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.

Although we have identified a number of lifestyle changes that can help to reduce the risk of adults developing cancer. 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:

  • medical conditions
  • problems with development in the womb
  • exposure to infections
  • exposure to radiation
  • previous cancer treatments

Medical conditions

Certain conditions can increase a child's risk of developing some types of cancers.

For example, children with Down's syndrome are 10 to 20 times more likely to get leukaemia Open a glossary item than other children. Leukaemia is still very rare, even in children with Down’s syndrome.


Retinoblastoma is a rare type of eye cancer. Some children are born with a change (mutation) in the retinoblastoma gene Open a glossary item, 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 (40%) have the inheritable type of retinoblastoma. This often affects both eyes (bilateral).

Some other childhood cancers, such as Wilms’ tumour (kidney cancer in children), may have a genetic link. But the link isn’t as clear as with retinoblastoma.

Problems with development in the womb

Some childhood cancers such as Wilm’s tumours and retinoblastomas begin when the baby is still inside their mother.

When a baby is growing in the womb Open a glossary item, 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. While glandular fever can be very unpleasant, it usually passes within a few weeks and 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 such as Hodgkin lymphoma and Burkitt’s lymphoma.

Most people get infected with EBV as a child and stay infected for life without ever experiencing any symptoms. Because of how common it is, there is nothing you can do to prevent you, or your child, coming into contact with EBV at the moment.

Exposure to radiation

Cancer treatment can also include radiotherapy. It uses a type of radiation called ionising radiation. Children who have radiotherapy for cancer have a slightly greater risk of developing another type of cancer later on. But the risk is small compared to the risk to their health if the original cancer was not treated with radiotherapy.

Radon gas is a natural radioactive gas and it is a type of ionising radiation. It is found 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 such as acute leukaemia. But this is often many years later in children and adults.

Last reviewed: 
22 Oct 2020
Next review due: 
22 Oct 2023
  • Children's cancer statistics: Cancer Research UK (Cancer Stats)
    Accessed October 2020

  • Inherited genetic susceptibility to acute lymphoblastic leukemia in Down Syndrome
    A L Brown and others
    Blood, 2019. Volume 134, Issue 15, Pages 1227 to 1237

  • Retinoblastoma
    I Aerts and others
    Orphanet Journal of Rare Diseases, 2006. Volume 1, Article number 31

  • Epidemiology of Childhood Cancer
    J Little
    Lyon: IARC press, 1999

  • International Agency for Research on Cancer. List of classifications by cancer sites with sufficient or limited evidence in humans, Volumes 1 to 127
    Accessed October 2020

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. If you need additional references for this information please contact patientinformation@cancer.org.uk with details of the particular risk or cause you are interested in.

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