Radiation therapy (radiotherapy) uses high-energy radiation to kill cancer cells. It is an effective way to kill cancer cells that cannot be removed during surgery.

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 rhabdomyosarcomas 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.

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 over many weeks. 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.

Possible side effects

The short-term side effects of radiation therapy in children can include fatigue and increased numbers of infections. Effects on skin areas that receive radiation can range from mild sunburn-like changes to more severe skin reactions. If the abdomen gets radiation, nausea, vomiting, and diarrhea are common. If the head and neck are included, mouth sores and loss of appetite are common.

Small children's brains are very sensitive to radiation, so doctors try to avoid using radiation to the head whenever possible. Other long-term problems can include scar tissue formation and the slowing of bone growth. Depending on 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 below).

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

Newer radiation techniques

Several newer techniques may allow doctors to more accurately aim treatment at the tumor while reducing the radiation exposure to nearby healthy tissues. These techniques may offer better chances of increasing the success rate and reducing 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 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 allows doctors to deliver an even higher dose to the cancer areas. Many major hospitals and cancer centers are now able to provide IMRT.

Brachytherapy: 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 damage. This approach is 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?"

For more detailed information on radiation therapy, see the separate American Cancer Society document, Understanding Radiation Therapy: a Guide for Patients and Families.

Last Medical Review: 09/08/2009
Last Revised: 09/08/2009