Gene variants and breast cancer risk in Black women

Breast cancer is the most often diagnosed cancer in many parts of the world, including the U.S. More than 310,000 new cases are expected nationwide this year.

Black women tend to develop breast cancer at a younger age than White women. Black women are also more likely than Whites to die from the disease, and they are twice as likely to develop an aggressive subtype called triple-negative breast cancer. But despite the increased risks faced by women of African descent, most large-scale genetic studies of breast cancer to date have focused on women of European ancestry.

To better understand their unique genetic risks, a research team led by Dr. Wei Zheng of Vanderbilt University analyzed genetic data from over 40,000 females of African descent. About 18,000 had been diagnosed with breast cancer. The data were gathered as part of the NIH-funded African Ancestry Breast Cancer Genetic consortium, which combined data from 26 studies. Most participants (85%) were African Americans. The rest were from Barbados or Africa.

The researchers conducted a genome-wide association study (GWAS) to look for genetic variants that are found more often in participants with breast cancer than in those without. This is believed to be the largest GWAS study to date of breast cancer in this population. Results were reported in Nature Genetics on May 13, 2024.

The analysis pinpointed 12 genetic regions, or loci, associated with breast cancer. Three of these loci were linked to the aggressive triple-negative cancer. About 8% of the women carried two genetic copies of risk variants in all three of these loci. Such women, the researchers found, were 4.2 times more likely to be diagnosed with triple-negative breast cancer than women who had only one or no copies of the variants.

Because this type of cancer lacks specific cell receptors often seen with breast cancer (like estrogen or HER2 receptors), there are fewer targeted options for treatment. These findings may help researchers identify new treatment targets.

The researchers also confirmed many breast cancer risk variants that were found earlier in other populations. And they identified an uncommon risk variant in the gene ARHGEF38, which had been previously linked to aggressive prostate and lung cancers.

The scientists used their findings to create polygenic risk scores (PRS) for breast cancer risk in females of African descent. PRS use genomic data to gauge the chance that a person will develop a certain medical condition. PRS created previously, using results from other populations, tend to perform poorly at predicting breast cancer risk for Black women. The new PRS, based on genomic data from African descendants, outperformed previous PRS at predicting breast cancer risk in this population.

BC4

The findings and data could lead to improved detection of breast cancer in this at-risk population and provide clues for potential treatment targets. Studies with even larger, more diverse populations will be needed to further improve the prediction of breast cancer risk.

“We have worked with researchers from more than 15 institutions in the U.S. and Africa to establish this large genetic consortium,” Zheng says. “Data put together in this consortium have been and will continue to be used by researchers around the world.”

—by Vicki Contie

See the facts

What Black women need to know about breast cancer

By Jessica Saenz

Thanks to improved therapies and early detection, breast cancer is increasingly treatable. Despite these improvements, breast cancer is now the leading cause of cancer death among Black women, according to a new report by the American Cancer Society.

Black women are now 41% more likely to die from breast cancer than white women, despite a lower risk of being diagnosed with the disease. This is partly because Black women are more likely to be diagnosed with breast cancer at a later stage when it is harder to treat.

But Black women have lower survival rates for every stage of breast cancer diagnosis. Many complex factors contribute to this gap in care outcomes ― all of which are fueled by systemic racism that limits access to high-quality cancer treatment.

As health care professionals work to address the disparities in cancer care for Black women and other minorities, increasing awareness of these disparities is imperative. If you are a Black woman, this is what you need to know about breast cancer:

Breast cancer screening is the best defense against breast cancer.

When life gets busy, it's easy to delay or even skip important health screenings. But the longer cancer goes undetected, the more opportunity it has to grow and spread. Regular screenings are the best way to detect cancer early, when it is easier to treat.

"We know that African American women are less frequently undergoing screening mammography. If that were fixed, it would go a long way toward overcoming this disparity," says Donald Northfelt, M.D., a Mayo Clinic hematologist and oncologist, and breast cancer researcher. "To have a diagnosis of breast cancer made earlier through screening, when the tumors are smaller and can be more easily removed, would be a big advance."

