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We don’t know the cause of cancer in most cases. But we do know that some things, called risk factors, can increase your chances of developing cancer. About 1 in 4 cancers diagnosed in the UK (25%) could be avoided if people made changes to their lifestyles.
Some risk factors are very likely to cause cancer, whereas others will only slightly increase your likelihood of getting it. Having a particular risk factor for cancer, or being exposed to one, doesn’t mean that you will definitely get cancer - just as not having it doesn’t mean that you won’t.
Smoking| is a good example of this. If you smoke, it isn’t certain that you’ll get lung cancer| - just as if you don’t smoke, it’s not certain that you won’t. But smoking will greatly increase your risk of getting lung cancer. About 9 out of 10 people who develop lung cancer are smokers.
Cancer is very common, and nearly 1 in 3 of us will develop it at some time during our lives. This means that most of us have relatives who have had cancer.
Many people worry about getting cancer. Sometimes, people think they have a higher risk of developing it because there is a history of cancer in their family.
Fewer than 1 in 10 cases of cancer are associated with a family history of the disease.
Genes carry the biological information we inherit from our parents. They affect the way our bodies grow, work and look. Many people think that because they have one or two relatives with cancer, this means a cancer gene is present in their family. But this is not usually the case.
It’s only likely that a cancer gene is present in your family if:
If any of these apply to your family and you’re worried about your own risk of developing cancer, you may want to talk to your GP. If they think there’s a chance you may have an increased risk of developing cancer because of your family history, they will refer you to a genetic counsellor|, family cancer clinic or a cancer specialist.
If one middle-aged or elderly relative has had cancer, this does not necessarily mean there is a cancer gene in your family.
People with a strong family history of some cancers (bowel or breast cancers) are invited to have more regular screening| than people who don’t seem at increased risk.
Genetic testing| is usually available for breast, ovarian and bowel cancer, as well as for some other cancers, such as cancers of the endocrine glands|. Genetic testing is normally only possible if you have a relative with one of these cancers who is willing to be tested first.
Some cancer risk factors, such as age and family history, are beyond your control. But there are some risk factors you can control, known as lifestyle risk factors.
Here are some things you may want to consider:
Smoking| is the single biggest avoidable cause of cancer. In the UK more than a quarter of cancer deaths (about 29%) are caused by smoking. It is responsible for about 9 out of 10 cases of lung cancer (90%) and also plays a role in many other cancers, such as cancer of the mouth or throat|, bladder|, kidney|, pancreas|, bowel, stomach| and cervix|.
Breathing other people’s smoke (passive smoking) also increases your risk of developing cancer. If you smoke, giving up is the healthiest decision you can make.
Help is available if you want to give up smoking. Ask your GP for advice, or call the NHS smoking helpline|.
Lack of physical activity| can increase your risk of bowel cancer and may increase your risk of other types of cancer, including breast cancer. Evidence suggests that exercise regulates the level of hormones in the body, reducing your cancer risk. You don’t need to go to the gym - regular activity such as walking, cycling or swimming can be enough. If you’re not used to exercise, your GP can advise you on getting started.
Being overweight can increase your risk of developing cancer, particularly bowel, womb (uterus) and kidney cancer, and breast cancer after the menopause.
Being overweight changes the levels of hormones in your blood, and this may be how it increases your cancer risk.
We have more information on maintaining a healthy weight|.
There are often stories in the media about how diet| may affect your cancer risk. There is no single food or diet that can guarantee you won’t get cancer, just as there is no single food that can be blamed for causing it. But we do know that a healthy diet can reduce cancer risk, particularly the risk of developing bowel cancer.
A healthy diet is low in red meat, animal fat and salt, and includes plenty of fibre, fresh fruit and vegetables.
If you or your children are overweight, unsure about your diet or not used to exercise, mention your concerns to your GP. They can give you more information or help you get specialist support.
Get advice about eating healthily from our Macmillan dietitian, Helen.
Drinking more than the recommended amount of alcohol| increases your cancer risk, especially if you smoke. In particular, alcohol plays a role in mouth and throat cancer, but it can also increase your risk of bowel and breast cancer.
The European Code Against Cancer recommends that, to reduce cancer risk, men should drink no more than two units of alcohol a day and women no more than one unit a day. A unit is half a pint of ordinary strength beer, lager or cider, one small glass (125ml) of wine or a single measure (25ml) of spirits.
Spending some time outdoors in the sun helps you stay healthy, but it’s also important to protect your skin from burning as this can increase your risk of skin cancers.
Our bodies use the UVB rays in sunlight to make vitamin D, which is important for bone health and reduces the risk of many illnesses, including cancer. Most people can get enough exposure to UVB rays by going outside regularly, without sunscreen on, for a few minutes during the middle of the day. The amount of sun exposure you need depends on your hair and skin type. But it’s important not to stay out long enough to let your skin redden or burn.
If you are going to be out in the sun for longer than a few minutes, use a sun cream that protects against both UVA and UVB rays, with a sun protection factor (SPF) of at least 15. You should wear loose, cotton clothes that cover your body, as well as a hat. Take extra care with children.
Viruses| play a role in the development of certain cancers. Generally, these viruses are sexually transmitted, but some of them can also be transmitted through blood (for example, if drug users share a needle).
Human papillomavirus (HPV)| plays a role in many cases of cervical cancer, and it may also increase your risk of developing other cancers, such as somehead and neck cancers|, anal cancers| and cancers of the vulva| or penis|. Hepatitis B and C can increase the risk of liver cancer|, and the HIV (Aids) virus can increase the risk of developing lymphoma| and sarcoma|, although this is rare.
Practising safer sex by using condoms or other barrier methods of contraception and not sharing needles can help protect you from contracting these viruses.
Making these changes doesn’t mean that you definitely won’t get cancer - but they make it less likely and will improve your health generally.
This means knowing what is normal for you and what is a serious change.
You should see your GP if you have:
You are not wasting your doctor’s time if you mention any of these symptoms to them.
A common reaction to serious illness in the family, or to bereavement, is to feel more vulnerable to the same disease. If you can’t stop worrying, you may find it helpful to speak to a counsellor|. You can ask your GP for details of a local counselling service, or call our cancer support specialists|.
The mental health charity MIND has published a leaflet called How to Stop Worrying|.
If you’re worried about the occurrence of ovarian or breast cancer in your family and whether there might be an inherited genetic link, you can assess your risk using OPERA, our interactive program. OPERA (Online Personal Education and Risk Assessment) provides personalised information and support about your inherited risk of breast and ovarian cancer.
Please note that we do not intend this program to take the place of professional genetic counselling services. If you’re concerned about your genetic risk, you should consult your doctor.
Content last reviewed: 1 April 2011
Next planned review: 2013
For answers, support or just a chat, call the Macmillan Support Line free (Monday to Friday, 9am-8pm)
If you have any questions about cancer, need support or just want someone to talk to, ask Macmillan.
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© Macmillan Cancer Support 2013
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