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 18 321 non-Hispanic Black women (age range, 20-74 years; 5117 [29%] ER-negative) and 103 227 non-Hispanic White women (age range, 20-74 years; 15 040 [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 100 000 women for Ghanaian participants and 43.1 (95% CI, 42.0-44.3) per 100 000 for US non-Hispanic Black women, both higher rates than that of 24.0 (95% CI, 23.6-24.4) per 100 000 for US non-Hispanic White women. ER-positive age-standardized incidence rates were 42.1 (95% CI, 38.4-46.1) per 100 000 women for Ghanaian participants, 105.4 (95% CI, 103.6-107.3) per 100 000 for non-Hispanic Black women, and 128.5 (95% CI, 127.9-129.7) per 100 000 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.