Radiation Therapy for Rhabdomyosarcoma
Radiation therapy uses high-energy radiation to kill cancer cells. It is often an effective way to kill cancer cells that can’t be removed with 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 removing the tumor completely 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).
Radiation isn’t 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 is causing.
This type of treatment is given by a doctor called a radiation oncologist. Before treatments start, the radiation team takes careful measurements with imaging tests such as MRI scans to determine the correct angles for aiming the beams and the proper dose of radiation.
Radiation is usually given daily (5 days a week) over many weeks. Each treatment is much like getting an x-ray, although the dose of radiation is much stronger. 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 spent making sure the radiation is aimed correctly. The actual treatment time each day is much shorter. Some younger children may be given medicine before each treatment to make them sleep so they won’t move during treatment.
Newer radiation techniques
Some newer techniques can help doctors aim the treatment at the tumor more accurately while reducing the radiation exposure to nearby healthy tissues. These techniques may help increase the success rate and reduce side effects. Most doctors now use 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 during each treatment so that the radiation can be aimed more accurately. 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 converge 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.
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 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, as well as a child’s age. Some effects are likely to last a short time, while others might have a longer lasting impact.
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. Radiation to the abdomen or pelvis can cause nausea, vomiting, and diarrhea. In some cases there may be damage to the bladder, which might cause urinary problems. 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. If it is needed, it is aimed very carefully to try to limit how much reaches the brain. Side effects of radiation therapy to the brain can include headaches and problems such as memory loss, personality changes, and trouble learning at school. These problems tend to become most serious 1 or 2 years after treatment.
Other long-term problems can include the formation of scar tissue and the slowing of bone growth in areas that get radiation. Depending on the child’s age and what parts of the body get the radiation, this could result in deformities or a failure to grow to full height. Radiation can also raise the risk of cancer many years later (see “ Possible late and long-term side effects of treatments”).
To limit the risk of serious long-term effects from radiation, doctors use the lowest dose of radiation therapy that is still effective.
For more on radiation therapy, see our document Understanding Radiation Therapy: A Guide for Patients and Families.
Last Medical Review: November 20, 2014 Last Revised: November 21, 2014