Causes, Risk Factors, and Prevention of Cancer in Children

Most childhood cancers are caused by DNA changes (mutations) that happen early in the child’s life, sometimes even before birth. Because of this, there are not many known risk factors or ways to prevent childhood cancers.

How changes in genes lead to cancer

The DNA changes that most often cause childhood cancer are acquired mutations. Every time a cell divides into 2 cells, it must make a copy of its DNA for the new cell. Acquired mutations happen because this process isn’t perfect, and errors sometimes occur, especially when the cells are growing quickly. This kind of gene mutation can happen at any time in life. Acquired mutations are only in the person’s cells and will not be passed on to their children.

Inherited genetic mutations (gene changes that are passed down by a parent) cause only a small number of childhood cancers.

Only certain mutations will cause a cell to become a cancer cell, and it typically takes several different gene mutations for cancer to form. To learn more, see Gene Changes and Cancer.

What increases the chance of a child getting cancer?

A risk factor is anything that increases the chances of getting a disease such as cancer. Different cancers have different risk factors. Since most childhood cancers are thought to be caused by random acquired mutations, there are not many known risk factors that increase the chance of a child getting cancer.

Factors that are believed to increase the risk of childhood cancer include:

• Radiation exposure
• Secondhand smoke
• Certain inherited syndromes

Most of the common risk factors for adult cancers (like using tobacco, alcohol, having high body fat, eating unhealthy foods, and not being physically active) take many years to increase cancer risk. Because of this, scientists don’t believe they are a cause of childhood cancers. Instead, childhood cancers are usually caused by random acquired mutations (gene changes).

Exposure to radiation

Children are more sensitive to radiation than adults, so it’s important to limit their exposure as much as possible. Although radiation exposure can cause childhood cancer, it’s more likely that exposure during childhood might raise their risk of cancer later in life.

Children might be exposed to radiation from:

• Environmental sources such as radon (common in basements) or building materials
• Medical imaging tests such as x-rays and CT scans
• Radiation therapy to treat cancer

Radiation exposure from imaging tests is a bigger concern for children than it is for adults. Although CT scans or x-rays might be needed, it’s important to use only as much radiation as necessary. Here are some things you can do to limit your child’s exposure:

• Keep track of your child’s imaging tests and discuss this history with the doctor any time a new test is recommended.

• Ask the doctor about the benefits and risks of the test being recommended.
• Ask the doctor if other tests that don’t use ionizing radiation, such as ultrasound or MRI, could be just as useful.       
• If an x-ray, CT scan, or other test that uses radiation is needed, ask the imaging facility about adjusting the dose for your child’s height and weight.

Although imaging tests use only a small amount of radiation, larger doses of radiation are used to treat cancer. Children who have had radiation therapy are at a higher risk for getting another cancer later. For example:

• Radiation to the head or brain can increase the risk of developing a benign (non-cancerous) or malignant (cancerous) brain tumor.
• Radiation to the head, neck, and spine can increase the risk of thyroid cancer.
• Radiation to the chest can increase the risk of lung and breast cancer later in life.
• Radiation to the abdomen, pelvis, or spine can increase the risk of colorectal cancer later in life. Experts recommend starting regular screening for colorectal cancer 5 years after radiation therapy or at age 30, whichever is later.

Because of this risk and other possible long-term effects, doctors try to avoid using radiation therapy in children or limit the doses used whenever possible. Even if a child needs radiation therapy, there are still ways to reduce their risk as much as possible. Talk to your doctor or cancer care team about limiting radiation exposure as much as possible. Make sure they have up-to-date information on your child’s height and weight for any tests or dose calculations.

Learn more about radiation exposure.

Exposure to tobacco smoke

Some studies suggest that exposing a child to secondhand smoke (SHS) during and after pregnancy might increase a child’s risk of certain cancers, however, more research is needed.

Family cancer syndromes

Family cancer syndromes are gene changes that are known to greatly increase a child’s, teen’s, or young adult’s risk for cancer. They also many be called inherited or genetic cancer syndromes.

Although having a family cancer syndrome increases the risk of cancer, most childhood cancers are not caused by inherited gene mutations. Only 8% to 9% of all cancers (including adult cancers) are strongly linked to inherited mutations.

Down syndrome

Children, teens or young adults with Down syndrome (trisomy 21) have an increased risk of developing leukemia (blood cancer) compared to children without Down syndrome.

Learn more about risk factors for childhood leukemia.

Can childhood cancers be prevented?

Not smoking during pregnancy may lower the risk of some cancers, as well as limiting your child’s exposure to radiation if possible. But since the causes of most childhood cancers are not known, most childhood cancers cannot be prevented.

If a child has a known gene mutation or family cancer syndrome that increases their risk of certain cancers, doctors might suggest certain cancer screening tests earlier or more often than most people. Depending on the type of mutation, they might suggest ways to prevent or reduce your risk of developing cancer.

If your child does develop cancer, it’s important to know that it’s extremely unlikely there is anything you or your child could have done to prevent it.

What can parents do to lower their child’s risk of cancer later in life?

Parents and caregivers have an important role in supporting their children’s long-term health, including reducing their risk of cancer later in life. By modeling and supporting a healthy lifestyle, you can instill habits that promote overall health and wellbeing. Here are some key ways you can support them:

• Not smoking is the number one way you can lower everyone’s risk of developing cancer. Smoking causes 1 in 5 cancers and 1 in 3 cancer deaths. It also increases the risk of many cancers, not just lung cancer.
• Getting to and maintaining a healthy weight is the 2^nd most important thing you can do to lower cancer risk. The best way to do this is to combine physical activity with a healthy eating pattern.
• Avoiding alcohol, which increases the risk of several cancers, is the 3^rd most important way to lower cancer risk. Any amount of alcohol increases the risk of several cancers.
• Vaccinating all children for human papillomavirus (HPV), which can increase their risk for several cancers. HPV causes almost all cervical cancers. It also causes other cancers such as mouth and throat cancer. HPV vaccines can prevent more than 90% of HPV-related cancers when given at the recommended ages.
• Protecting them from direct sunlight, the main source of ultraviolet (UV) radiation, which causes almost all skin cancers.

Minimizing exposure to carcinogens (things that are known or likely to cause cancer).

Preventing certain infections that increase cancer risk, such as HPV, Epstein-Barr virus (EBV, which causes mono), hepatitis B and C, and human immunodeficiency virus (HIV)

Learn more about Cancer Risk and Prevention.