Radiation therapy for rhabdomyosarcoma
Radiation therapy uses high-energy rays or particles to destroy cancer cells. Radiation therapy is often used to treat rhabdomyosarcoma. The healthcare team will consider your child’s personal needs to plan the type and amount of radiation and when and how it is given. Your child may also receive other treatments.
Radiation therapy is given for different reasons. Your child may have radiation therapy:
- to shrink a tumour before surgery so it is easier to remove (called neoadjuvant radiation therapy)
- to treat cancer that is left after surgery
- instead of surgery
- to relieve pain or control the symptoms of advanced rhabdomyosarcoma (called palliative radiation therapy)
Radiation therapy may be given after surgery if cancer cells are found in the healthy tissue removed along with the tumour (called positive surgical margins). It is often used after or instead of surgery if surgery to completely remove the tumour would affect how the child looks or how the affected area will work after surgery.
Radiation therapy is most often given after chemotherapy has begun, but while it is ongoing. The exact timing of radiation therapy depends on the location of the tumour. For example, if a tumour is in the layers of connective tissue that cover the brain and spinal cord (called the meninges) and has grown into the bones of the skull, the brain or the spinal cord, radiation therapy and chemotherapy may be given early on, in the same time period, whereas radiation is often given later for rhabdomyosarcoma in other sites. Children whose tumours are of the less favourable alveolar histology usually receive radiation even if the tumour has been entirely removed.
External beam radiation therapy
During external beam radiation therapy, a machine directs radiation through the skin to the tumour and some of the tissue around it. The size of the area treated and the dose of radiation used depend on the size of the tumour, if the tumour has grown into surrounding tissue and if the cancer has spread.
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.
3-D conformal radiation therapy (3D-CRT) delivers radiation to the tumour from different directions. The radiation oncologist uses MRI images to map the exact location and shape of the tumour. Several 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 tissues. A higher dose of radiation is delivered to the tumour, where the beams meet.
Intensity-modulated radiation therapy (IMRT) is similar to 3D-CRT in that it 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, or intensity, of the individual beams. This allows a higher dose to be delivered to the tumour and reduces the dose of radiation reaching nearby normal tissues. IMRT can be useful for treating rhabdomyosarcoma in hard-to-reach areas such as the pelvis.
Stereotactic radiation therapy uses a rigid frame attached to the skull to give radiation to a very specific area of the brain. It is usually given as many low doses of radiation over a period of time. Stereotactic radiation therapy may be used to treat rhabdomyosarcoma in the head or neck.
Conformal proton beam radiation therapy is a new way of giving radiation. It isn’t available in many treatment centres. Currently, there are no machines in Canada. Children requiring this treatment have to go to certain centres in the US. Conformal proton beam radiation therapy 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 the spine or pelvis.
Side effects can happen with any type of treatment for rhabdomyosarcoma, but every child’s experience is different. Some children have many side effects. Other children have few or none at all.
During radiation therapy, the healthcare team protects healthy cells in the treatment area as much as possible. But damage to these 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 radiation therapy will depend mainly on the size of the area treated, the specific area or organs treated, the total dose of radiation and the child’s age during treatment. Some common side effects of radiation therapy used for rhabdomyosarcoma are:
- low blood cell counts (bone marrow suppression)
- hair loss
- skin reactions
- sore throat
- taste changes
- difficulty swallowing
- loss of appetite
- nausea and vomiting
Other side effects can develop months or years after treatment for rhabdomyosarcoma. Find out more about late effects of treatments for rhabdomyosarcoma.
Tell the 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.