Radiation therapy for neuroblastoma

Radiation therapy uses high-energy rays or particles to kill cancer cells. Radiation is sometimes a necessary part of treatment, but because of the possible long-term side effects in children, it is avoided when possible. Two types of radiation therapy can be used to treat children with neuroblastoma.

External beam radiation therapy

External radiation therapy focuses the radiation on the cancer from a source outside the body. This type of treatment might be used:

• To destroy neuroblastoma cells that remain behind after surgery and chemotherapy
• To try to shrink tumors before surgery, making them easier to remove at the time of surgery
• 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 (along with high-dose chemotherapy) before a stem cell transplant in children with high-risk neuroblastoma
• To help relieve pain caused by advanced neuroblastoma

Most often, the radiation is aimed at the tumor itself, but in some cases it may also target other parts of the body to reduce the risk of cancer spread. When radiation is aimed at the whole body, it is known as total body irradiation (TBI).

Before treatments start, the radiation team takes 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.

Radiation therapy is much like getting an x-ray, but the dose of radiation is much higher. Your child may be fitted with a plastic mold resembling a body cast to keep him or her in the same position each time so that the radiation can be aimed more accurately. For each session, your child will lie on a special table while a machine delivers the radiation from a precise angle. 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. The number of radiation treatments given will depend on the situation.

Possible side effects: Radiation 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 therapy can cause both short-term and long-term side effects, which depend on the dose of radiation and where it is aimed.

Possible short-term effects:

• Effects on skin areas that receive radiation 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 may 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.

Possible 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 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 may damage the ovaries. This might lead to abnormal menstrual cycles or problems getting pregnant or having children later on.
• Radiation can damage DNA. 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 the section “Long-term effects of neuroblastoma and its treatment.”

MIBG radiotherapy

As described in the section “How is neuroblastoma diagnosed?,” 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 bloodstream as part of an imaging test to look for neuroblastoma cells in the body.

A more highly radioactive form of MIBG is also used to treat some children with advanced neuroblastoma, often along with other treatments. Once injected into the bloodstream, the MIBG goes to the sites of tumors anywhere in the body, where it delivers its radiation. The child will need to stay in a special room for a few days after the injection until most of the radiation has left the body.

Possible side effects: MIBG therapy can sometimes cause nausea and vomiting. It can also lower blood cell counts because of its effects on the bone marrow. In rare cases it may cause high blood pressure for a short period of time. Because it contains iodine, MIBG may build up in the thyroid gland, which can sometimes lower the levels of thyroid hormone in the body.