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Genetic Testing

Learn about genes and cancer, signs of hereditary cancer, genetic counseling, types of genetic tests and what results mean for you and your family.

Overview

Genetic testing involves taking a sample of blood, cheek swab, or tissue in order to analyze a person’s genes. Genetic testing can be used to determine if someone has a change in their genes (mutation) that make them more likely to develop certain diseases such as cancer. Tests that measure likelihood for a disease are called “predictive genetic tests.” 

BRCA1 and BRCA2 are the most common genes involved in hereditary breast and ovarian cancers. Testing can be performed on either a blood or cheek swab sample to tell if a person has one of these BRCA mutations. This test does not detect whether a person has cancer or not; it indicates whether a person carries a change in one of these genes which can increase cancer risk.

Genetic testing can be complex: 

  • Results may affect health care recommendations
  • The decision to undergo genetic testing is a very personal one, and the benefits and limitations depend on your unique circumstances. 
  • Ordering the test and interpreting test results is not straight-forward

For these reasons, it is important to speak with a specialist in cancer genetics if you are concerned that cancer may run in your family or if you are interested in genetic testing.

BRCA 1 and BRCA 2 genetic testing

The two genes most commonly associated with hereditary breast and ovarian cancer are called BRCA1 and BRCA2 (for Breast Cancer 1 and Breast Cancer 2 genes).  A blood or cheek swab test is available that can tell if a person carries a mutation in one of these genes. 

There are different types of BRCA tests that can be ordered, each looks for mutations at different sites along the genes. It's important that the correct test is ordered or the results may not be meaningful. A genetics expert will assure that the proper test is ordered. 

The first person in a family to have genetic testing will usually have “full-sequencing” of the BRCA1 and BRCA2 genes, which means the lab examines the entire DNA of both genes to see if there is a known cancer-causing mutation in one of these genes. The cost of this test is about $2500. 

If a mutation has already been identified in a family, then often (but not always) a “single-site” test can be ordered to look for the specific mutation that was already found. The cost of this test is about $300. 

In certain populations (for example, people of Eastern European Jewish descent) there are specific BRCA mutations called “founder mutations” that  occur more frequently. For members of these populations, it may be possible and cost effective to order tests that first look for these common mutations. These “single-site” and “founder-mutation” tests are less expensive tests than “full sequencing," about $300.   

BART (BracAnalysis Rearrangement Test) is a panel that looks for specific rare genetic mutations known as "large rearrangements" that cannot be detected on regular BracAnalysis testing through Myriad. BART testing is usually recommended in families that have a suspicious history of cancer but no identified mutation on comprehensive BRCA testing. Families from certain ethnicities including Latin Ameria, Caribbean, and Near and Middle Eastern background are more likely to test positive for a BART mutation. This test is about $700. A genetics expert can help you and your family determine if BART testing would be of benefit.

Insurance will usually cover the cost of genetic testing.  See our page on insurance coverage for more information.

In the United States, BRCA results are usually available in 2-3 weeks. Under some circumstances—for individuals newly diagnosed with cancer, for whom test results may affect treatment choices—the test can be run more quickly for an additional cost. In some countries, the results of BRCA testing can take significantly longer.  The results may also take longer if testing is ordered as part of a research study.

Benefits and limitations of genetic testing

BRCA testing can provide important medical information for the person undergoing the testing and for his or her family members. Some benefits of genetic testing for women already diagnosed with cancer include:

  • It can help women diagnosed with breast cancer make treatment decisions such as whether to undergo lumpectomy and radiation or bilateral mastectomy.
  • It can help women diagnosed with cancer understand their risk for a second, new cancer and make informed risk management decisions.
  • It can help family members who have not had cancer better understand their risk for cancer. Testing someone with cancer in the family first increases the likelihood of an informative genetic test result.

Some benefits of genetic testing for people who have not been diagnosed with cancer include:

  • Testing negative under certain circumstances may mean that the person did not inherit an elevated risk for cancer.
  • It can help people better understand and manage their cancer risk.

BRCA testing is not right for everyone, and the test itself has limitations including: 

  • It does not always provide a simple "yes" or "no" answer about hereditary cancer risk within a family. There are test results that are "uninformative" which do not provide any additional information about a family's cancer risk
  • Not everyone is a candidate for genetic testing
  • Testing can be expensive if not covered by insurance

An expert in cancer genetics will explain the benefits and limitations further and determine whether or not genetic testing is appropriate and likely to give a person further information about his or her cancer risk.

BRCA prevalence

BRCA mutations can occur in any population; mutations have been found in people of all ethnic backgrounds. People of certain ethnicity are more likely to carry BRCA mutations, but any family can have a mutation.

Experts estimate that, in the general population, one in every 300 to 500 people harbors a BRCA mutation. Mutations are most common in people of Eastern European (Ashkenazi) Jewish descent.  About one in every 40 people of Ashkenazi Jewish descent (2.5% of this population) carries a BRCA mutation. Members of certain other ethnic groups may also be more likely than those in the general population to carry a BRCA mutation. Various factors—such as the number of people with cancer, their relationship to each other, age of onset of cancer, and types of cancer—affect the likelihood of a BRCA mutation within a family. A specialist in cancer genetics can look at your heritage and family history, and help determine the likelihood that your family has a BRCA mutation.

Types of test Results

BRCA testing can yield three possible results:

  • a positive test result
  • a negative test result 
  • a “variant of uncertain significance” (VUS)  

A positive BRCA test result indicates that a “deleterious mutation” was found in either the BRCA1 or BRCA2 gene (or, rarely in both genes).  This means that a change was found in the gene which is known to increase the risk for cancer.  A negative BRCA test result means that no such gene mutation was found. A “variant of uncertain significance” means that a change was found that may or may not increase the risk for cancer. 

