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Home > Understanding Breast Cancer > Risk Factors and Prevention > Family History & Genetic Risks > Inherited Gene Mutations

  


Inherited Gene Mutations

 

 

Questions to ask your doctor about genes and inherited breast cancer
Topic Card

 

Genetics and Breast Cancer
Fact Sheet

  

Research Fast Facts: BRCA1 & BRCA2  
Fact Sheet

Some inherited gene mutations have been linked to breast cancer. These include mutations in the following genes:

  • BRCA1  
  • BRCA2  
  • p53  
  • CHEK2  
  • ATM  

Other genes are under study and may also play a role in breast cancer.  

Inherited mutations known to increase the risk of breast cancer are rare in the general population. These mutations account for only five to 10 percent of all breast cancers diagnosed in the U.S. [4,26]. 

 Komen Perspectives 

 Read our perspective on genetic testing for breast cancer (September 2012).* 

   

BRCA1 and BRCA2 gene mutations

BRCA1 and BRCA2 (BReast CAncer genes 1 and 2) are the most well-known genes linked to breast cancer risk. BRCA1/2 mutations can be passed to you from either parent and can affect the risk of cancers in both women and men.  

A person who has a BRCA1/2 mutation is sometimes called a BRCA1 or BRCA2 “carrier.”  

Like other gene mutations, BRCA1/2 mutations are rare in the general population. In the U.S., between one in 400 and one in 800 people in the general population have a BRCA1/2 mutation. However, prevalence varies by ethnic group. Among Ashkenazi Jewish men and women, about one in 40 have a BRCA1/2 mutation [26].  

The table below shows how the prevalence of BRCA1 and BRCA2 mutations varies among breast cancer survivors from different ethnic groups.  

Prevalence of BRCA1 and BRCA2 mutations among women with breast cancer by ethnic group (U.S.) 

 

BRCA1 

 BRCA2 

Asian American

0.5%

Data not available

African American

1.3-1.4%

2.6%

Caucasian (non-Ashkenazi Jewish)

2.2-2.9%

2.2%

Hispanic

3.5%

Data not available

Ashkenazi Jewish

8.3-10.2%

1.1%

Adapted from National Cancer Institute materials [26-27].

 

BRCA1/2 mutations and breast cancer in women

Women who have a BRCA1/2 gene mutation have an increased risk of breast cancer [28-30]. Women who have a BRCA1 gene mutation have a 50 to 70 percent chance of developing breast cancer by age 70. For BRCA2 carriers, estimates range from 40 to 60 percent [29]. Women in the general population have about an eight percent chance of developing breast cancer by age 70 [4]. (Lifetime risk of breast cancer, defined as risk up to age 85, is about 12 percent [4].)  

This means in a group of 100 women without a mutation, about eight will develop breast cancer by age 70 (about 12 by age 85). While in a group of 100 women with a BRCA1/2 mutation, between 40 and 70 will develop breast cancer by age 70. Because these numbers represent average risk, the risk of breast cancer for any one woman with a BRCA1/2 mutation may fall outside this range.  

Together, BRCA1/2 mutations are thought to explain a large portion of hereditary breast cancers [26]. Most breast cancers, however, are not hereditary. And, many women with a BRCA1/2 mutation will never have breast cancer [28-30]. Thus, a combination of factors likely determines who will get breast cancer.  

Learn about risk-reducing options for women at higher risk.

Learn about genetic testing

Risk of triple negative breast cancer

Women who have a BRCA1 mutation are at higher risk for triple negative breast cancer, as they tend to have breast cancers that are triple negative [113-114]. Triple negative breast cancers are:

Women who have a BRCA2 mutation tend to have breast cancers that are estrogen receptor-positive (ER+) [113-114].  

Learn about hormone (estrogen and progesterone) receptor status, HER2/neu status and other factors that affect prognosis and treatment.  

Learn more about triple negative breast cancer.   

Learn about molecular subtypes of breast cancer.  

Risk of a second primary breast cancer

A BRCA1/2 mutation can increase the risk of a second primary breast cancer (a second breast tumor not related to the first one). These tumors usually occur in the opposite (contralateral) breast rather than in the same breast as the first cancer.  

For BRCA1/2 carriers, the chance of a contralateral breast cancer 10 years after diagnosis of the first cancer is about 13 to 30 percent compared to about five to 10 percent for breast cancer survivors without a BRCA1/2 mutation [115-120]. The lifetime risk of a second primary contralateral breast cancer is about 30 to 65 percent for BRCA1 carriers and about 30 to 60 percent for BRCA2 carriers [115-120]. 

 

For a summary of research studies on BRCA1 and BRCA2 mutations and breast cancer, visit the Breast Cancer Research section. 

 

BRCA1/2 mutations and breast cancer in men

 

Breast Cancer in Men
Fact Sheet

Men can also have BRCA1/2 mutations and may pass these mutations on to their children.  

