Radiation Therapy for Rhabdomyosarcoma

Radiation therapy uses high-energy waves or particles to kill cancer cells. It is a way to kill cancer cells that cannot be removed with surgery. When radiation therapy is used to help treat rhabdomyosarcoma (RMS), it is typically given with chemotherapy (chemo).

When might radiation therapy be used?

Radiation can be used when some of the cancer is left after surgery (clinical group II or III). It is not usually needed for people with embryonal fusion-negative RMS that can be removed completely by surgery (clinical group I).

Usually, radiation therapy is given to any RMS that remains after about 12 weeks of chemo. Radiation can be given right away, before chemo, if a tumor is causing blindness or is pressing on the spinal cord.

If the cancer has spread to another part of the body, radiation might be given to reduce any symptoms it is causing.

How radiation therapy is done

This type of treatment is given by a doctor called a radiation oncologist. Before treatments start, the radiation team must create a treatment plan. The team will take careful measurements with tests such as MRI scans during a session called a treatment simulation. The radiation field, or area where radiation will be given, and the dose will be defined based on these tests.

Radiation is usually given five days a week for 4-6 weeks. Each treatment is like getting an x-ray, although the dose of radiation is much stronger. For each session, the patient lies down on a special table while a machine gives the radiation. The treatment is not painful.

Each session lasts about 15 to 30 minutes. Most of the time for the treatment is spent making sure the radiation is aimed correctly. It is important that radiation is given to the exact field planned in the simulation. Patients may be fitted with a plastic mold that looks like a body cast to hold them in the same spot for each treatment. Younger children may be given medicine before each treatment to make them sleep so they will not move during treatment.

Types of radiation therapy

Modern radiation therapy techniques help doctors aim the treatment at the tumor more accurately than they could in the past.

Three-dimensional conformal radiation therapy (3D-CRT): 3D-CRT uses the results of imaging tests, such as MRI, and special computers to map the exact location of the tumor. Radiation beams are then shaped and aimed at the tumor from several directions. Each beam alone is fairly weak, which makes it less likely to damage normal body tissues, but the beams come together at the tumor to give a higher dose of radiation there.

Intensity-modulated radiation therapy (IMRT): IMRT is an advanced form of 3D therapy. Along with shaping the beams and aiming them at the tumor from several angles, the intensity (strength) of the beams is adjusted to limit the dose reaching the most sensitive normal tissues. This lets doctors deliver a higher dose to the cancer areas. Many major hospitals and cancer centers now use IMRT.

Proton beam radiation: Proton beam radiation uses radioactive particles that travel only a certain distance before releasing most of their energy. This type of radiation limits radiation exposure to normal healthy tissues.

Brachytherapy (internal radiation therapy): Another approach is to insert a radioactive source into or near the tumor for a short time. The radiation travels only a short distance, so the tumor gets most of the radiation. This may be useful in treating some bladder, prostate, vaginal, and head and neck area tumors. This type of radiation requires specialized doctors and may not be available in some cancer centers.

Intraoperative radiation therapy (IORT): In some centers, radiation may be given during surgery using a procedure called IORT. This uses one large dose of radiation given directly to the area of the tumor. This may be used in challenging cases where typical doses of radiation could not be safely given. The hope is that this approach may also reduce long-term side effects by giving lower doses of radiation.

The best approach to radiation treatment may differ based on specific RMS type, location, spread, whether the tumor was able to be removed with surgery, and the expertise and equipment available at your treatment center. Ask your care team about the plan for you or your child.

Possible side effects

Radiation therapy can be an important part of treatment. The side effects of radiation depend on where the radiation is given, the dose of radiation, and the person's age. Short-term effects of radiation occur during or shortly after treatment. Long-term effects can take months or years to develop.

Short-term side effects

• Fatigue
• Hair loss (in the area receiving radiation)
• Skin that may be red, tender, or dry similar to a sunburn (in the area receiving radiation)
• Low blood counts (this is more common if you are also getting chemo)
• Mouth sores, trouble swallowing and/or loss of appetite (from radiation to the head and neck area)
• Nausea, vomiting, cramps and/or diarrhea (from radiation to the abdomen or pelvis)
• Damage to the bladder, which might cause pain or problems when passing urine (from radiation to the abdomen or pelvis)

Long-term side effects

While radiation is an effective treatment for RMS, it has long-term side effects.

Radiation, especially in young children, can affect how bones and tissues grow. Children who have been treated with radiation should be watched closely as they age, since radiation could result in hormone changes or a failure to grow to full adult height. Radiation to an arm or leg may result in scarring that may lead to limb length differences or limited movement, which may need treatment.

Because radiation works by breaking DNA, it can increase the risk of a second cancer many years later. Depending on where radiation was given, early screenings for cancer may be recommended.

Many of the long-term effects of radiation are specific to where the radiation was given. For example, radiation given to the neck or jaw may affect the thyroid gland or teeth while radiation to the area around the eye can affect vision. It is best to speak with your radiation team about what specific long-term side effects you may need to watch for.

Radiation therapy for relapsed or recurrent RMS

If radiation therapy was not part of the initial treatment of RMS, it may be offered if the disease recurs. Radiation can also be used if a cancer has spread too much to be cured, but a tumor is causing symptoms like pain or trouble breathing. In these cases, short courses of radiation can be used to shrink the tumor and improve symptoms.