Radiation therapy can be used to treat nearly any type of cancer in any part of the body, and is often most effective in treating solid tumors of the organs, as well as cancer of the bones, brain and blood. Patients of all ages, including children, can benefit from radiation therapy. Although radiation therapy can be given externally or internally, most pediatric cancers are treated with external-beam radiation.
External-beam radiation therapy can be used to slow tumor growth, prevent cancer from spreading or recurring, and relieve cancer symptoms. It is sometimes administered before surgery so that less tissue needs to be removed, or after surgery to destroy any cancerous cells that might remain. Certain cancers can be treated with radiation alone. The best type of treatment for a child depends on his or her individual condition.
Types of External-Beam-Radiation Treatment
External-beam radiation therapy (EBT) is designed to precisely deliver radiation energy to a tumor, usually during the course of several treatment sessions. EBT, which is painless, limits damage to surrounding healthy tissue.
Three-Dimensional Conformal Radiotherapy (3D-CRT)
Three-dimensional conformal radiotherapy is the most common external radiation treatment used for children. CT or MRI scans are performed to produce detailed, three-dimensional images of the area being targeted, which reduces the risk of irradiating healthy tissue around the tumor. As a result, 3D-CRT lowers the risk of complications and side effects from damage to healthy tissue and other organs.
Intensity-Modulated Radiation Therapy (IMRT)
Intensity-modulated radiation therapy precisely varies the radiation beam's intensity using computer guidance and special planning computers. It accurately directs the beam at a tumor, and the modulation of the beam allows different areas of the tumor to receive different doses of radiation as needed. IMRT is designed to increase the amount of radiation given to areas that need it, but reduce the amount of radiation exposure to surrounding normal tissue. The modulation of the beam's intensity and the precise placement of the beam make IMRT better than 3D-CRT at both directing the radiation dose at the tumor, and at protecting healthy tissue from the radiation.
Stereotactic Body Radiation Therapy (SBRT)
Stereotactic radiation therapy is designed to deliver, in often only a single treatment session, a large, precise dose of radiation to the tumor. Radiation beams are delivered from different angles and planes, which have been determined using three-dimensional imaging. Molds or frames designed to limit a patient's movements may be required. SBRT is used to treat only very small tumors or those located in hard-to-reach areas of the body.
Image-Guided Radiation Therapy (IGRT)
Image-guided radiation therapy uses frequent imaging during treatment to improve the precision and accuracy of the radiation beam. The machine used during treatment is equipped with imaging technology that allows the physician to see the tumor immediately before, or even as, radiation is directed at the tumor. Specialized computer software is then used to compare these images with ones taken before treatment, allowing adjustments to be made to the patient's position and/or placement of the radiation beam. As a result, the radiation directed at the tumor can be placed with great precision, minimizing damage to surrounding healthy tissue. IGRT is often used for cancers located in parts of the body that move, or that are near major organs and tissues that should not be irradiated.
Side Effects of Pediatric External-Beam-Radiation Treatment
External-beam radiation destroys malignant cells, but can also damage healthy ones, which is what causes side effects. The side effects a pediatric patient experiences depends on the part of the body being treated, and how large a dose of radiation is received. With proper treatment, most side effects can be controlled. Side effects may include:
- Fatigue
- Hair loss
- Sore mouth
- Tooth decay
- Gastrointestinal problems
- Skin damage/change near area being treated
- Low levels of white blood cells and platelets
Long-Term Risks of Pediatric External-Beam-Radiation Oncology
Although being exposed to radiation is problematic for both children and adults, certain factors make radiation exposure more dangerous for children. Children are more sensitive to radiation than adults and, because they have a greater number of years to live following treatment, there is more time for side effects from radiation to manifest themselves. Many side effects do not appear until many years after treatment. Long-term risks include:
Neurocognitive Problems/Brain Issues
Radiation to the brain may result in serious side effects approximately 1 or 2 years post-treatment. Headaches, memory loss, personality changes and learning difficulties have been reported.
Growth Slowdown
Radiation may slow the growth of certain areas of the body, and increase their risk for cancer. The bones, muscles and digestive tract are examples of susceptible areas.
Increased Cancer Risk
Chest radiation therapy may damage the lungs or heart, possibly raising the risk of lung or heart problems later in life. Radiation to the chest may also increase the risk of breast cancer, and, especially in smokers, lung cancer.
Fertility Problems
Radiation treatment can affect reproduction. Boys' sperm counts may diminish, and girls' ovaries may be affected. Radiation treatment seems to affect boys' fertility more than it does girls'.
In order to avoid these long-term side effects, doctors use radiation therapy for children only when absolutely necessary. If it is used, dosing is limited.