Men who have a BRCA2 mutation have an increased risk of breast cancer and may also have an increased risk of prostate cancer [26,28,30,121-122]. In men, the lifetime risk of breast cancer is 1 in 1,000 for non-carriers and about 65 in 1,000 for BRCA2 carriers [119,123].  

Men who have a BRCA1 mutation may also have an increased risk of breast cancer, but this link is less clear [26].  

While five to 10 percent of breast cancers in women are considered to be due to gene mutations, up to 40 percent of breast cancers in men may be related to BRCA2 mutations [124]. This means that men who develop breast cancer are more likely to have an inherited gene mutation than women who develop breast cancer.  

Learn more about breast cancer in men.  

Learn about genetic testing.
 

BRCA1/2 mutations and ovarian cancer

BRCA1/2 mutations increase a woman's risk of ovarian cancer. For women in the general population, the lifetime risk of ovarian cancer is about two percent [125]. However, lifetime risk of ovarian cancer for BRCA1 carriers is estimated at 35 to 70 percent [125]. And, for BRCA2 carriers, this risk is 10 to 30 percent [125].  

BRCA1/2 carriers can reduce their risk of both breast and ovarian cancer by having prophylactic oophorectomy (surgical removal of the ovaries) [126]. Learn more about prophylactic oophorectomy.
 

BRCA1/2 mutations and other types of cancer

BRCA1/2 carriers may also have an increased risk of pancreatic cancer, prostate cancer and some second primary cancers (new cancers that develop after a first breast cancer). However, data are limited and these topics are still under study.   

 

For a summary of research studies on BRCA1 and BRCA2 mutations and breast cancer, visit the Breast Cancer Research section.

 

BRCA1/2 mutations and breast cancer risk factors

Many risk factors for breast cancer in women are different from those in men. Learn about risk factors for breast cancer in men.

Radiation exposure

Very low doses of radiation—such as from X-rays—do not have much, if any, impact on breast cancer risk. While the radiation during mammography can increase the risk of breast cancer over time, this increase is very slight [137-139]. However, there is some concern that radiation exposure before age 30 from screening mammography may increase breast cancer risk to a greater degree in BRCA1 and BRCA2 carriers [140]. This issue is under active study.

Other risk factors

Most risk factors for breast cancer likely impact breast cancer risk in BRCA1/2 carriers just as in non-carriers. For example, exercise and breastfeeding appear to decrease the risk of breast cancer in both BRCA1/2 carriers and non-carriers [127-128].  

However, certain reproductive and lifestyle factors may affect risk differently for BRCA1/2 carriers than non-carriers. For example:

  • Although having children and a younger age at first birth lower the risk of breast cancer in average women, some studies show no link between these factors and decreased risk among BRCA1/2 carriers [127,129-131]. And, a few studies have shown that having more children may actually increase risk in BRCA2 carriers [129-131]. 
     
  • While starting menstrual periods at an earlier age and current or recent use of birth control pills increase the risk of breast cancer overall, it is unclear whether these factors affect risk in BRCA1/2 carriers [127,130-136].
     

Support for BRCA1/2 carriers

Some support groups are tailored to BRCA1/2 mutation carriers and people with BRCA-related breast cancers. For example, FORCE and Sharsheret are organizations that have on-line support for women affected by hereditary breast and/or ovarian cancer. Our Support section offers a list of resources to help find a local or on-line support group.    

Komen Support Resources  

  • Our breast care helpline 1-877 GO KOMEN (1-877-465-6636) provides free, professional support services and help finding local support groups. Our trained and caring staff are available to you and your family Monday through Friday from 9:00 a.m. to 10:00 p.m. EST and from 6:00 a.m. to 7:00 p.m. PST. 
     
  • Our Message Boards offer online forums to share your thoughts or feelings about subjects related to breast cancer. Our Women at Higher Risk of Breast Cancer forum within the Message Boards offers women at higher risk a place to share their own unique experiences and challenges.
 

 

Talking about family health history with your provider

Your family history of breast cancer and other health conditions is important to discuss with your health care provider. This information helps your provider understand your risk of breast cancer.

The Office of the Surgeon General and the National Human Genome Research Institute (part of the National Institutes of Health, Department of Health and Human Services) created an online tool called “My Family Health Portrait” that you can use to create a chart of your family’s health history. This chart may be useful in discussions with your provider about your family history of breast cancer and/or other health conditions.

 

Finding clinical trials for BRCA1 and BRCA2 carriers

BreastCancerTrials.org in collaboration with Susan G. Komen® offers a custom matching service that can help you find a clinical trial recruiting people with a BRCA1/2 or other gene mutations. (Learn more about this program.) You can also visit the National Institutes of Health's website to find a clinical trial.

Learn more about clinical trials.  

*Please note, the information provided within Komen Perspectives articles is only current as of the date of posting. Therefore, some information may be out of date at this time.  

Updated 02/05/14

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