Radiation therapy for rhabdomyosarcoma

Radiation therapy (radiotherapy) uses high-energy radiation to kill cancer cells. It is often an effective way to kill cancer cells that cannot be removed during surgery. When radiation therapy is used to help treat rhabdomyosarcoma (RMS), it is typically given along with chemotherapy.

Radiotherapy is most useful if some of the main tumor is still left after surgery (group II or III) or if completely removing the tumor would mean loss of an important organ, like the eye or bladder, or would be disfiguring. It is not usually needed for children with embryonal rhabdomyosarcoma (ERMS) that can be completely removed by surgery (group I).

Usually radiation therapy is given to any area of remaining disease after 6 to 12 weeks of chemotherapy. An exception is when a tumor near the meninges (linings of the brain) has grown into the skull bones, into the brain itself, or into the spinal cord. In these patients radiation therapy is started right away (along with chemotherapy).

Radiotherapy cannot be given to the whole body to treat metastases, but it can be given to certain areas of known disease to reduce any symptoms the cancer may be causing.

Radiation therapy is much like getting an x-ray, although the dose of radiation is much higher. Radiation is usually given daily (5 days a week) over many weeks. 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.

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 session lasts about 15 to 30 minutes, with most of the time being spent making sure the radiation is aimed correctly. The actual treatment time each day is much shorter. Some younger children may be given medicine to make them drowsy before each treatment.

Newer radiation techniques

Some newer techniques may help doctors to more accurately aim treatment at the tumor while reducing the radiation exposure to nearby healthy tissues. These techniques may help increase the success rate and reduce side effects. Many doctors now recommend using these approaches when they are available.

Three-dimensional conformal radiation therapy (3D-CRT): 3D-CRT uses special computers to precisely map the location of the tumor. Depending on where the tumor is, your child may be fitted with a plastic mold resembling a body cast to keep him or her in the same position so that the radiation can be aimed more accurately. Radiation beams are then shaped and aimed at the tumor from several directions, which makes the radiation less likely to damage nearby normal tissues.

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

Brachytherapy (internal radiation therapy): Another newer approach is to insert a radioactive pellet into or near the tumor. The radiation from the pellet travels only a short distance, so the tumor gets most of the radiation. This approach may be especially useful in treating some bladder, vaginal, and head and neck area tumors. Some early studies suggest that this may be a good way to preserve the function of these organs in many children.

Other newer techniques, such as stereotactic radiotherapy and proton beam radiotherapy, are discussed briefly in the section, "What's new in rhabdomyosarcoma research and treatment?"

Possible side effects

The side effects of radiation therapy depend on the dose of radiation and where it is aimed.

Short-term side effects can include fatigue and increased numbers of infections. Effects on skin areas that receive radiation can range from hair loss and mild sunburn-like changes to more severe skin reactions. If the abdomen or pelvis gets radiation, nausea, vomiting, and diarrhea are common. In some cases there may be damage to the bladder or bowel. Radiation to the head and neck can cause mouth sores and loss of appetite.

Small children's brains are very sensitive to radiation, so doctors try to avoid using radiation to the head whenever possible. Side effects of brain radiation therapy usually become most serious 1 or 2 years after treatment and may include headaches and problems such as memory loss, personality changes, and trouble learning at school.

Other long-term problems can include scar tissue formation and the slowing of bone growth. Depending on the age of the child and what parts of the body get the radiation, this could result in deformities or a lack of growth to full height. Radiotherapy may also raise the risk of cancer many years later in the areas that got radiation (see "Possible long-term side effects of treatments").

To lower the risk of serious long-term effects from radiation, doctors use the lowest dose of radiation therapy that is still effective.

For more detailed information on radiation therapy, see our document, Understanding Radiation Therapy: A Guide for Patients and Families.