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For Black women with HR–positive/ERBB2–negative breast cancer, a higher percentage of West African ancestry is associated with shorter disease-free survival.

Having a higher percentage of West African genetic ancestry is associated with shorter disease-free survival among Black women with hormone receptor (HR)–positive/human epidermal growth factor receptor 2 (ERBB2 [formerly HER2])–negative breast cancer, according to findings published in JAMA Network Open.

“Consequently, our study highlights the importance of genetic ancestry–based analyses beyond self-reported race,” Sonya Reid, MD, and colleagues wrote.

The study investigated associations of biological and non-biological factors with disease-free survival in young Black women with breast cancer, a population with reduced breast cancer survival compared with White women. The analysis included 687 Black women diagnosed with invasive breast cancer at age 50 years or younger from 2005 to 2016 from cancer registries in Florida and Tennessee. Models were adjusted for immunohistochemistry subtype, lymph node (LN) status, and full-time employment.

The median age at early-stage invasive breast cancer diagnosis was 44 years, according to the study results. Median follow-up was 10 years.

Disease-Specific Outcomes Tied to Genetic Ancestry

Most women in the study (n=551) had their global genetic ancestry identified through DNA analysis of saliva samples. Compared with all patients with global ancestry data, the 246 patients in the HR-positive/ERBB2-negative subgroup showed an association between shorter disease-free survival and a higher percentage of West African genetic ancestry, with researchers reporting a hazard ratio of 1.45.

Tumor gene expression assays identified an overrepresentation of aggressive non–luminal A subtypes, the researchers reported, which were the most common tumors in women with HR-positive/ERBB2-negative breast cancer.

Additional Impact of Cancer Type on Socioeconomics

Triple-negative breast cancer (TNBC) and LN involvement were associated with shorter breast cancer disease-free survival in multivariable analysis, according to the study results. Hazard ratios of shortened disease-free survival were 1.81 with TNBC and 1.77 with LN involvement.

Conversely, full-time employment was linked with improved outcomes, with a hazard ratio of 0.44 for shortened disease-free survival.

“The association we observed with employment may be related to several potential etiologies, such as benefiting from the socioeconomic advantages working may have afforded or feeling well enough to keep working after a cancer diagnosis,” Dr. Reid and colleagues wrote.

“Moving forward, it is critical to include genetic ancestry and gene expression assays to both expand our knowledge and improve clinical tools, such as prognostic and predictive assays, to address the disproportionate mortality burden faced by young Black women with breast cancer,” the researchers added.