Radiation therapy for rhabdomyosarcoma

Radiation therapy uses high-energy rays or particles to destroy cancer cells. It is usually used to treat rhabdomyosarcoma (RMS). When planning the type and amount of radiation and when and how it is given, the healthcare team will consider:

• the age of your child
• the type of RMS
• where in the body the cancer started
• how much of the tumour remained after surgery
• whether there is cancer in nearby lymph nodes
• your child's personal needs

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 therapy)
• destroy cancer cells left behind after surgery to reduce the risk that the cancer will come back (recur) (called adjuvant therapy)
• relieve pain or control the symptoms of advanced RMS (called palliative 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 would affect how the child looks (their appearance) or how the affected area will work.

Radiation therapy is most often given after chemotherapy has started (after 6 to 12 weeks) and while chemotherapy is ongoing. The exact timing of radiation therapy depends on the location of the tumour. For example, if a tumour is in the tissue surrounding the brain and spinal cord (called the meninges) and has grown into the bones of the skull, the brain or spinal cord, radiation therapy and chemotherapy may be given early on and at the same time. Radiation therapy may be given later for RMS in other parts of the body. Radiation therapy is usually given 5 days a week for 5 to 6 weeks.

During external radiation therapy (also called external beam radiation therapy), a machine directs radiation through the skin to the tumour and some of the tissue around it.

The following types of external radiation therapy may be used to treat RMS.

3D conformal radiation therapy (3D-CRT) shapes the radiation beam to the tumour or treatment area. 3D-CRT uses CT or MRI images to create a precise 3D image of the tumour. The exact location and shape of the tumour is programmed into a computer and used to plan treatment. Several radiation beams are then shaped and aimed at the tumour from different directions to treat the tumour from all angles. The radiation beams are all the same strength. Each individual beam is fairly weak and less likely to damage normal tissues. A higher dose of radiation is delivered where the beams cross at the tumour.

Intensity-modulated radiation therapy (IMRT) is similar to 3D-CRT. It uses a special tool to shape and aim many radiation beams at the tumour from different angles. The strength (intensity) of the radiation beams can also be changed. 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 RMS in hard-to-reach areas such as the pelvis.

Stereotactic radiosurgery (SRS), also called 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. SRS may be used to treat RMS 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 who need 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 and then stop. As a result, protons cause less damage to nearby normal tissues. It is useful for treating tumours in hard-to-reach areas such as the spine or pelvis.

Internal radiation therapy places radioactive materials in the body. Larger doses of radiation can be given with internal radiation therapy than with external radiation therapy.

Brachytherapy is a type of internal radiation therapy. It uses a material called a radioactive isotope. It is placed right into the tumour or in the area where the tumour was removed. The radiation kills the cancer cells over time. Brachytherapy may be used to treat RMS in the bladder, vagina, prostate and head and neck.

Side effects can happen with any type of treatment for RMS, but every child's experience is different. Some children have many side effects. Other children have only a few side effects.

During 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. If your child develops side effects, they can happen any time during, immediately after or a few days or weeks after radiation therapy. Sometimes late side effects develop months or years 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 being treated, the specific area or organs being treated, the total dose of radiation and the child's age during treatment. Some common side effects of radiation therapy used for RMS are:

• fatigue
• low blood cell counts
• hair loss
• skin problems
• sore mouth and throat
• taste changes
• swallowing problems
• loss of appetite
• nausea and vomiting
• diarrhea
• bladder problems

Other side effects can develop months or years after treatment for RMS. Find out more about late effects of treatments for RMS.

Tell the healthcare team if your child has these side effects or others 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.