"I'm the first to admit that sometimes the information out there is confusing because there are different guidelines. Mayo Clinic and the American Cancer Society recommend that you start your screening mammograms at the age of 40 and continue to do them annually," says Michele Halyard, M.D., a Mayo Clinic radiation oncologist and co-founder of the Coalition of Blacks Against Breast Cancer.

The best approach for wading through competing information is to talk to your health care professional. Together, you can identify risk factors and preferences that might change how often you should be screened.

"Talk to your health care provider about what is best for you," says Dr. Halyard. "Don't be afraid of mammograms. There might be a bit of discomfort, but it is well worth it to save your life, and early detection is the key."

Genetic testing can expose your inherited risk factors.

When you discuss screening recommendations with your health care professional, it helps to give them a full picture of your risk factors, including lifestyle choices and medical history. But knowledge of the risk factors in your genes is just as important, and the best way to reveal these mutations is through genetic testing.

"A woman who has an identified genetic predisposition to cancer needs to be screened more frequently. That's how we can detect the cancer early and help her more effectively," says Dr. Northfelt. "Get your genetic testing done. If you have a genetic predisposition, then we want you to be screened every six months."

Talk to your health care professional about genetic testing, how you can obtain it and if it's right for you. If you decide you prefer an over-the-counter genetic test, know that the data these tests provide can be insightful. But it's important to review results with a genetic counselor or your health care professional to understand how they affect your risk of breast cancer or other diseases.

While a family history of breast cancer is concerning and should be discussed with your health care professional, most breast cancers are not linked to family genetics, says Dr. Halyard. "Only about 5% to 10% of breast cancers have a genetic link. That includes BRCA1, BRCA2 and some other genes that are associated with breast cancer. That may change as we get more information in the future, but that's what we know today."

Black women are more likely to have an aggressive form of breast cancer.

"Black women are at higher risk for triple-negative breast cancer, which is the most aggressive type of breast cancer. And it tends to occur at younger ages," says Dr. Halyard.

Triple-negative breast cancer, also called basal-like breast cancer, is not sensitive to the hormones estrogen or progesterone and does not produce too much of the growth-promoting protein called HER2. This makes it difficult to treat.

Triple-negative breast cancer accounts for 35% of breast cancer diagnoses in African Americans, and it is associated with a high rate of recurrence and poor five-year survival rates, according to a study led by Fergus Couch, Ph.D., a geneticist at Mayo Clinic.

Triple-negative breast cancer is traditionally treated with chemotherapy and, though more research is needed, immunotherapy has shown some promise.

If you have dense breasts, you might need additional screening tests.

About half of women undergoing mammograms have dense breast tissue. Though it's common and normal, many women with dense breast tissue are unaware of it. A radiologist who analyzes your mammogram can determine the level of density on your breast.

"Breast density is a problem because on a mammogram, dense breast tissue looks white or gray, and cancers also look white or gray. It's possible for breast density to hide cancer in the breast," says Dr. Northfelt. "There are various techniques that we can use to overcome that. We have contrast-enhanced mammography, MRIs and ultrasound exams that can help overcome the problem that breast density creates and allow us to see the breast tissue more clearly."

Women who are younger, have less body fat or take hormone therapy for menopause are more likely to have dense breast tissue, but the only way to know with certainty is to talk to your health care professional and determine the best screening test for you.

"It's important for women to understand their breast density and seek better answers if they're told they have dense breasts without further explanation. That's not satisfactory," says Dr. Northfelt.

Second opinions are important and should be encouraged.

Understand that you have the right to ask questions and get further clarification. If you are unsatisfied or your instincts tell you otherwise, ask for a second opinion.

"If we were shopping online for shoes, we would check a number of sites," says Pamela McCall, a radiology systems analyst at Mayo Clinic and an 18-year breast cancer survivor. "If they don't have the right color, we're not buying. We would look until we found the shoes to match the dress or the purse. It's worth taking that time for yourself. As women, we tend to be caregivers, but it's worth taking this time for your health."

Still, some people might not feel comfortable asking for a second opinion or raising concerns about their care to their health care professional. If this is the case for you, preparing ahead of time or bringing a family member can help.

