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  • What is genetic testing for breast cancer and who should get it?

    Most breast cancers are not related to genes or family history. In fact, only five to 10 percent of all breast cancers diagnosed in the U.S. are thought to be hereditary.1-3 However, if you have been diagnosed with breast cancer, you may worry about the risk to your family members. And, if a family member has been diagnosed, you may worry about your own risk. So, who really needs to be concerned about this and who should consider genetic testing? Furthermore, if you do have a breast cancer gene mutation or a strong family history, what can you do to lower your risk of developing breast cancer?  

    Talking to your health care provider is the best way to understand your (or your family’s) risk of hereditary breast cancer. Here, we cover the basics of hereditary breast cancer and genetic testing to help you discuss these topics with your provider.   

    Genes and gene mutations

    Every cell in your body contains genes. Genes contain the blueprints (genetic code) for your body. For example, they contain the information that determines the color of your eyes. They also contain information that affects the functions of your body, such as when cells grow, divide and die.  

    The information in your genes is passed on (inherited) from both your mother and your father. And, you can pass this information on to your children.  

    Some changes in the genetic code that affect the function of the gene are called mutations. Mutations can be passed on from a parent to a child. Many of these inherited gene mutations have little or no effect on health (good or bad). Others, however, can increase the risk of certain diseases, including cancer.  

    Mutations in certain genes are known to increase breast cancer risk. A family history of some cancers is also important. Having multiple immediate family members with breast or ovarian cancer can increase breast cancer risk, even when no known genetic mutation has been identified in the family.  Learn more about having a family history of breast (or ovarian) cancer and breast cancer risk

    Inherited gene mutations and breast cancer risk

    BRCA1 and BRCA2 (BReast CAncer genes 1 and 2) are the best-known genes linked to breast cancer risk. There are other less common genes that also increase risk and still others that are under study (learn more).  

    How many people in the U.S. have BRCA1 or BRCA2 gene mutations?

    BRCA1 and BRCA2 mutations are rare in the general U.S. population (about 1 in 400 people have one of these mutations). However, they are more common among certain ethnic groups. For example, among Ashkenazi (Eastern European) Jewish men and women, about one in 40 people has a BRCA1 or BRCA2 mutation.2  

    Learn more about ethnicity and the prevalence of BRCA1 and BRCA2 mutations

    BRCA1 and BRCA2 gene mutations and female breast cancer

    Women in the general U.S. population have about an eight percent chance of developing breast cancer by age 70.3 Women who have a BRCA1 gene mutation, however, have a 50 to 70 percent chance of developing breast cancer by age 70. For women who have a BRCA2 mutation, estimates of risk range from 40 to 60 percent by age 70.4 This means in a group of 100 women in the general population, about eight will develop breast cancer by age 70. While in a group of 100 women with a BRCA1 or BRCA2 mutation, between 40 and 70 will develop breast cancer by age 70. (These numbers are averages, so the risk for an individual may fall outside this range.)  

    Although women who have a BRCA1 or BRCA2 mutation have a greatly increased risk of breast cancer compared to those who do not, their risk of breast cancer is not 100 percent. Some women with a mutation will never get breast cancer.4 And, women without a mutation are still at risk (most women who develop breast cancer do not have a BRCA1 or BRCA2 mutation). 

    For those who do have a BRCA1 or BRCA2 mutation, there are steps that can lower risk and special screening guidelines to help ensure that if breast cancer does develop, it is caught early.  

    Learn more about risk-lowering options for women who have a BRCA1 or BRCA2 mutation

    BRCA1 and BRCA2 gene mutations and male breast cancer

    BRCA2 mutations (and possibly BRCA1 mutations) also increase the risk of male breast cancer.2,5-7 In the general U.S. population, about 1 in 1,000 men will develop breast cancer in their lifetime. Among men with a BRCA2 mutation however, about 65 in 1,000 will develop breast cancer.8-9  

    Although only five to 10 percent of female breast cancers are thought to be due to gene mutations, up to 40 percent of male breast cancers may be related to BRCA2 mutations.10 This means that men who develop breast cancer are more likely than women who develop breast cancer to have an inherited gene mutation. 

    Who should consider genetic testing for BRCA1 and BRCA2 mutations?

