Genetic testing

Depending on your family history, your GP may refer you to a family history or genetics clinic, which could involve genetic testing. About one in every four women with a family history of breast cancer has an inherited fault in a BRCA gene. Currently, the NHS only offers genetic tests to people with a strong family history of breast cancer.

Some private companies offer genetic testing directly to the public. There is little evidence that direct genetic tests can predict breast cancer risk, and they usually do not test for faults in BRCA1 or BRCA2. They are also not carried out alongside appropriate genetic counselling. Breakthrough does not recommend the use of direct genetic tests.

Genetic testing through the NHS can detect faults (changes or mutations) in the BRCA1 and BRCA2 breast cancer genes that can increase the risk of developing breast cancer.

Families where there are childhood sarcomas and brain tumours as well as breast cancer can also be tested for faults in TP53. Faults in this gene can occasionally increase the risk of breast and other cancers, but are rare.

If you are eligible for genetic testing and are considering it, you should be offered genetic counselling before any testing occurs. There are two stages to genetic testing:

This involves searching the DNA of a relation in your family who has – or has had – breast cancer to see if there is a fault in one of their breast cancer genes.

Their test results should be available within 8 weeks, although it can take a little longer before they receive an appointment to get their results. The results will have implications for your relative and the rest of this side your family. Healthcare professionals will explain the result to your relative and help them decide when and how to tell the family if the results will affect them.

What a negative diagnostic test result means
A negative result from a diagnostic test means that a mutation that increases breast cancer risk was not found and that the genetic cause of any breast cancer in your family is not yet understood. In other words, the result is inconclusive.

It doesn’t, however, reduce your family’s risk of developing breast cancer – they still have a greater chance of developing the disease than the general population.

A negative mutation search result is quite common, as the mutation responsible for increasing breast cancer risk is currently only found in around 1 in 5 tests.

It means predictive testing will not be possible for other members of the family.

What a positive diagnostic result means
A positive genetic test result will mean that your relation is found to have a gene fault associated with increased breast cancer risk. This also means that doctors will understand the genetic basis of breast cancer in your family and the reasons why your family members may be at increased risk.

This means that predictive testing, which can identify inherited gene faults in relatives of people who have had mutation search tests, is now available.

There is a 1 in 2 chance that each of your relative’s siblings or children has inherited the faulty gene.

If a family gene fault is found, other family members not affected by breast cancer can have their DNA tested – if they wish.

If a gene fault is found in one of your relations, and you decide to have a predictive test, you’ll need to have genetic counselling first. The test result should be ready after two weeks, although it can take slightly longer to get an appointment to receive the result. This will show whether you have the fault or not.

What a negative genetic test result from predictive testing means
A negative result from a predictive test means the fault found in your relative was not found in you – so you’ve not inherited the increased risk of breast cancer that runs in your family. It also means that you cannot pass the fault on to your children and that you’re at the same risk of developing breast cancer as the rest of the population.

What a positive genetic test result from predictive testing means
A positive predictive test result means that you have inherited the fault found in your relative. This means your risk of developing breast cancer is increased, and you may also have an increased risk of developing other cancers. 

This also means that doctors understand the genetic basis of your increased risk.

There’s a 1 in 2 chance of you passing the fault to each of your children.

Specific tests for the Ashkenazi Jewish population
Three particular faults in the BRCA genes that increase the risk of developing breast cancer are more common in members of the Ashkenazi Jewish population. For this reason, an alternative genetic test specifically for Ashkenazi Jews is available. If you are of Ashkenazi Jewish ancestry and are worried about breast cancer in your family, speak with your GP.

To learn more about genetic testing available for people with a family history in England, Wales and Scotland, download our free publication The Best Treatment: Your guide to UK services for people with a family history of breast cancer (2397 kb)

Information last reviewed: 17 March 2011