At a glance

Also known as

Breast cancer gene 1 and 2

Why get tested?

To assess the risk of developing breast or ovarian cancer associated with inheriting mutations in the BRCA1 or BRCA2 genes

When to get tested?

Genetic testing of an unaffected person for a BRCA1 or BRCA2 mutation is generally not recommended unless a mutation has already been identified in a family member.

Genetic testing is offered only through a family cancer clinic. If a woman is referred to a family cancer clinic, the availability, limitations, potential benefits, and possible consequences of genetic testing will be discussed with her.

Sample required?

A blood sample drawn from a vein in the arm

Confused about genetics?

See our Genetics Information page
 

What is being tested?

BRCA1 and BRCA2 are two tumour suppressor genes. Normally, these genes help prevent cancer by producing proteins that repair damage to DNA (the genetic material in a cell). Certain changes (mutations) in these genes disrupt the function of the protein product and are associated with hereditary breast and ovarian cancers.

According to Cancer Australia, using statistics from the Australian Institute of Health and Welfare, about 17,000 women in Australia are diagnosed with breast cancer each year (15,902 in 2013 and it is estimated to be 18,000 in 2018) and about 1,500 women with ovarian cancer. In most of these women, their cancers are sporadic, but about 5-10% of these women have a familial predisposition to breast/ovarian cancer. Approximately 20% of the familial breast/ovarian cancer (i.e. 1-2% overall) are due to a harmful mutation in the BRCA1 or BRCA2 gene.  Men can also inherit an increased risk of developing breast cancer, occasionally from mutations in BRCA1, but primarily from mutations in the BRCA2 gene.

The BRCA1 and BRCA2 genes are present in every cell of the body. To detect mutations in the genes, DNA needs to be extracted from cells, and blood is the most easily accessible source of that DNA. 

How is the sample collected for testing?

The test for BRCA mutations is done on a blood sample collected by needle from a vein in the arm. The test does not require surgical biopsy of breast or ovarian tissue.

The Test

How is it used?

There are hundreds of different BRCA1 and BRCA2 mutations that have been reported. In most patients with a strong family history of breast/ovarian cancer, it is necessary to first test an affected individual in the family to determine whether the predisposition to breast/ovarian cancer in the family is due to a BRCA1/2 mutation, and if so, what the particular mutation in the family is. This is known as diagnostic testing. Once the ‘familial mutation’ is found, other family members can then be tested for that specific mutation to determine their personal cancer risk. This is known as pre-symptomatic testing, and helps the patient with deciding whether to take steps such as prophylactic surgery that may reduce the likelihood of developing breast or ovarian cancer in the future.

When is it requested?

If a BRCA1 or BRCA2 mutation has been identified in a family member with breast and/or ovarian cancer, then that specific mutation can be tested in other family members to assess their risk. Specific BRCA1 and BRCA2 mutations are associated with some ethnic groups, such as those of Ashkenazi Jewish descent, and can be used to evaluate the risk of individuals in this group.

Someone who is considering testing should talk to their healthcare practitioner and seek counselling by a genetics educator/counsellor prior to and after testing.
 

What does the test result mean?

The degree of risk conferred with a positive result is difficult to quantify for a specific person. Results must be interpreted in conjunction with the tested person's personal and family history. A genetic counsellor or familial cancer specialist should explain the meaning of the results, explain treatment options for the individual that are intended to decrease risk, and testing options for other family members.

A negative result does not mean that a woman will not develop breast or ovarian cancer. It simply indicates that the person tested is not at increased risk for developing hereditary breast cancer or ovarian cancer related to the BRCA mutations for which he/she was tested. Genetic testing for BRCA1 and BRCA2 mutations cannot detect 100% od these mutations; thus, even with a negative result there is a very small chance that there is a BRCA1/BRCA2 gene mutation present that was not identified by the testing method utilised. It is important to remember that more than 95% of breast cancers are not associated with a BRCA mutation. Furthermore, in the general population, the lifetime risk of developing breast cancer is approximately 10% and the lifetime risk of developing ovarian cancer is about 1%.

The presence of a BRCA1 or BRCA2 mutation means that the person tested is at an increased risk for breast and/or ovarian cancer, but it does not mean that she will definitely develop cancer. Even within a family with the same BRCA mutation, not everyone will develop cancer and those that do may develop it at different times during their life. According to the National Cancer Institute, estimates of lifetime risk for breast cancer in women are 55% to 65% for BRCA1 mutation and 45% for BRCA2 mutation. Risk of ovarian cancer is 39% with BRCA1 mutation and 11% to 19% with BRCA2 mutation.

Is there anything else I should know?

Positive test results may have implications for other family members. When one member of a family is tested for BRCA mutations, issues often arise about how or whether to share this information with other family members. Seek advice from a genetic counsellor about communication of results with other family members.

Pre- and post-test consultation with a health care provider knowledgeable about genetic testing cannot be overemphasised. There are many issues to be considered when preparing for a genetic test and upon learning the results, and a genetic counsellor has the knowledge and expertise to help sort through them.

Common Questions

If the BRCA test is positive, what are my treatment options?

If the BRCA mutation test is positive, the options include more frequent cancer screenings and screening starting earlier in life (e.g., mammography, breast MRI, blood tests for CA-125 or CA 15-3, or transvaginal ultrasonography), medications that could reduce risk (e.g., tamoxifen), or surgical removal of the ovaries or breasts. There are a number of variables involved and it is important to discuss your options with your healthcare provider and genetic counsellor.
 

If the test is positive, how likely am I to get breast or ovarian cancer?

See the previous section "What does the test result mean?"

If the test is negative, how likely/unlikely am I to get breast or ovarian cancer?  

A negative result does not completely exclude the possibility of developing breast or ovarian cancer. See the previous section ‘What does the test result mean?’ for more information. 

Where can I get this test?

The test can be requested by specialists in familial cancer clinics or clinical geneticists if it is considered appropriate and should be accompanied by pre- and post-test genetic counselling. These services are available across Australia, and can be accessed by referral from your general practitioner. The blood sample will be sent to a laboratory that specialises in genetic testing.


Last Review Date: February 4, 2018