    Genetic testing gives people the chance to learn if their breast cancer or their family history of breast cancer is due to an inherited gene mutation. Breast cancer is common and BRCA1 and BRCA2 mutations are rare, so just having a close relative with breast cancer does not mean that a BRCA1 or BRCA2 mutation is present in the family. However, the more relatives with breast or ovarian cancer and the younger their ages at the time of their cancer diagnosis you have, the higher the chance that your family has a BRCA1 or BRCA2 (or other gene) mutation. Genetic testing is recommended only for certain people, including those with:11 

    • A family member (parent, sibling, child, grandparent, grandchild, uncle, aunt, nephew, niece or first cousin) diagnosed with breast cancer at age 45 or younger 
    • A family member (parent, sibling, child, grandparent, grandchild, uncle, aunt, nephew, niece or first cousin) diagnosed with ovarian cancer at any age 
    • A personal or family history of both breast and ovarian cancers on the same side of the family  
    • A personal or family history of male breast cancer  
    • Ashkenazi Jewish heritage (as well as a family history of breast or ovarian cancer)  
    • A personal history of breast cancer at age 45 or younger 
    • A personal or family history of bilateral breast cancer (cancer in both breasts)  

    A health care provider or genetic counselor can help you decide whether genetic testing is appropriate for you or your family members. Many insurance providers cover the costs of at least a large part of the testing when it is medically recommended.  

    In most cases, testing is first done on the person with breast cancer. If no mutation is found in that person, the cancer was probably not due to a BRCA1 or BRCA2 genetic mutation and other family members do not need to be tested. If a mutation is found, other family members can be tested for the specific BRCA1 or BRCA2 mutation found in the person with breast cancer. It is not likely that all family members will have the mutation. For example, if your mother has a BRCA1 or BRCA2 mutation, there is only a 50 percent chance you also have a mutation (you get half of your genes from your mother and half from your father). If no one in your family who has had breast cancer or ovarian cancer is available for testing (or if your family medical history is unknown), your provider or a genetic counselor can help you decide whether genetic testing would be informative for you. He/she can also help you decide whether testing for genes other than BRCA1 and BRCA2 might be appropriate for you.  

    Benefits and risks of genetic testing  

    Although a simple blood test is all that is needed to check for a BRCA1 or BRCA2 mutation, the benefits and risks should be considered before testing. There are potential physical, emotional and financial impacts of knowing your genetic status. Your provider or a genetic counselor can discuss these issues with you. 

    Benefits

    • You and your health care provider can better personalize your breast care plan. This may include being screened at a younger age and more often. You can also take steps (such as risk-lowering drugs or preventive surgery) to lower your risk of breast cancer. 
       
    • You can take steps to lower your risk of ovarian cancer.
       
    • You may be able to join a clinical trial of risk-lowering options for people with BRCA1 and BRCA2 mutations. Or if you have been recently diagnosed (or recently had a recurrence), you may be able to join a clinical trial of treatment for people with BRCA1 and BRCA2 mutations. BreastCancerTrials.org in collaboration with Susan G. Komen for the Cure® offers a custom matching service that can help you find a clinical trial recruiting people with BRCA1, BRCA2 or other genetic mutations. Learn more about clinical trials.  

    Risks

    • For some people, knowing they have a BRCA1 or BRCA2 mutation can cause worry and anxiety, even though they may never get breast cancer. They may also worry about an increased breast cancer risk for their siblings and children (and the anxiety it may cause those family members). For others, knowing they do not have a mutation may give a false sense of security of not being at risk for breast cancer, and as a result may not get routine breast cancer screening. (All women should get routine breast cancer screening to lower their risk of dying from breast cancer.)
       
    • Although there are laws to help protect against genetic discrimination, there are some limits. The Genetic Information Nondiscrimination Act (GINA) prevents health insurers from denying coverage or charging higher premiums if your genetic profile puts you at higher risk for breast cancer. It also protects against genetic discrimination from employers. However, GINA does not prevent life insurance providers or disability insurance providers from denying coverage. 

    At-home genetic testing

    You may have seen ads for at-home genetic testing kits. These kits are not recommended for assessing breast cancer risk. The U.S. Food and Drug Administration, U.S. Federal Trade Commission and Centers for Disease Control and Prevention all caution against the use of at-home testing kits. The results of any genetic test should be interpreted by a trained health care provider or genetic counselor.12-14 

    Conclusions

    Although only about five to 10 percent of breast cancers in the U.S. are thought to be hereditary, for people who have a BRCA1 or BRCA2 gene mutation, the risk of breast cancer is greatly increased. Most women, even most breast cancer survivors, have only a small chance of having a BRCA1 or BRCA2 gene mutation. Those who test negative for a mutation still have a risk of breast cancer based on other factors (learn more). 