"Sometimes people are overwhelmed when they're diagnosed, and they don't get their questions answered, or they're too timid to ask questions. Keep persisting and understand the information about your breast cancer," says Dr. Halyard. "If you're a family member, be that voice of support. Go with them to appointments and ask questions for them if they are not comfortable."

You can also seek a second opinion without a referral from your current health care professional. This will require some work on your end, but the peace of mind can make it worth the effort.

"There's been a tragic lag in the improvement in breast cancer outcomes for African American women. Currently, 90% of women in the U.S. survive five years after a breast cancer diagnosis, which means we don't typically expect the cancer to come back," says Dr. Northfelt. "In African American women, that number is only about 83% to 84%."

With more research uncovering inequities and their solutions, cancer experts at Mayo Clinic and around the world are working toward improved outcomes for Black women and other minorities.

"There are many things we need to work on and correct to overcome this disparity and bring African American patients to the same level of success that everyone else is achieving, and we're working on that diligently at Mayo Clinic," says Dr. Northfelt. "We need to make sure that African American women have access to better care to overcome this disparity and have just as good an outcome as everybody else in our country."

Breast Cancer Death Rates Are Highest for Black Women—Again

Cancer mortality rate

These findings are published in “Breast Cancer Statistics, 2022” in CA: A Cancer Journal for Clinicians, led by ACS cancer surveillance researcher Angela Giaquinto, MSPH. Giaquinto and Rebecca Siegel, MPH, as well as their department lead Ahmedin Jemal, DVM, PhD, also produced the consumer-friendly companion, Breast Cancer Facts & Figures 2022-2024. These reports provide detailed analyses of breast cancer occurrence and current information on known risk factors, early detection, and treatment.

Here's an overview of some key statistics from both reports.

New diagnoses of breast cancer continue slow increase in 2022.

Breast cancer is the most commonly diagnosed cancer among women in the US, after nonmelanoma skin cancer. It mostly affects women age 50 and older, who develop about 83% of new breast cancer cases and represent 91% of deaths from breast cancer. Half of the women who die from breast cancer in the US are age 70 or older.

Men can get breast cancer, too, but this is much less common. In 2022, an estimated 287,850 women and 2,710 men will be diagnosed with breast cancer. An estimated 43,250 women and 530 men will die from the disease.

Breast cancer incidence rates have risen slowly in most of the past 40 years. During the most decade of data, 2010 through 2019, the rate increased by 0.5% a year. The increase is likely due at least in part to more women having excess body weight and the declining fertility rate of women in the US.

The total fertility rate of a population is the average number of children born to a woman over her lifetime, and it’s been found to be related to the risk of developing breast cancer. Women who have not given birth to children or who gave birth to their first child after age 30 have a slightly higher overall risk for developing breast cancer later in life. Having many pregnancies and becoming pregnant before age 30 reduces a woman’s risk of developing breast cancer.

The effect of weight and fertility rates seem to be limited to an increased risk of hormone receptor-positive breast cancer (HR+)—the most common type of breast cancer and the largest driver of increasing incidence rates. HR+ tumors are more likely to be detected early through mammography compared to HR- tumors, and they have higher survival.

Most new breast cancer cases are diagnosed at a localized stage, meaning they have not spread outside of the breast. These early-stage cancers are most often found during breast cancer screening and typically have a high rate of survival because treatment is more effective at this stage.

Black women still have a 4% lower incidence rate of breast cancer than White women but a 40% higher breast cancer death rate.

Cancer stats in black women

In this graphic, the breast cancer incidence rate (light pink bars) is highest in White women and lowest in Hispanic women. The breast cancer death-rate (dark pink bars) is highest in Black women, followed by American Indian/Alaska Native (AIAN) women, and lowest in Asian/Pacific Islander women. It's notable that Black and AIAN women both have a higher death rate than White women even though they both have a lower incidence rate for breast cancer than White women.

Breast cancer is the second leading cause of cancer death after lung cancer in women in the US overall, but it’s the leading cause of cancer death in Black and Hispanic women.

During 2016 through 2020, the breast cancer incidence rate was higher in Black women compared to White women in only 4 states: Alabama, Louisiana, Mississippi, and Virginia. In contrast, the breast cancer death rate was higher for Black women than White women in every state except Washington.

