Survival rates for patients with breast cancer are improving, but black women remain more likely to die from the disease than white women. To figure out why, the National Institutes of Health (NIH) announced Wednesday that it would be launching the largest-ever study of breast cancer genetics in black women. The National Cancer Institute’s (NCI) Division of Cancer Control and Population Sciences (DCCPS) is administering the $12 million grant that will fund the study.

“This effort is about making sure that all Americans— no matter their background— reap the same benefits from the promising advances of precision medicine,” Dr. Douglas R. Lowy, acting director of the National Cancer Institute, under the NIH, said in a news release. “I’m hopeful about where this new research can take us, not only in addressing the unique breast cancer profiles of African-American women, but also in learning more about the origin of cancer disparities.”

Data show black women are more likely than white women to be diagnosed with aggressive subtypes of breast cancer. For example, the rate of triple-negative breast cancer, one such subtype, is twice as high in black women compared with white women.

While studies suggest genetic, environmental and societal factors like access to health care may all play a role, the exact reason why mortality rates for black women with breast cancer remains unknown.

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For the study, researchers will compare the genomes of 20,000 black women with breast cancer with those of 20,000 black women without the disease. Researchers will compare the genomes with those of white women with breast cancer as well. Next, they will look for inherited genetic variations linked with breast cancer risk in black women compared to white women, and they will investigate gene expression in breast cancer tumor samples to identify how tumors develop genetically.

“A better understanding of the genetic contributions to differences in breast cancer diagnoses and outcomes among African-Americans may lead to better treatments and better approaches to cancer prevention,” Robert Croyle, Ph.D., director of the DCCPS, said in the news release.

In October 2015, the American Cancer Society released findings that suggested incidence of breast cancer among black women had reached that of white women— a troubling finding given their already-higher risk of death from the disease.

The study found that as of January 2014, more than 3.1 million women living in the United States had a history of breast cancer, but, thanks to advances in medicine, death rates from the disease have dropped 36 percent since 1989. Historically, black women have had a lower incidence rates than white women, but by 2012, death rates for the disease were 42 percent higher in black women than white women. Study authors wrote that they expected the trend to persist.