The tests, which will start with women who have breast or ovarian cancer in 2014, aim to make genetic risk testing a standard feature of NHS cancer treatment.
The results will be used to select targeted drugs, and could influence other treatment decisions such as the extent of surgery.
Knowledge of genetic risks could also affect the health decisions of relatives of cancer patients.
The testing programme, which will be run by the Institute of Cancer Research and the Royal Marsden Hospital, London, is the first attempt to use mass genetic risk testing as a core aspect of cancer treatment.
Genetic mutations are responsible for 15% of ovarian cancers and around 2% of all cancers. The BRAC gene mutation in women increases the risk of breast cancer to as high as 80%.
The genetic tests were developed by biotechnology company Illumina.
According to Prof. Nazneen Rahman, lead investigator of the programme, knowledge of genetic risk factors “allows more personalised treatment, so for example such people are often at risk of getting another cancer and may choose to have more comprehensive surgery, or may need different medicines, or extra monitoring.”
Prof. Peter Johnson, chief clinician at Cancer Research UK, said: “This exciting new initiative will help embed genetic testing into routine NHS cancer care, and hopefully allow more cancer patients to benefit from genetic testing – and more personalised care – in the future.”