Triple-negative breast cancer is notoriously hard to treat and tends to be more aggressive. It’s also more common among Black women. A new study has found just how much higher the risk is for this group.

Researchers from the University of Pennsylvania looked at the mammogram histories of just under 200,000 patients, including about 30,000 Black women. In this analysis, they found that Black women had nearly three times the risk of developing triple-negative breast cancer.


Dr. Anne Marie McCarthy, study team member and assistant professor of epidemiology at the University of Pennsylvania, says, “In our studies, we see clear differences in risk factors across these types of breast cancers, and we need to do a better job of identifying how we can accurately predict risk for women, particularly for women of color.”

The study examined data from 198,278 women who had received mammograms between 2006 and 2015 at three different U.S. health systems. Among these women, 4,002 invasive cancers were diagnosed, including 300 cases of triple-negative breast cancer. From these figures, researchers saw that Black women had 2.7 times the risk of developing TNBC than white women.

The study says, “While it is well known that Black women have higher risk of TNBC, it is striking that Black women had nearly threefold increased risk even with comprehensive adjustment for breast cancer risk factors in a screened population.”


This diagnosis was found to be problematic in other ways, including that TNBC was less apt to be detected during screening and more apt to be diagnosed within 12 months of a normal mammogram.

Age, BMI, and breast density were also risk factors related to a TNBC diagnosis.

Regarding age, researchers said, “We observed that older age was associated with an increased risk of TNBC. This may seem to be inconsistent with the prior literature reporting younger age to be associated with increased risk of TNBC.”

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They explained that this is because they were comparing women diagnosed with TNBC to women who had not been diagnosed with cancer, while other studies compare the prevalence of TNBC with other types of breast cancer in certain age groups.

They said, “While patients with TNBC may be younger than patients diagnosed with other tumor subtypes, TNBC incidence increases with age. Based on SEER estimates, the TNBC incidence rate is 4.0 per 100,000 for women aged 20–39 years compared with 38.9 per 100,000 for women aged 65 and older.”


The team hopes that a large takeaway from their study is the need to explore genetic, environmental, or biomarker factors that may lead to such a higher incidence of TNBC in Black women. You can read the full study in the journal Cancer Medicine.

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