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Radiation therapy uses high-energy rays or particles to kill cancer cells.

When might radiation therapy be used?

Radiation therapy is sometimes a necessary part of treatment, but because of the possible long-term side effects in young children, doctors avoid using it when possible.

Most children with neuroblastoma will not need radiation therapy. It is most commonly used in children with high-risk neuroblastoma, typically after a stem cell transplant. It might also be used for children with low- and intermediate-risk neuroblastoma, if a child has life-threatening symptoms and needs emergency treatment to shrink the tumor.

How is radiation therapy given?

Two types of radiation therapy can be used to treat children with neuroblastoma:

• External beam radiation therapy
• MIBG radiotherapy

External beam radiation therapy

External radiation therapy uses a machine to focus a beam of radiation on the cancer from a radiation source outside the body. This type of treatment might be used:

• To try to shrink tumors before surgery, making them easier to remove
• To treat larger tumors that are causing serious problems (such as trouble breathing) and do not respond quickly to chemotherapy
• As part of the treatment regimen after a stem cell transplant in children with high-risk neuroblastoma to destroy neuroblastoma cells that remain behind. Radiation might be given to the primary tumor area and other areas of the body that might have active disease seen on an MIBG scan.
• To help relieve pain caused by advanced neuroblastoma

When radiation is aimed at the whole body, it is known as total body irradiation (TBI). This was used in the past for children with high-risk neuroblastoma before a stem cell transplant, but now it's more common for radiation only to be given after a stem cell transplant, and only to the primary tumor site and any other areas of the body that might have active neuroblastoma cells.

Before the 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.

Your child might also be fitted with a plastic mold resembling a body cast to keep them in the same position during each treatment so that the radiation can be aimed more accurately.

The number of radiation treatments given depends on the situation.

For each treatment session, your child lies on a special table while a machine delivers the radiation from a precise angle. Radiation therapy is much like getting an x-ray, but the dose of radiation is much higher. The treatment is not painful. Each actual treatment lasts only a few minutes, but the setup time – getting your child into place for treatment – usually takes longer. Young children may be given medicine to make them sleep so they will not move during the treatment.

Possible side effects of external radiation therapy

Radiation therapy is sometimes an important part of treatment, but young children’s bodies are very sensitive to it, so doctors try to use as little radiation as possible to help avoid or limit any problems. Radiation can cause both short-term and long-term side effects, which depend on the dose of radiation and where it is aimed.

Short-term effects

• Radiation can affect the skin in the area treated. Effects can range from mild sunburn-like changes and hair loss to more severe skin reactions.
• Radiation to the abdomen (belly) can cause nausea or diarrhea.
• Radiation therapy can make a child tired, especially toward the end of treatment.

Radiation can also make the side effects of chemotherapy worse. Talk with your child’s doctor about the possible side effects because there are ways to relieve some of them.

Long-term effects

• Radiation therapy can slow the growth of normal body tissues (such as bones) that get radiation, especially in younger children. In the past this led to problems such as short bones or a curving of the spine, but this is less likely with the lower doses of radiation used today.
• Radiation can affect the thyroid gland in the neck, causing it to make less thyroid hormone (hypothyroidism). Symptoms of hypothyroidism can vary greatly. In children, hypothyroidism can affect growth and development. Thyroid replacement medicine is usually all that's needed to manage hypothyroidism.
• Radiation that reaches the chest area can affect the heart and lungs. This does not usually cause problems right away, but in some children it may eventually lead to heart or lung problems as they get older.
• Radiation to the abdomen in girls can damage the ovaries. This might lead to abnormal menstrual cycles or problems getting pregnant or having children later on.
• Radiation can damage the DNA inside cells. As a result, radiation therapy slightly increases the risk of developing a second cancer in the areas that get radiation, usually many years after the radiation is given.

Close follow-up with doctors is important as children grow older so that any problems can be found and treated as soon as possible. For more on the possible long-term effects of treatment, see Late and Long-term Effects of Neuroblastoma and Its Treatment.

MIBG radiotherapy

As described in Tests for Neuroblastoma, MIBG is a chemical similar to norepinephrine, which is made by sympathetic nerve cells. A slightly radioactive form of MIBG is sometimes injected into the blood as part of an imaging test to look for neuroblastoma cells in the body. This is called an MIBG scan.

A more highly radioactive form of MIBG can also be used to treat some children with advanced neuroblastoma, often along with other treatments. Once injected into the blood, the MIBG goes to neuroblastoma cells anywhere in the body and delivers its radiation. (This type of radiation travels only a very short distance, so it doesn’t affect most healthy cells in the body.)

The child will need to stay in a special hospital room for a few days after the injection until most of the radiation has left the body. Most of the radiation leaves the body in the urine, so younger children might need to have a catheter in the bladder to help urine leave the body, usually for a couple of days.

Possible side effects

Most of the radiation from MIBG therapy stays in the area of the neuroblastoma, so most children don't have serious side effects from this treatment. MIBG therapy can sometimes cause mild nausea and vomiting. It can also make some children feel tired or sluggish. Some children might have swollen cheeks from the MIBG treatment because it can affect the salivary glands. Rarely, it might cause high blood pressure for a short period of time.