Genetics tests can only be done for people who may have one of the cancer susceptibility genes that have been identified.
So far, only a few of the genes involved in hereditary cancer risk have been identified and can be tested for. These include some of the genes that affect the risk of bowel/womb cancer, breast/ovarian cancer and a few other rare conditions. We have more information on specific cancer types and genetics.
If you have several cases of other types of cancer in your family, there probably won’t be a genetic test available to you. But you may be offered the chance to take part in research that is trying to identify more cancer genes, or that is testing ways of preventing cancer. A blood sample may be taken and kept so it can be tested for genetic changes that may be identified in the future. You’ll be asked whether you agree to your blood being stored for this purpose.
You can usually only be offered a genetic test to look for a gene fault if you have a living relative who has been diagnosed with cancer and is willing to be tested first. This is because if there is a cancer susceptibility gene in a family, you won’t definitely have inherited it. If a person has a faulty gene, there is a 50% (1 in 2) chance that they will pass it on to their child. So someone in your family who has been diagnosed with cancer is tested first to find out whether they have a genetic cancer susceptibility.
The test will also look for what the particular gene fault is. Relatives can then be tested for that particular gene fault, once it is known to be the cause of the susceptibility in the family.
There is one exception to this. If you have Ashkenazi (Eastern European Jewish) or Polish ancestry, which are communities where a common gene mutation has been found, you may be offered testing without a relative who has developed cancer being tested first.