Understanding Hereditary Breast Cancer: 72 Genetic Mutations and Risk

According to the National Cancer Institute, invasive breast cancer affects approximately one in eight U.S. women, and about 5 percent to 10 percent of all breast cancers are hereditary.

At present, most people are familiar with BRCA1 and BRCA2 gene mutations, which are inherited gene mutations—or abnormalities in the DNA sequencing—that increase the risk of developing breast cancer.

According to statistics from the National Cancer Institute, by age 80, about 72% of women who’ve inherited a BRCA1 gene mutation and approximately 69% of women who’ve inherited a BRCA2 gene mutation will likely be diagnosed with breast cancer.

But this data only accounts for a small portion of women who will develop the disease. Are scientists any closer to determining additional genetic variants or factors that may play a role in the development of breast cancer? Actually, they are.

Two Studies Shed Light on New Gene Mutations

In October 2017, two studies were published in the journals Nature and Nature Genetics, respectively, which reported on the findings of 72 previously undiscovered gene mutations that increase a woman's risk of developing breast cancer. The international team, which conducted the studies, is called the OncoArray Consortium, and it brought together more than 500 researchers from over 300 institutions around the world—this study is being hailed as the most extensive breast cancer study in history.

To gather the information for this study, researchers analyzed the genetic data of 275,000 women—146,000 of whom had received a diagnosis of breast cancer. This vast collection of information is helping scientists identify new risk factors that predispose some women to breast cancer and may provide insights as to why certain types of cancers are more difficult to treat than others. Here are some of the specifics regarding this groundbreaking research:

• In two studies, researchers discovered a total of 72 new gene mutations that contribute to hereditary breast cancer.
• To locate these genetic variants, researchers analyzed the DNA of blood samples from women involved in the study; nearly half had received a breast cancer diagnosis. The DNA was measured at more than 10 million sites across the genome in search of subtle clues as to whether the DNA in women who had been diagnosed with breast cancer was somehow different from the DNA in those who hadn’t been diagnosed.
• Of the 72 variants the researchers located, 65 of them were broadly associated with an increased risk of developing breast cancer.
• The remaining seven variants correlated with an elevated risk of developing hormone-receptor-negative breast cancer. The American Cancer Society defines this type of breast cancer by stating, “Hormone receptor-negative (or hormone-negative) breast cancers have neither estrogen nor progesterone receptors. Treatment with hormone therapy drugs is not helpful for these cancers.” In other words, these genetic variants may cause a type of breast cancer in which hormone drugs and treatments, like Tamoxifen or Femara, won’t be sufficient.
• When added to previous discoveries, these new findings bring the total count of genetic mutations associated with an increased risk of developing breast cancer to around 180.
• As stated in the study, the newly discovered genetic variants increase a woman's risk of developing breast cancer by roughly 5 percent to 10 percent. While these mutations aren’t as influential as BRCA1 and BRCA2, the research suggests these small variants may have a compounding effect on the women who have them, which could increase the potential to develop the disease.

What This Means for Women at Risk of Developing Hereditary Breast Cancer

Breastcancer.org, a non-profit organization committed to the mission of gathering information and creating a community for those affected by breast cancer, shares this information, “Most people who develop breast cancer have no family history of the disease. However, when a strong family history of breast and/or ovarian cancer is present, there may be reason to believe that a person has inherited an abnormal gene linked to higher breast cancer risk. Some people choose to undergo genetic testing to find out. A genetic test involves giving a blood or saliva sample that can be analyzed to pick up any abnormalities in these genes.”

Currently, the most common genetic tests for this disease are the BRCA1 and BRCA2 gene mutations. But as science introduces additional genetic variants linked to breast cancer, your healthcare provider may recommend further testing with a genetic counselor. If your personal or familial history suggests you could be a carrier of other genetic abnormalities, a more elaborate genetic panel may be of benefit to you. As advancements in the field of genetics continue, more accurate testing procedures will allow for earlier detection of breast cancer risk factors, a more individualized approach to care, and better treatment options.

Are There Preventative Measures Women Can Take?

Breastcancer.org recommends that women who are aware they have a genetic mutation linked to breast cancer consider implementing the following preventive measures to lessen the risk:

• Keep weight in a healthy range
• Engage in a regular exercise program
• Avoid smoking
• Consider reducing or eliminating alcohol
• Eat a nutrient-rich diet

More aggressive preventative strategies may include:

• Begin screening for hereditary breast cancer at an earlier age, depending on a woman's family history
• Hormonal therapies
• A prophylactic mastectomy, or surgical removal of the healthy breasts​​​

A Word From Verywell

Each woman’s family history is unique, so there’s no one-size-fits-all approach to preventing or treating hereditary breast cancer. If you’re at risk of developing hereditary breast cancer, be proactive and talk with your healthcare provider about how to best reduce your risk of the disease and, if necessary, the appropriate medical interventions available to you.

Should you find yourself facing the scary diagnosis of breast cancer, reach out to others for support. The breast cancer community is thriving, and it’s filled with some of the most resilient women you’ll ever meet. They'll encourage you on your journey. Plus, having the extra support can ease the feelings of isolation that may come about with a breast cancer diagnosis.