    If you are considering genetic testing, it is important to talk to your health care provider or a genetic counselor. These trained medical professionals can help you determine whether testing for BRCA1 and/or BRCA2 mutations is appropriate for you.  

    Komen’s role in research on hereditary breast cancer 

    Susan G. Komen for the Cure®’s Research and Scientific Programs provide support for research from the roles BRCA1 and BRCA2 genes play in the development of cancer to designing treatments specific to BRCA1 and BRCA2 related breast cancers.  

    Dr. Judy Garber, MD, MPH, Director of the Cancer Risk and Prevention Clinic at Dana-Farber Cancer Institute and Komen Scholar offers a nice take home message from all of the information presented in this article. “It has been more than 15 years since the BRCA1 and BRCA2 genes were identified. In that time, women have fought to make genetic information available to those who would use the information to try to reduce the risks of breast and ovarian cancers, in particular, for themselves and their family members. Ongoing research has helped to:  

    1) provide better estimates of breast and ovarian cancer risk in people with BRCA1 and BRCA2 mutations 

    2) identify better breast cancer screening strategies for people with BRCA1 and BRCA2 mutations 

    3) identify strategies to lower the risk of breast and ovarian cancers in women with BRCA1 or BRCA2 mutations 

    4) explore more effective ways to treat BRCA-related breast cancers  

    5) ensure genetic testing is conducted responsibly with appropriate counseling for patients and family members" 

    None of this research would be possible without the dedication of people who participate in these clinical trials. On behalf of her fellow researchers Dr. Garber added, “We thank our patients for their commitment to this research, all over the world." 

    Komen has invested more than $24 million in research focused on BRCA1/2 genes through our various grant mechanisms, including a Promise Grant focused on breast cancer prevention in people who have BRCA1 or BRCA2 mutations.  

    Learn more about the research we are funding.   

    Learn more about Komen’s research on BRCA1/2 and hereditary breast cancer

     

    References

    1. American Cancer Society. Cancer Facts & Figures 2012. American Cancer Society, 2012.  
    2. National Cancer Institute. Genetics of breast and ovarian cancer (PDQ). http://www.cancer.gov/cancertopics/pdq/genetics/breast-and-ovarian/HealthProfessional, 2012.  
    3. American Cancer Society. Breast Cancer Facts & Figures 2011-2012, 2011.  
    4. Chen S, Parmigiani G. Meta-analysis of BRCA1 and BRCA2 penetrance. J Clin Oncol. 25(11):1329-33, 2007. 
    5. Struewing JP, Hartge P, Wacholder S, et al. The risk of cancer associated with specific mutations of BRCA1 and BRCA2 among Ashkenazi Jews. N Engl J Med. 336: 1401-8, 1997.  
    6. Antoniou AC, Cunningham AP, Peto J, et al. The BOADICEA model of genetic susceptibility to breast and ovarian cancers: updates and extensions. Br J Cancer. 98(8):1457-66, 2008. 
    7. Fentiman IS, Fourquet A, Hortobagyi GN. Male breast cancer. Lancet. 367(9510):595-604, 2006.  
    8. Isaacs C, Peshkin BN, Schwartz M. Chapter 19: Genetic Testing and Management of Patients with Hereditary Breast Cancer, in Harris JR, Lippman ME, Morrow M, Osborne CK. Diseases of the Breast, 4th edition, Lippincott Williams & Wilkins, 2010. 
    9. Liede A, Karlan BY, Narod SA. Cancer risks for male carriers of germline mutations in BRCA1 or BRCA2: a review of the literature. J Clin Oncol. 22(4):735-42, 2004.  
    10. Thorlacius S, Sigurdsson S, Bjarnadottir H, et al. Study of a single BRCA2 mutation with high carrier frequency in a small population. Am J Hum Genet. 60(5): 1079–1084, 1997.  
    11. National Comprehensive Cancer Network. NCCN Clinical practices guidelines in oncology: Breast cancer risk reduction. V.1.2012. http://www.nccn.org, 2012.  
    12. U.S. Food and Drug Administration. Cracking down on health fraud. http://www.fda.gov/Drugs/EmergencyPreparedness/BioterrorismandDrugPreparedness/ucm137261.htm, 2010. 
    13. U.S. Federal Trade Commission. Facts for consumers—At-home genetic tests: a healthy dose of skepticism may be the best prescription. http://www.ftc.gov/bcp/edu/pubs/consumer/health/hea02.shtm, 2006. 
    14. Centers for Disease Control and Prevention. Genomic testing. http://www.cdc.gov/genomics/gtesting/index.htm, 2012. 

    Posted September 27, 2012