Genetic testing may have a wide range of effects on people and their families.  Some people need additional support from psychologists or other health-care professionals to help them work through the consequences of their test results.  Most genetics specialists work with mental-health care professionals who are skilled in helping people cope with genetic test results.  Some people find it helpful to speak with others who have had genetic testing.  FORCE has a rich community of members who have had personal experience with genetic counseling, genetic testing and hereditary cancer.  

It is important to consult a genetics expert to help interpret and explain genetic test results and provide management recommendations. 

Positive test results

A woman who tests positive for a BRCA mutation has an increased lifetime risk for breast and ovarian cancer and certain other cancers compared to women in the general population.  Even with a gene mutation, a woman's risk for cancer is not 100%; it is possible to have a BRCA mutation and never develop cancer. A positive BRCA test may affect treatment options for women diagnosed with cancer, and can affect screening, and risk-reduction options for women who have not had cancer.  It is important to have a health care team that is experienced in managing  hereditary cancer risk.  For more information visit our section on risk management options.

A man who tests positive for a BRCA gene mutation may be at higher risk for male breast cancer, prostate cancer, and other cancers compared to men in the general population.  However, it is possible for a man to have a BRCA mutation and never develop cancer.  It is important for a man who tests positive for a mutation to have a health care team that is experienced in monitoring men with BRCA mutations.

A positive test in either a man or woman means that other relatives may also have inherited the same mutation.  BRCA mutations can be passed on from the father or mother to sons or daughters. There is a 50% chance that a parent will pass on a mutation to each of their children. It is important to discuss with a specialist in cancer genetics who in the family may be at risk, and who should be informed of genetic test results. For more information visit our page on sharing family medical information.

People with a BRCA mutation may be eligible for research studies to help prevent, detect, or treat hereditary cancer. For more information visit our page on research studies.

Negative test results

A negative BRCA test result can have several different meanings depending on the individual and family circumstances of the person tested.

In a family where a BRCA mutation has already been identified, a negative test may be considered a "true negative." This means that the person does not have a higher risk for breast or ovarian cancer than the general population. In a family with a known mutation, screening recommendations are different for someone who tests BRCA negative than for someone who tests positive.  However, since cancer is a common disease and since most cancer has no known cause, a negative genetic test does not guarantee that a person won’t develop cancer in his or her lifetime.

For some individuals who test negative for BRCA 1 and BRCA 2 mutations on BracAnalysis, there is an expanded test that can be run to look for mutations not found in standard testing. "BART" (BracAnalysis Rearrangement Test) is a panel that looks for specific rare genetic mutations known as "large rearrangements" that cannot be detected on regular BracAnalysis testing through Myriad. BART testing is usually recommended in families that have a suspicious history of cancer but no identified mutation on comprehensive BRCA testing. Families from certain ethnicities including Latin Ameria, Caribbean, and Near and Middle Eastern background are more likely to test positive for a BART mutation. This test is about $700.

Sometimes hereditary breast and ovarian cancers can be caused by changes in genes other than BRCA1 or BRCA2. Mutations in other genes will not show up in a BRCA test.  There are tests for some of these other genes. A negative BRCA test in a family without an identified mutation is called an "uninformative negative" test result. Members of families with no known BRCA mutation but many cases of cancer in the family may still be at high-risk for cancer. They may also qualify to participate in research looking for other genes that might be linked to hereditary cancers.  For more information please visit our page on participating in research.

A specialist in cancer genetics can interpret a negative test result and help you determine whether another genetic test may be appropriate for a your family. For more information visit our page on other hereditary cancer syndromes.

Variants of uncertain significance

Genes tell our bodies which proteins to make. Not all changes in genes are bad. Some gene changes can mean the difference between black hair and blonde hair, or the difference between brown eyes and green eyes.  Other gene changes, called mutations, can cause our body to make proteins that don’t work correctly. Some people receive a BRCA test result called a “variant of uncertain significance.”  This means that, at the time of testing, the laboratory cannot determine whether the gene change is a “deleterious change,” which increases the risk for cancer, or a variant which does not increase cancer risk. Over time, as more family members are tested for the variant, sometimes the laboratories will determine whether or not these changes are “deleterious” and will “reclassify” the test result.  It is important for people who test positive for a variant of uncertain significance to stay in contact with their genetics specialist to learn if their variant has been reclassified to a deleterious or a harmless mutation. There are research studies looking at whether variants are “deleterious” or harmless.  For more information visit our page on participating in research. Cancer screening and risk management recommendations for people who test positive for a variant of uncertain significance are usually different than recommendations for people who test negative and for people in the general population.

Uninformative tests

Sometimes variants of uncertain significance results are considered “uninformative tests” because they don’t provide additional information about a person’s cancer risk. Certain negative test results may also be considered uninformative.  In families where there is a strong family history of cancer, the preference is to test someone who has had cancer first.  In such a family, if there is no cancer survivor to test first, a negative test may be considered uninformative because it may mean any one of three very different things:

  • there is a mutation in the family and the person who was tested doesn’t carry that mutation
  • the cancer in the family is not hereditary and is instead sporadic cancer
  • the cancer in the family is due to a mutation in a different gene or in a gene which has not yet been discovered and for which there is no available test 

It is important to consult a genetics expert to help explain uninformative genetic test results and provide screening recommendations for people with an uninformative test result. 

Genetic test panels

Since the Supreme Court invalidated gene patents, several laboratories have begun to offer gene panels that test for BRCA and other genes associated with hereditary cancer risk. FORCE recommends consulting with a qualified genetics professional prior to undergoing genetic testing to assure that the appropriate tests are ordered and interpreted correctly.