Radiation therapy for childhood bone cancer

Radiation therapy uses high-energy rays or particles to destroy cancer cells. It may be used to treat certain types of childhood bone cancer. It is used to treat childhood Ewing sarcoma. It is rarely used to treat childhood osteosarcoma. The healthcare team will plan the type and amount of radiation and when and how it is given.

Radiation therapy may be given:

• to shrink a tumour before surgery and make it easier to remove (called neoadjuvant therapy)
• to destroy cancer cells left behind after surgery or chemotherapy and reduce the risk that cancer will come back, or recur (called adjuvant therapy)
• as the main treatment, with chemotherapy, to destroy cancer cells
• to treat a recurrence
• to relieve pain or control the symptoms of advanced osteosarcoma (called palliative therapy)

Radiation therapy may be offered as the main treatment instead of surgery if doctors can't remove the tumour because it is large or it is near or touching vital structures such as the spinal cord.

The following types of radiation therapy are most commonly used to treat childhood bone cancer.

During external beam radiation therapy, a machine directs radiation through the skin to the tumour and some of the tissue around it. The radiation therapy team will base the size of the treatment area on the size of the tumour or tumours as well as a margin of healthy tissue surrounding the tumour.

Radiation therapy is usually given Monday to Friday in small daily doses (called fractions) over a period of 4 to 5 weeks.

Doctors may use the following types of external beam radiation therapy to accurately target the area to be treated and spare as much surrounding normal tissue as possible.

3D conformal radiation therapy (3D-CRT) involves many beams of radiation directed at the tumour. The radiation oncologist uses a CT scan or an MRI to map the exact location and shape of the tumour. The radiation beams are then shaped and aimed at the tumour from different directions to treat the tumour from all angles. Each individual beam is fairly weak and less likely to damage normal tissue. A higher dose of radiation is delivered where the beams meet at the tumour.

Intensity-modulated radiation therapy (IMRT) delivers radiation from many different angles to treat the entire tumour. In addition to shaping and aiming the radiation beams, IMRT allows the radiation oncologist to adjust the strength (intensity) of the individual beams. This reduces the dose of radiation reaching nearby normal tissues while allowing a higher dose to be delivered to the tumour. It is useful for treating tumours in hard-to-reach areas such as the spine or pelvis.

Stereotactic radiosurgery involves giving very high doses of radiation to a precisely defined area of the tumour over a small number of sessions. Stereotactic radiosurgery may be used in some treatment centres.

Conformal proton beam radiation therapy is a newer way of giving radiation that uses proton beams instead of x-ray beams. X-ray beams release energy before and after they hit their target. Protons only release energy after reaching a certain distance. As a result, protons cause less damage to tissues they pass through before reaching their target. Conformal proton beam radiation therapy causes the least amount of damage to nearby normal tissues. It is useful for treating tumours in hard-to-reach areas such as near the spinal cord or brain.

Conformal proton beam radiation therapy isn't available in Canada. Children who need this treatment must go to certain treatment centres in the US.

Side effects can happen with any type of treatment, but every child's experience is different. Some children have many side effects. Other children have few or none at all.

During external radiation therapy, the healthcare team protects healthy cells in the treatment area as much as possible. But damage to healthy cells can happen and may cause side effects. Side effects can happen any time during, immediately after or a few days or weeks after radiation therapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.

Side effects of external radiation therapy will depend mainly on the size of the area being treated, the specific area or organs being treated, the total dose of radiation, treatment schedule and the child's age. Some common side effects of radiation therapy used for childhood bone cancer are:

• fatigue
• skin problems
• hair loss
• bone marrow suppression
• nausea and vomiting
• loss of appetite
• diarrhea
• radiation enteritis

Some side effects can develop months or years after radiation therapy for childhood bone cancer. Find out more about late effects of treatment for childhood bone cancer.

Tell your child's healthcare team if your child has any side effects you think might be from radiation therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help your child deal with them.

Find out more about radiation therapy and side effects of radiation therapy. To make the decisions that are right for your child, ask the healthcare team questions about radiation therapy.