Breast cancer in Black women is a killer. Data published by the Breast Cancer Research Foundation in 2016 reveals that, in the 50 most populous U.S. cities, Black women are 43 percent more likely to die of breast cancer than white women, and that disparity is widening. Breast cancer is the most commonly diagnosed cancer in black women, according to the American Cancer Society, and is their second-biggest cancer-related killer, following lung cancer. But at the same time, Black women have a lower incidence rate of breast cancer than white women. What's going on?

This new dose of science about Black women and breast cancer comes courtesy of the Carolina Breast Cancer at the University of North Carolina, which has been studying breast cancer in women since 1993 and studied more than 8,000 women with the illness around the state. They've been attempting to figure out why black women have higher mortality rates for breast cancer for decades, and this latest study may provide a clue.

The Carolina scientists looked at 980 breast tumors in women, and subjected them to two kinds of tests, which would determine which types and subtypes the tumors belonged to. They then looked at the races and ages of the women who had these tumors, and found some distressing results. Young Black women, according to the researcher's numbers, are much more likely to have triple-negative breast cancers, which don't respond to many of the treatments we conventionally use for breast cancer. The "triple negative" name means that they don't have the three most common things we know fuel breast cancer growth and target in treatment: estrogen, progesterone, or HER2 gene. The National Breast Cancer Foundation explains:

"Since the tumor cells lack the necessary receptors, common treatments like hormone therapy and drugs that target estrogen, progesterone, and HER-2 are ineffective. Using chemotherapy to treat triple negative breast cancer is still an effective option."

But why do young Black women have a higher rate of a cancer that's got fewer treatment options and a higher mortality rate? There's one genetic explanation. A lot of triple-negative tumors, according to studies, seem to come from a genetic flaw: a faulty BRCA1 gene. (That's the faulty gene that, paired with her family history of deadly breast cancer, prompted Angelina Jolie to undergo a double mastectomy.) And a study published in 2015 in the journal Cancer found that young Black women seem to have a high likelihood of having this faulty gene.

That's not all the Carolina scientists found, though. Black women in their study were much less likely than white women to have luminal A breast cancer, which is the easiest to treat. They were 50 percent more likely than white women to have HER2-enriched breast cancer, and 45 percent more likely to have luminal B. And in subtypes which were hormone-receptor positive and HER2-negative (which can fall under either luminal A or B), black women's tumors were more aggressive and more likely to recur after treatment.

The researchers are using these results to argue that the genomic testing of tumors should be standard to help give doctors the most information about possible breast cancer treatment; but it's also an alarming bit of news that adds into generations of data that black women are more likely to die of breast cancer. And genetics seems to be part of the reason why.

Figuring out why Black women die more of breast cancer goes beyond genetics, however. The Breast Cancer Research Foundation's 2016 data, which looked at cities and their particular health systems, found something interesting. "Differences in access to public health systems, and hence, differences in access to—and quality of—mammography and treatment are likely contributing to the problem," its author, Dr. Marc Hurlbert, wrote. That's supported by data coming out of the UK. In 2016, Cancer Research UK revealed that Black women in England are almost twice as likely to be diagnosed with advanced breast cancer as white women, and suggested that part of the problem was that Black women feel they have less access to mammograms and cancer screenings. "You'll get leaflets through your door and [the images] will be [of] predominantly of white, middle-class women. There's no representation of South Asian, African descent," a representative of the Black Health Initiative told the BBC.

Other answers are suggested, too. The Guardian reported in 2015 that experts were looking at the rising rates of mortality for breast cancer in Black women through the lens of childbearing choices, obesity, structural inequality, and environmental toxins — but also faced considerable internal disagreement about which of those aspects matter and which don't. Meanwhile, the disparity is likely going to continue to grow. The Center for Disease Control and Prevention notes that while breast cancer deaths themselves are going down, Black women's higher mortality rates don't appear to be shifting.

In light of the data about triple-negative breast cancer and the BRCA1 gene, one of the best ways to help black women seems to be finding a better treatment for the most aggressive types of breast cancer — and fast. A complicated therapy involving a medication known as a PARP inhibitor for triple-negative and basal cell breast cancers may show promise in the future, but isn't widely in use at the moment. Hopefully, though, with more scientists diving into the fray every year, this aspect of the disparity, at least, may one day have a better outcome.