“Geographical disparities in breast cancer incidence and mortality are due to the differences in the prevalence of risk factors and access to screening and treatment. All of these are influenced by a woman’s socioeconomic status and her distance to medical services, as well as government policies in the state where she lives, such as whether it expanded Medicaid.”

Rebecca Siegel, MPH

Overall, the pace of the reduction in female breast cancer death rates is slower than it was during the 1990s and 2000s. Still, the 43% overall decline in mortality translates to 460,000 deaths avoided between 1989 and 2020. This decline is attributed to earlier detection through breast cancer screening and increased awareness of the disease as well as improvements in treatment.

The racial disparity in deaths from breast cancer has remained at 40% or higher for a decade.

  • Black women younger than age 50 had a death rate that was twice as high as White women that age. Plus, Black women are more likely than White women to die of breast cancer at any age.
  • AIAN women were 17% less likely to be diagnosed with breast cancer than White women but 4% more likely to die from the disease.
Cancer incidents

Part of the reason the breast cancer death rate is not dropping as fast as it has in previous years is because screening rates aren’t increasing and too few women are receiving timely and high-quality treatment after they’re diagnosed with breast cancer.

The study authors point out that “progress against breast cancer mortality could be accelerated by mitigating racial disparities through increased access to high-quality screening and treatment via nationwide Medicaid expansion and partnerships between community stakeholders, advocacy organizations, and health systems.”

“Coordinated and concerted efforts by policy makers, healthcare systems, and providers are needed to provide optimal breast cancer care to all populations and reduce breast health disparity and accelerate progress against the disease. These efforts include expansion of Medicaid in the 12 non-expansion states and increased investment for new early detection methods and treatments.”

Ahmedin Jemal, DVM, PhD, ACS senior vice president of Surveillance & Health Equity Science

Black women have the lowest survival for all subtypes of breast cancer.

Cancer stats in black women

In this graphic, the bars show the percentage of women who are still alive 5 years after a cancer diagnosis based on the cancer’s stage when they were diagnosed (listed along the bottom) and their ethnicity (shown by color). At each stage, Black women, who are represented by the light pink bars, have the lowest survival. Black women who develop breast cancer are less likely than any other race to be alive 5 years after their diagnosis, regardless of when their cancer’s when discovered or what type it is.

On January 1, 2022, more than 4 million women were living in the US with a history of invasive breast cancer. Some of them were cancer-free, while others still had evidence of cancer and may have been undergoing treatment.

  • Black women have the lowest 5-year relative breast cancer survival rate compared to all other racial/ethnic groups for every stage of diagnosis and every breast cancer subtype.
  • The largest disparities in 5-year relative survival are for regional and distant stage breast cancer. Only 78% of Black women are living at least 5 years after their diagnosis of regional stage breast cancer compared to 88% of White women. For distant stage, the gap is slightly larger – 21% versus 32%
  • There is a 6% to 8% gap in 5-year survival between Black and White women for every breast cancer subtype.

Up to about 30% of breast cancers may be preventable with changes in lifestyle.

1 in 8 women

About 30% of breast cancer diagnoses are linked to risk factors that women may be able to change—such as excess body weight, physical inactivity, and alcohol intake.

Women can help lower their risk for developing breast cancer by being active, maintaining a healthy body weight, and limiting alcohol. They can also help lower their risk of death from breast cancer by talking with their doctor about how often to get a mammogram, sticking with that schedule, and promptly following up on any abnormal results. Following American Cancer Society guidelines for breast cancer screening can help women find breast cancer earlier, when treatments are more likely to be effective.

The advocate affiliate of the ACS, the American Cancer Society Cancer Action Network (ACS CAN) continues to make efforts to close this persistent gap in screening.

“Lawmakers can and must do more to address the unequal burden of breast cancer among Black women, including increasing funding for the National Breast and Cervical Cancer Early Detection Program (NBCCEDP), a program jointly funded by federal and state governments that helps improve access to lifesaving screenings for these cancers.”

Lisa A. Lacasse, ACS CAN president
Cancer map

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