The Late Effects of Radiation Therapy on Children

Advances in the treatment of pediatric cancer have resulted in an approximately 85% survival rate 5 years or more after cancer diagnosis. However, late effects from the cancer treatments can cause other health problems which develop years later.

Radiation therapy is a common treatment for cancer, which uses high-energy rays to kill cancer cells. Long-term side effects can show up months or years after treatment.       

Because of their developing bodies and long life expectancy after being treated with radiation, children require specific attention when radiation is used for treatment purposes.

The risks of radiation therapy can vary depending on the child’s age when they receive treatment. For this reason, we will look at children by age group to identify how they should be monitored to catch any late effects as early as possible.

Late Effects in Young Children Under 5 Years

Children under five years are especially vulnerable to radiation effects since their bodies are still growing and their organs are close together. When they receive radiation at this age, the impact on their development may occur in the following ways.

Growth issues: Bones can be damaged while they are still growing, and the radiation can cause them to grow more slowly or unevenly. This can result in defects in the way bones grow and their strength.

Brain development: Brain development is sometimes affected by radiation to the brain. This can lead to problems in learning to think, speak, and move as they get older. These delays are not always apparent at first but may appear as learning and memory problems as the child gets older.

Hearing Loss & Vision Problems: Including cataracts or dry eyes can occur, particularly after radiation for retinoblastoma or pituitary gland tumors.

Dental & Oral Problems: Radiation therapy to the head and neck can cause dental problems such as dry mouth, gum disease, cavities, or problems with tooth development.

Hormonal issues: Children who receive radiation to the head, brain, thyroid gland or their upper spine are at a higher risk of having hormone problems. These result from radiation damage in the brain, which is where the pituitary gland is located.

The pituitary gland is responsible for making hormones like growth hormone, sex hormones, and others. Younger children treated with radiation to these areas are more likely to have hormone problems. These can include low levels of the hormones produced by the pituitary gland, which may result in delayed puberty or challenges having children later on.  Children who have received this treatment will require monitoring for hormone, weight, and growth levels.

Additional Late Effects in Children Under 5 Years

• Increased Risk of Second Cancers: Children who are treated with radiation treatment at a young age have a higher chance of developing a second cancer later in their life.  The location of the secondary cancer is usually in the area of the body that received radiation before.
•  The risk of developing a second cancer is highest for the first 10 years after treatment, then decreases over time.
• Heart Problems: Radiation to the chest, lung, or breast area can cause heart issues, including heart failure or abnormal heart rhythms. These problems don’t usually show up until later in life.  It is important to tell all your doctors as an adult that you had radiation therapy as a child.
• Lung Issues: Radiation to the chest can damage lung tissue and lead to breathing problems at a later age.
• Emotional Distress & Mental Health: Children who are survivors of childhood cancer have a higher risk of developing depression and other mental health problems later in life.
•  Depression, anxiety, and other emotions can happen with any health issue and at any age. Often, children become more anxious about follow-up appointments and fear of recurrence as they get older. This anxiety can reach a serious level, so it’s important to make sure kids have someone they feel comfortable talking to about their feelings.

Late Effects in School-Age Children 5-12 years old

During this age, children experience rapid growth in their minds and bodies. They can still be affected by the late effects of radiation but somewhat differently than in younger children.

• Growth Issues: Radiation therapy can still affect bone growth and development in this age group, resulting in weaker bones or shorter stature. Socially, these problems make it more difficult to participate in sports or be physically active.
• Learning & Memory Problems: Radiation to the brain may cause memory and learning problems. Trouble concentrating, remembering things, or learning new information in school may also occur.
• Hormonal Changes: Altered hormonal functioning may cause delayed puberty and development. The need for hormone therapy to help balance their hormone levels may be considered.
• Heart & Lung Problems: Issues from radiation therapy may not appear during this age but may appear later in life.

Late Effects in Teens 13-18 years old

As children approach adulthood, late effects may become more visible in this age group. Teenagers are closer to adulthood, so the late effects of radiation therapy at this stage can have a big impact on their physical and emotional well-being.

• Growth and Puberty Issues: Teenagers who receive radiation to their bones might not reach their full height. Radiation can also affect puberty, leading to early or delayed sexual development. For example, it can damage the ovaries or testicles, which can cause infertility in the future. In some cases, radiation can also disrupt hormones that control growth, leading to problems with height and development.
• Learning and Memory Problems: Teenagers who had radiation to the brain may struggle with more complex thinking skills. They might have difficulty solving problems, planning, or remembering things, which can make school harder. These challenges can affect their ability to handle the responsibilities of adulthood.
• Endocrine Problems: Teenagers experience many hormonal changes during puberty. If radiation affects the glands that produce hormones, it can cause issues with metabolism, growth, and reproduction. Some teenagers might need lifelong hormone treatments to manage these changes.
• Emotional and Social Challenges: Teenagers care a lot about fitting in with their friends and peers. Radiation therapy can change their appearance or affect their abilities, which can lead to feelings of anxiety, depression, and isolation. These changes can also make it harder for them to participate in activities like sports, dating, or social events, which can negatively affect their emotional well-being.

Monitoring Children After Radiation Therapy

It is very important for children who have received radiation to continue to see their medical team for follow-up care to monitor their health afterward. They will need additional follow-up care to check for late effects, screening and tests to watch for any problems that may arise later, and monitoring their growth and development.

The medical follow-up will monitor for physical development, mental development such as memory, learning, and attention, as well as hormone levels, growth, and energy. Depending on the location of the radiation, X-rays, MRIs, EKG, etc. may be needed to check for possible problems in the bones, heart or lungs where the radiation was targeted.

What Childhood Cancer Survivors Can Do

Actions you can take to lower your risk for issues related to specific cancer treatment:

• There are ways you can lower your risk for bone problems related to cancer treatment, such as:
  • Weight-bearing activities like walking, running, or dancing.
  • Resistance activities like lifting weights, squats, or resistance bands.
  • Foods with calcium for bone health like dairy, eggs, leafy green vegetables, fortified cereal, or fatty fish)
  • Vitamin D to absorb calcium, from sunlight or a vitamin D supplement.
• Ask your doctor or cancer care team if you should get screened for osteoporosis or other bone problems based on your cancer history.
• Talk to them before taking any supplements, even if they’re over the counter.
• To avoid any potential hearing, vision or dental problems from radiation, make regular visits to the eye doctor.
• Have hearing tested to catch any issues early and get hearing aids or glasses if needed. Regular dentist visits for check-ups and cleanings, and good care of your teeth is important.
• Follow a heart-healthy diet with regular exercise, avoid alcohol, tobacco and other inhalants.
• Manage stress to lower your risk for heart problems.
• If you have the type of cancer treatment that can cause lung issues, ask your doctor if you should see a lung doctor or have special lung testing done.  If you ever need general anesthesia, tell the doctor about any radiation treatment that may have caused lung problems.
• Use sunscreen daily, all year.
• Regular follow-ups with your doctor are essential to catch any late effects as early as possible. Make sure your doctor knows about your cancer and the treatments you have received.
• Talk with your doctor about the cancer screenings you should get, how often to get them, and when to have them done.  Take an active part in your care!

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References

Government of Canada, Canadian Nuclear Safety Commission, May 16, 2024

Kutanzi KR, Lumen A, Koturbash I, Miousse IR. Pediatric Exposures to Ionizing Radiation: Carcinogenic Considerations. International Journal of Environmental Research and Public Health. 2016 Oct 28.

American Cancer Society, “Late and Long-Term Effects of Childhood Cancer Treatment” February 3, 2025