We’ve known for a while that triple-negative breast cancer is more common in Black women in the United States, compared to other groups. The news is the prevalence varies significantly depending on where these women were born. American Cancer Society (ACS) researchers found that among Black women, those born in the US and Western Africa were diagnosed more often with triple-negative breast cancer than women born in East Africa. The authors published their findings in Cancer, an ACS peer-reviewed journal.
Previous studies have reported that Black women in the US are twice as likely as white women to be diagnosed with triple-negative breast cancer. This study, however, suggests that saying that all Black women have a higher risk of being diagnosed with this cancer type may be too general of a statement.
Using the National Program of Cancer Registries, the ACS researchers identified 65,211 non-Hispanic Black women who were diagnosed with invasive breast cancer from 2010 to 2015. The women were recorded as being born in the US, East Africa, West Africa, or the Caribbean.
Compared with the prevalence of triple-negative breast cancer among Black women born in the US, Black women born in:
There wasn’t enough data to analyze the prevalence rates of Black women born in North, Central, or South Africa. This is one of the few studies to examine how place of birth relates to Black women’s risk of breast cancer.
Triple-negative breast cancer tends to grow and spread faster than most types of breast cancer. These cancer cells don’t have estrogen, progesterone, or human epidermal growth factor (HER2) receptors (proteins). The lack of these receptors means that some common treatments, like hormone therapy or targeted therapy, don’t work for this type of breast cancer.
It’s not clear what risk factors for developing breast cancer may be associated with birthplace. The differences could be due to genetics. Most Black women born in the US or in the Caribbean are likely descendants of people who were involuntarily migrated from West Africa to North America during the 16h to 18th centuries, often through the Caribbean. Ancestry studies among Black people living in Chicago, Baltimore, Pittsburgh, and North Carolina reflect the historic migration. Ancestry in those places is 71% Western Africa. The differences could also be due to risks from values, traditions, social structures, income, or health behaviors, such as eating a western diet.
“Our results tell us that knowledge based on such a broad categorization of Black versus white women may mask the complexity of the differences in breast cancer that appeared to be present within Black women,” says Hyuna Sung, PhD, a principal scientist in surveillance research at the ACS and lead author on this study.
The main limitation of the study was missing information about birthplace. The researchers say it’s important to take birthplace into consideration when studying different types of breast cancer in women of African descent in the US and other parts of the world. This could help cancer experts better understand the diversity of breast cancer among Black women. The authors say their study “calls for a concerted effort for more complete collection of birthplace information in cancer registries.”