exposures: Age, sex, race and ethnicity, ER tumor status, and country (US and Ghana). Main Outcomes and Measures: For each of 3 populations, crude, age-standardized, and age-specific breast cancer incidence rates were calculated overall and by ER status. Results: Analyses were performed for 1071 women (age range, 18-74 years; 468 [51%] ER-negative) in Ghana and 18321 non-Hispanic Black women (age range, 20-74 years; 5117 [29%] ER-negative) and 103227 non-Hispanic White women (age range, 20-74 years; 15040 [15%] ER-negative) in SEER. From 2013 through 2015, ER-negative age-standardized incidence rates were 42.3 (95% CI, 38.7-46.3) per 100000 women for Ghanaian participants and 43.1 (95% CI, 42.0-44.3) per 100000 for US non-Hispanic Black women, both higher rates than that of 24.0 (95% CI, 23.6-24.4) per 100000 for US non-Hispanic White women. ER-positive age-standardized incidence rates were 42.1 (95% CI, 38.4-46.1) per 100000 women for Ghanaian participants, 105.4 (95% CI, 103.6-107.3) per 100000 for non-Hispanic Black women, and 128.5 (95% CI, 127.9-129.7) per 100000 for non-Hispanic White women. Conclusions and Relevance: In this cross-sectional study of Ghanaian and US non-Hispanic Black and non-Hispanic White women with breast cancer, age-standardized tumor incidence rates for women with ER-negative tumors in Ghana were similar to those for US non-Hispanic Black women, and both rates were higher than for US non-Hispanic White women. This finding may suggest increased susceptibility requiring elucidation in US non-Hispanic Black and West African populations.