Radiation Therapy for Brain Tumors in Children

Radiation therapy uses high-energy x-rays or small particles to kill cancer cells. This type of treatment is given by a doctor called a radiation oncologist.

When might radiation therapy be used?

Radiation therapy may be used in different situations for brain or spinal cord tumors:

• After surgery to try to kill any remaining tumor cells
• As part of the main treatment if surgery is not a good option
• To help prevent or relieve symptoms from the tumor

Children younger than 3 years are usually not given radiation because of long-term side effects on brain development. Instead, they are treated mainly with surgery and chemotherapy. In some cases, this approach may cure the cancer and radiation may not be needed. In other cases, radiation may still be needed but doctors hope to delay it until the child is older.

Radiation can also cause some problems in older children and teens. Radiation oncologists try very hard to deliver enough radiation to the tumor while limiting radiation to normal surrounding brain areas as much as possible.

External beam radiation therapy

External beam radiation therapy (EBRT) is the most common kind of radiation therapy used to treat brain tumors. Radiation is focused on the tumor from a source outside the body.

Before radiation treatments start, the radiation team will take careful measurements with imaging tests, such as MRI scans, to determine the correct angles for aiming the radiation beams and the proper dose of radiation. This planning session is called a simulation.

Your child or teen might be fitted with a plastic mold like a body cast to keep them in the same position so the radiation can be aimed more accurately.

Each treatment session is given while lying on a special table while a machine delivers the radiation from precise angles. Radiation therapy is like getting an x-ray, but the dose of radiation is much higher. Treatment is not painful. Each session only lasts about 15 to 30 minutes, but most of the time is spent making sure the radiation is aimed correctly. The actual treatment time each day is much shorter. Young children might be given medicine to make them sleep so they will not move during the treatment.

The number of radiation treatments given depends on the situation.

Radiation therapy can damage normal brain tissue, so doctors try to deliver high doses of radiation to the tumor with the lowest possible dose to normal surrounding brain areas. Several techniques can help doctors focus the radiation more precisely:

Brachytherapy (internal radiation therapy)

In brachytherapy, radioactive material is inserted directly into or near the tumor. This can be done during surgery to remove the brain tumor, or it might be an option if the tumor comes back after treatment. This type of radiation may be an option for glioblastomas or high-grade gliomas that come back after treatment.

The radiation from brachytherapy travels only a short distance, so the tumor gets most of the radiation. This treatment requires specialized doctors and may not be available in all cancer centers. This type of radiation is not used often for children and adolescents.

Possible effects of radiation therapy

Radiation is more harmful to tumor cells than it is to normal cells. Still, radiation can also damage normal brain tissue, especially in children younger than 3 years, which can lead to side effects.

Short-term side effects

Short term side effects during or after radiation treatments can include:

• Fatigue
• Hair loss (in the area receiving radiation)
• Skin that may be red, tender, or dry (similar to a sunburn) in the area receiving radiation
• Low blood counts (this is more common when also getting chemo)
• Mouth sores, trouble swallowing, and/or loss of appetite (from radiation to the head and neck area)
• Nausea and vomiting
• Headaches

Some weeks after radiation therapy, children may become drowsy or have other nervous system symptoms like irritability. This is called radiation somnolence syndrome. It usually passes after a few weeks.

Long-term side effects after treatment

While radiation is an effective treatment for brain tumors, it has long-term side effects.

Talk to your cancer care team about which specific long-term side effects you may need to watch for.

Balancing the risks and benefits

The risk of all of these side effects must be balanced against the risks of not using radiation and having less control of the tumor. If problems are seen after treatment, it is often hard to know whether they were caused by damage from the tumor itself, from surgery or radiation therapy, or from some combination of these. Doctors are constantly testing lower doses or different ways of giving radiation to see whether they can be effective while causing fewer problems.

Normal brain cells grow quickly in the first few years of life, making them very sensitive to radiation. Because of this, radiation therapy is often not used or is postponed in children younger than 3 years old to avoid damage that might affect brain development. This needs to be balanced with the risk of tumor regrowth, because early radiation therapy may be lifesaving in some cases. It is important to talk with your cancer care team about the risks and benefits of treatment.