There are major implications when looking for a faulty gene that may run in the family. The relatives of people who have had cancer may wish to be tested to see if they too carry the gene, especially the daughters of women who have had breast or ovarian cancer. However, prior to being tested, it is important to discuss the pros and cons because genetic testing does not necessarily bring certainty, but does bring alot more information - mostly 'probability-type' information.
We now know about many of the genes involved in cancer and can identify the faults in these genes. For example, the BRAC1 and BRAC2 genes associated with breast (and ovarian) cancer can have very subtle changes involving only one change in the sequence. Genes consist of individual sequences within the DNA of nucleotides made of nucleic acids including cytosine, adenine, guanine and thymine (CAGT). So, a gene is a short section of DNA and each gene codes for a specific amino acid (building blocks of proteins) to be manufactured by the cell.
The BRAC gene consists of around 100,000 CAGTs and the change associated with cancer is just one single letter, which can happen anywhere in the length of the strand. As Consultant Clinical Genetic Oncologist, Dr James Mackay says, "This is a very subtle spelling mistake".
Ensuring high quality results from Genetic Testing
Genetic testing is still in its infancy and is subject to huge technical challenges, not least of all because of the sheer amount of information that is produced even from just a single sequence. Handling this level of data is a science in itself and is also prone to error. UK laboratory quality assurance systems are therefore stringent and insisting that labs offering these tests conform to ISO 15189 to ensure patient safety.
A Family Concern
For anyone with a concern due to a family history there are two basic stages to genetic testing. Firstly the affected family member would be tested to see if they have a faulty gene, and then other people in the family can be tested. However, it is essential in all cases that people have accurate information on the limitations of this diagnostic approach, the accuracy of the clinical information, the likely outcomes, what the test will show and what they might decide to do about it.
Getting your Genes Tested
Latest genetic tests available from The London Breast Clinic can now analyse 25 genes from a single blood sample. The Endo Predict test adds even further important information as it can help the breast cancer team to predict whether or not a patient will respond to hormone treatment alone - or whether they will also require chemotherapy.
See also London Breast Clinic consultant Mr Simon Marsh