Individuals with a strong family history of breast cancer or ovarian cancer may want to know if they have an inherited tendency to these cancers. Sometimes a very young onset of breast cancer may also indicate a likely BRCA1/2 gene mutation. For example a woman diagnosed with a triple negative breast cancer in her early 30s may have a BRCA-1 gene mutation even if she does not have an obvious family history of cancer.Note: the most useful prediction of risk from a BRCA1/2 test in an unaffected person is when a BRCA1/2 mutation has already been found in a relative with breast or ovarian cancer. Without this information, a negative BRCA1/2 test result is often not very informative. There are therefore two types of BRCA1/2 testing; ‘diagnostic’ and ‘predictive’ testing.Diagnostic BRCA1/2 testing. This test is done in someone who has had a breast or ovarian cancer, usually in the context of a strong family history. It can give you information about chances of further cancers and can provide family members with the information to have a predictive test.Predictive BRCA1/2 testing. This test is done in an unaffected relative of someone who is known to have a BRCA1/2 gene mutation. If you are a child or sibling of this person there will usually be a 50:50 (1 in 2 or 50% chance) that you have, or have not, inherited the mutation.Such testing may be useful to help you decide whether to take steps that may prevent breast or ovarian cancer from developing, or may pick it up at an early and more treatable stage. There are a complex range of options available, ranging from more frequent mammograms to surgical removal of the organs at risk and you should discuss these in detail with a clinical genetics professional before deciding whether testing would be helpful or right for you. Your GP can refer you to your local clinical genetics service. (see “Is there anything else I should know?” below).
