Black women and white women diagnosed with breast cancer have about the same rates of genetic mutations linked to a higher risk of breast cancer, according to a study.
The research was published online on May 27, 2021, by the journal JAMA Oncology. Read the abstract of “Comparison of the Prevalence of Pathogenic Variants in Cancer Susceptibility Genes in Black Women and Non-Hispanic White Women With Breast Cancer in the United States.”
A germline variant is a change, or mutation, in a gene that you inherit from your parents and is in all your DNA. “Pathogenic” means the mutation is harmful and usually linked to a disease — in many cases, cancer.
Genetic mutations linked to breast cancer
Two of the most well-known genes that can mutate and raise the risk of breast and/or ovarian cancer are BRCA1 and BRCA2. Women who inherit a mutation in either of these genes — from their mothers or fathers — have a much higher-than-average risk of developing breast cancer and/or ovarian cancer.
The average woman’s risk of developing breast cancer in her lifetime is about 13%. According to the National Cancer Institute (NCI), women with a BRCA1 mutation have between a 55% and 72% lifetime risk of developing breast cancer, while women with a BRCA2 mutation have between a 45% and 69% lifetime risk of developing breast cancer.
Men with these mutations — particularly a BRCA2 mutation — also have an increased risk of breast cancer and possibly an increased risk of prostate cancer.
About 5% to 10% of breast cancers are thought to be hereditary, meaning the cancer is linked to mutations in genes passed from parent to child.
You are substantially more likely to have a genetic mutation linked to breast cancer if:
- you have blood relatives (grandmothers, mother, sisters, aunts) on either your mother’s or father’s side of the family who were diagnosed with breast cancer before age 50
- there is both breast and ovarian cancer on the same side of the family or in a single individual
- you have a relative with triple-negative breast cancer
- there are other cancers in your family in addition to breast, such as prostate, melanoma, pancreatic, stomach, uterine, thyroid, colon, and/or sarcoma
- women in your family have had cancer in both breasts
- you are of Ashkenazi Jewish (Eastern European) heritage
- you are a Black woman and have been diagnosed with breast cancer at age 35 or younger
- a man in your family has had breast cancer
- there is a known breast cancer gene mutation in your family
Breast cancer in Black women
Although the lifetime risk of breast cancer is similar for Black women and white women, Black women are more likely to be diagnosed when they are younger and with more aggressive breast cancers, such as triple-negative.
Triple-negative breast cancer is:
So neither the hormones estrogen and progesterone nor the presence of too many HER2 receptors drive triple-negative disease growth. This means that triple-negative breast cancer doesn’t respond to hormonal therapy or therapies that target HER2 receptors.
Triple-negative breast cancer makes up about 10% to 12% of all breast cancers — more than one out of every 10 — and tends to be more aggressive than other breast cancers.
Black women also are more like to die from breast cancer than white women.
About the study
The researchers in this study wanted to see why Black women are diagnosed with aggressive breast cancers and at younger ages. The researchers thought the reason could be related to differences in genetic mutations between Black women and white women.
To explore their theory, the researchers looked to see if the rates of genetic mutations linked to breast cancer were higher in Black women diagnosed with breast cancer than white women diagnosed with breast cancer.
The study used information from the CARRIERS (Cancer Risk Estimates Related to Susceptibility Genes) consortium, a group of 17 large studies in the United States focused on women in the general population who develop breast cancer. The CARRIERS consortium involves more than 30,000 women diagnosed with breast cancer and more than 30,000 similar women who have had genetic testing for mutations linked to a higher risk of breast cancer.
For this analysis, the researchers looked at information from:
- 3,946 Black women who were diagnosed with breast cancer
- 25,287 white women who were diagnosed with breast cancer
The researchers found that, compared with white women, Black women were:
- more likely to be diagnosed at a younger age
- more likely to be diagnosed with triple-negative breast cancer
- more likely to be diagnosed with estrogen-receptor-negative breast cancer
- less likely to have a first-degree relative (sibling or parent) diagnosed with breast cancer
- more likely to have a family history of ovarian cancer
The rates of genetic mutations among the two groups of women were similar. The study showed:
- 223 (5.65%) Black women had a mutation in one of the 12 genes confirmed to have a link to breast cancer
- 1,279 (5.06%) white women had a mutation in one of the 12 genes confirmed to have a link to breast cancer
Still, the researchers found the following differences in the actual genetic mutations:
- white women diagnosed with breast cancer were more likely to have a CHEK2 mutation than Black women
- Black women diagnosed with breast cancer were more likely to have mutations in the BRCA2 and PALB2 genes than white women
The researchers also looked to see if the rates of genetic mutations varied based on the cancer’s estrogen receptor status.
Among women diagnosed with estrogen-receptor-positive breast cancer:
- Black women were more likely than white women to have a BRCA2 mutation
- white women were more likely than Black women to have a CHEK2 mutation
Still, the rate of overall rates of genetic mutations linked to breast cancer was 4.38% for both groups of women.
Among women diagnosed with estrogen-receptor-negative breast cancer:
- Black women were more likely than white women to have a PALB2 mutation
Again, the overall rate of genetic mutations was similar for both groups of women: 9.28% for Black women and 8.08% for white women.
The researchers noted that more than 75% of the genetic mutations seen in estrogen-receptor-negative breast cancer were in the BRCA1, BRCA2, or PALB2 genes.
There were no differences in rates of genetic mutations between the two groups of women when the researchers looked at women diagnosed before age 50.
“In this study among Black and non-Hispanic white women with breast cancer in the US, we found no difference in the prevalence of [pathogenic variants] in 12 breast cancer susceptibility genes,” the researchers concluded. “The present study findings, from, to our knowledge, the largest population-based sample of Black patients along with non-Hispanic White patients from similar or the same studies, suggest that there is not sufficient evidence to make changes to genetic testing guidelines based on race alone. All efforts should be made to ensure equal access to and uptake of genetic testing to minimize disparities in care and outcomes.”
What this means for you
If you’re a Black woman who had been diagnosed with breast cancer, this study offers some reassuring, yet frustrating news.
Black women don’t have higher rates of genetic mutations than white women, which is good news. But it doesn’t help us understand why Black women are more likely to be diagnosed at a younger age and with more aggressive types of breast cancer.
If you’ve been diagnosed with breast cancer, consider talking to your doctor or a licensed certified genetic counselor about your diagnosis and your family history and asking if genetic testing makes sense for you. Either your doctor or a licensed certified genetic counselor can help you understand the test and accurately interpret the results.
Learn more about genetic testing, including different types of genetic tests and how results are reported.
Read about breast cancer risk factors for more information on genes and genetic mutations linked to breast cancer, as well as all the risk-lowering steps you can take if you have a genetic mutation.
If you’ve tested positive for a mutation linked to breast cancer and would like to talk with others who have also tested positive, join the Breastcancer.org Community's Genetic Testing forum.
Written by: Jamie DePolo, senior editor
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