Risks and causes of cancer in children
What are risk factors?
Anything that increases your risk of getting cancer is a risk factor. Having a risk factor does not mean you will get cancer.
Do we know what causes children's cancers?
We don’t know what causes, or how to prevent most childhood cancers. The risk factors for children’s cancer aren’t well understood. This is because these cancers are rare and there are many different types. This makes researching these cancers difficult.
Parents of children with cancer can sometimes feel like something they did, or didn’t do, caused their child’s cancer. We don’t know what causes, or how to prevent most childhood cancers and no one should feel blamed.
We have identified a number of lifestyle changes that can help to reduce the risk of adults developing cancer. However it doesn’t look like there is anything we can do to prevent most childhood cancers.
Cancer is not infectious. You can’t catch it from another person. And your child can’t pass it on to their siblings or other children in their school. It is unlikely for 2 children in one family to get diagnosed with childhood cancer.
Risk factors for children’s cancers are not well understood. This is because this group of cancers are rare and there are lots of different types. This makes them difficult for researchers to study.
There are some known risk factors that can increase the risk of a child developing cancer. The list below gives some examples.
It is important to note that most children with cancer aren’t affected by any of them. And many children who are affected by these risk factors won't go on to develop cancer.
Known risk factors
These include:
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medical conditions
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genetics
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problems with development in the womb
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exposure to infections
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exposure to radiation
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previous cancer treatments
Medical conditions
Certain conditions can increase a child's risk of developing some types of cancers.
An example is children with Down's syndrome. They are 10 to 20 times more likely to get 
than other children. Leukaemia is still very rare, even in children with Down’s syndrome.
Genetics
Retinoblastoma is a rare type of eye cancer. Some children are born with a change (mutation) in the retinoblastoma , also known as the RB1 gene. This may be because they inherited the gene from one of their parents. Or because a change happened to this gene during the very early stages of its development in the womb. Most children who have a change to the RB1 gene develop retinoblastoma. About 40 out of 100 children diagnosed (about 40%) have the inheritable type of retinoblastoma. This often affects both eyes (bilateral).
Some other childhood cancers, such as Wilms tumour may have a genetic link. But the link isn’t as clear as with retinoblastoma.
Certain genetic conditions can increase a child's risk of developing some types of brain tumours. But this is very rare. And not every child with these conditions develops a brain tumour.
Some other genetic conditions associated with different childhood cancer types include:
Neurofibromatosis type 1 and type 2 (NF1 or NF2) Li-Fraumeni syndrome Familial adenomatous polyposis - DICER1 syndrome
Gorlin syndrome (also known as Nevoid basal cell carcinoma syndrome)
Problems with development in the womb
Some childhood cancers begin when the baby is still inside their mother. For example Wilms tumour and retinoblastomas.
When a baby is growing in the , many parts of the body, such as the kidneys and eyes, develop very early on. Sometimes something goes wrong. And some of the cells that should have turned into developed (mature) cells to form a part of the body don’t. Instead they remain as very early (immature) cells.
Usually, these immature cells don't cause any problems and mature by themselves by the time the child is 3 or 4 years old. But if they don’t, they may begin to grow out of control and develop into a cancerous tumour.
Exposure to infections
Epstein Barr virus (EBV) is a common infection in young children. It usually causes no symptoms. But, it can cause glandular fever (infectious mononucleosis) in teenagers and young adults. Glandular fever can be very unpleasant and it usually passes within a few weeks. But it doesn’t mean that you go on to develop cancer. Once infected, a person remains a carrier of EBV for life, but the virus normally doesn’t cause any symptoms at all.
In rare cases, infection with EBV can contribute to the development of cancers. These include Hodgkin lymphoma and Burkitt’s lymphoma.
Most people get infected with EBV as a child and stay infected for life without ever having any symptoms. Because of how common EBV is, at the moment you can't do anything to prevent you or your child from getting it.
Exposure to radiation
Cancer treatment for children can also include radiotherapy. It uses a type of radiation called ionising radiation. This means they have a slightly higher risk of developing another type of cancer later on. But the risk is small compared to the risk to their health if the cancer was not treated with radiotherapy.
Radon gas is a natural radioactive gas and it is a type of ionising radiation. You find it in the air at a low level outdoors, but it can sometimes build up to high concentrations indoors. Because it is a natural gas, it is difficult for us to control our exposure to it. Overall, studies so far have only suggested that there might be a weak link between indoor levels of radon gas and risk of childhood leukaemia.
Previous cancer treatments
Past treatment with chemotherapy can increase the risk of cancers. These include acute leukaemia. But this is often many years later in children and adults.
