My Breakthrough
Genetic testing
Genetic testing looks for changes or mutations in the genes that are currently known to increase the risk of getting breast cancer. As with screening for breast cancer, this does not prevent the disease.
- What are the advantages and disadvantages of having a genetic test?
- Who can be tested?
- What genetic tests are currently available for hereditary breast cancer?
What are the advantages and disadvantages of having a genetic test?
Advantages:
- Finding the gene change (mutation) that runs in a family allows blood relatives to find out whether they have inherited the increased risk of breast cancer or not.
- Finding out if you or a family member carries a gene mutation may make decision making easier.
- It is thought that some treatments may work better in cancers caused by certain gene changes. If you do develop breast cancer, then knowing the genetic reason may mean that in the future you can participate in clinical trials of these treatments.
Disadvantages:
- The results of many genetic tests are inconclusive.
- Although there is a current ban on the use of genetic information for insurance purposes, it has not yet been decided whether your genetic test results can be used when insurance premiums are set in the future.
Who can be tested?
Genetic testing is currently only suitable for people with a strong family history
of breast cancer.
Genetic testing for a family consists of 2 stages:
Mutation searching
Firstly, the DNA of an affected relative (that is someone in the family who has or has had breast cancer) is searched to find if there is a mutation in one of the 'breast cancer' genes. An affected relative has genetic testing first as any gene mutation that is causing disease in the family is more likely to be found in their DNA. This is known as mutation searching.Mutation testing or Predictive testing
Secondly, if a family mutation is found, then DNA from unaffected relatives (that is family members who have not had breast cancer) can be tested. This is a choice that each family member makes for themselves. Results will show whether they have the family mutation that makes them more likely to get breast cancer. This is known as mutation testing or predictive testing. If this type of test shows that a family member does not carry the family mutation identified through mutation searching, then their risk becomes the same as the general population.
What genetic tests are currently available for hereditary breast cancer?
- BRCA1 (Breast Cancer 1)
- BRCA2 (Breast Cancer 2)
Genetic testing is available for mutations in both of these genes.
Inherited mutations in another gene, TP53 (Tumour Suppressor protein 53), can cause Li-Fraumeni syndrome and can give an increased risk of breast cancer. This is much rarer than mutations in the BRCA genes. Families in which there are childhood sarcomas and brain tumours as well as breast cancer can be offered genetic tests for mutations in TP53.
There are extremely rare mutations in other genes involved in hereditary breast cancer that are also known and almost certainly more that are yet to be discovered. It is likely that some of these unknown genes are influenced by lifestyle factors. Genetic tests are not available for these at present.
