Cancer is not usually inherited, but some types – mainly breast, ovarian and prostate cancer – can be strongly influenced by genes and can run in families.
We all carry certain genes that are normally protective against cancer – they correct any DNA damage that naturally occurs when cells divide.
Inheriting mutated versions or 'variants' of these genes significantly raises your risk of developing cancer because the altered genes cannot repair the damaged cells, which can build up and form a tumour.
BRCA1 and BRCA2 are two examples of genes that raise your cancer risk if they become altered. Having a variant BRCA gene greatly increases a woman's chance of developing breast cancer and ovarian cancer. This was the reason Angelina Jolie had breast cancer surgery. They also increase a man's chance of developing breast cancer and prostate cancer.
But BRCA genes are not the only cancer risk genes. Researchers recently identified more than 70 new gene variants associated with an increased risk of breast, prostate and ovarian cancer. Individually, these new gene variants only slightly increase the risk of cancer, but a 'bad' combination could mean a high risk overall.
If you or your partner have a high-risk cancer gene, such as an altered version of BRCA1, it can be passed on to any children you have.
If you're concerned, read on. This page covers:
What to do if you're worried
If cancer runs in your family and you're worried you may get it too, you may be eligible for an NHS genetic test that will tell you whether you have inherited one of the cancer risk genes.
This is known as predictive genetic testing. It's 'predictive' because a positive result means you have a greatly increased risk of developing cancer. It doesn't mean you have cancer or are definitely going to develop it.
Pros and cons of having a predictive genetic test
Not everyone who is eligible for the NHS test will want to have it. It is a personal decision, and should only be made after you've had genetic counselling sessions and talked through what having the test means, how you may feel and how you will cope.
- a positive result means you can take steps to manage your risk of developing cancer – you can make certain lifestyle changes to lower your risk, have regular screening and take preventative drugs or have preventative surgery (see Managing your risk, below)
- knowing the result may help reduce any stress and anxiety that comes from not knowing
- the results of some genetic tests are inconclusive – doctors may identify a variation in a gene but not know what effect it may have
- a positive result may cause permanent anxiety – some people would rather not know about their risk and only want to be told if they actually develop cancer
What predictive gene testing involves
There are two steps to genetic testing:
- A relative with cancer has a diagnostic blood test to see if they have a cancer risk gene (this must happen before any healthy relatives are tested). Their result will be ready six to eight weeks later.
- If your relative's test is positive, you can then have the predictive genetic test to see if you have the same faulty gene. Your doctor will refer you to your local genetics service for the blood test (you'll need a copy of your relative's test results). The result will take up to 10 days from blood sampling, but most departments won't draw blood at a first appointment.
The charity Breakthrough Breast Cancer explains the importance of these two steps:
"Without looking at the genes of an affected relative first, testing a healthy individual would be like reading through an entire book looking for a spelling mistake without knowing where the mistake is, or if there is a mistake at all."
Predictive testing is the equivalent of looking for a spelling mistake in a book when it is already known what page and line number to look at.
What a positive gene test result means
If your predictive genetic test result is positive, it means you have a mutated gene that raises your risk of developing cancer.
It doesn't mean you are guaranteed to get cancer – your genes only partly influence your future health risks. Other factors, such as your medical history, your lifestyle and your environment, also play a role.
If you have one of the mutated BRCA genes there is a 50% chance you will pass this on to any children you have and a 50% chance that each of your siblings also has it.
You may want to discuss your results with other members of your family, who may also be affected. The genetics clinic will discuss with you how a positive or negative result will affect your life and your relationships with your family.
Your doctor is not allowed to tell anyone that you have taken a genetic test or to reveal the result without your permission.
Insurance companies cannot ask you to disclose results of predictive tests for certain policies - please check conditions.
Managing your risk
If your test result is positive, you have a range of options to manage your risk. Risk-reducing surgery is not the only option.
Ultimately, there is no right or wrong answer about what you should do – it's a decision that only you can make.
Regularly examining your breasts
If you have the mutated BRCA1/2 gene, it's a good idea to be aware of changes in your breasts and feel your breasts regularly for any lumps.
This advice applies to men with a faulty BRCA2 gene too, as they are also at increased risk of breast cancer (although to a lesser extent).
In the case of breast cancer, you may wish to rely on annual screening in the form of mammograms and MRI scans to monitor your condition and catch cancer early if it does develop. Learn more about breast cancer screening.
Detecting breast cancer at an early stage means it may be easier to treat. The chance of making a full recovery from breast cancer, especially if it is detected early, is relatively high compared with other forms of cancer.
Unfortunately, there is currently no reliable screening test for ovarian cancer or prostate cancer. Read more about screening for prostate cancer.
Changes in your lifestyle can reduce your individual cancer risk. These include taking plenty of exercise and eating a healthy diet.
If you have a mutated BRCA gene be aware of other factors that could increase your risk of breast cancer. It's recommended you avoid:
- the oral contraceptive pill if you are over 35
- hormone replacement therapy
- drinking above the recommended daily amounts of alcohol
- being overweight
Learn how to [reduce your breast cancer risk] and read about the things that may help prevent ovarian cancer.
NICE recently recommended drug treatment with tamoxifen or raloxifene for a specific group of women who have a high risk of developing breast cancer. These drugs can help reduce risk.
Risk-reducing surgery means removing all the tissue (such as the breasts or ovaries) that could become cancerous. Carriers of a faulty BRCA gene may wish to consider a preventative mastectomy (removal of all the breast tissue).
Women who have risk-reducing mastectomies reduce their risk of developing breast cancer to less than 5% over their lifetime, which is less than the risk in the general population. However, a mastectomy is major surgery and recovering from it can be emotionally difficult.
Surgery can also be used to reduce ovarian cancer risk. Women who have their ovaries removed before the menopause not only dramatically reduce their risk of developing ovarian cancer, but also reduce their risk of developing breast cancer by up to 50%, even when hormone replacement therapy is given. However, this will mean you're not able to have your own children (unless you store eggs or embryos). Read more about the operation, including the risks and after-effects.
The risk of ovarian cancer in women who carry a BRCA gene fault does not begin to rise significantly until about the age of 40. Therefore, carriers who are younger than 40 will usually need to wait to have this operation.
Telling close relatives
Your genetics unit will not approach your relatives about your result – it will usually be up to you to tell your family.
You may be given a standard letter to share with relatives, which explains your test result and contains all the information they need to be referred for the test themselves.
However, not everyone will want to have the genetic test. Women who are closely related to you (for example your sister or daughter) can have cancer screening without having to undergo genetic testing.
Planning a family
If your predictive genetic test is positive and you want to start a family, you have several options. You can:
- Have your children without any intervention, and risk your child inheriting the mutation.
- Adopt a baby.
- Use donor eggs or donor sperm (depending on who is the carrier) to avoid passing on the mutation.
- Have prenatal testing, which is a test done in pregnancy that reveals whether your baby has the mutation. You can then plan to continue or terminate the pregnancy depending on the test result.
- Have pre-implantation genetic diagnosis – a technique used to select embryos that have not inherited the mutation. However, there is no guarantee this technique will result in a successful pregnancy and funding for it on the NHS may not be available to all patients.