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Radiation therapy uses high-energy rays or particles to kill cancer cells. It is a way to kill cancer cells that cannot be removed with surgery.

When is radiation therapy used?

Ewing sarcomas are very sensitive to radiation, so radiation therapy can sometimes be helpful in treating them.

Radiation therapy might be used in different situations:

• After surgery if it’s not clear that all of the cancer was removed. For example, if cancer cells were found in the edges (margins) of the removed tissue. This is done to try to kill any cancer cells that may have been left behind.
• Instead of surgery (possibly along with other treatments) for bone cancers that can’t be removed (resected) completely. Radiation can slow tumor growth and control symptoms like pain and swelling.
• When the cancer comes back, to treat symptoms and slow regrowth of the cancer.

How radiation therapy is given

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 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 5 days a week for several weeks. Each treatment is like getting an x-ray, but the dose of radiation is much stronger. For each session, a person will lie on a special table while a machine gives the radiation from precise angles. The treatments are not painful.

Each session lasts about 15 to 30 minutes. Most of the time for the treatment is spent making sure that the radiation is aimed correctly. It is important that radiation is given to the exact field planned in the simulation.  You (your child) may be fitted with a plastic mold that looks like a body cast to hold you (your child) in the same spot for each treatment. Some younger children may be given medicine before each treatment to make them sleep so they won’t move during the session.

Types of radiation therapy

Modern radiation therapy techniques help doctors aim the treatment at the tumor more accurately than they could in the past. The best approach to radiation treatment may be different for everyone and depends on the expertise and equipment available at your treatment center. Ask your cancer care team about the plan for you (your child).

Three-dimensional conformal radiation therapy (3D-CRT)

3D-CRT uses the results of imaging tests (such as MRI) and special computers to precisely map the location of the tumor. Several radiation beams are then shaped and aimed at the tumor from different directions. Each beam by itself is fairly weak, which makes it less likely to damage normal body tissues, but the beams combine at the tumor to give a higher dose of radiation there.

Intensity modulated radiation therapy (IMRT)

IMRT is an advanced form of 3D therapy that can be especially useful for tumors with complex shapes or tumors near important structures, such as the spine. 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 the doctor deliver a higher dose to the cancer. Many major hospitals and cancer centers now use IMRT, especially for tumors in hard-to-treat areas.

Proton beam radiation therapy

Proton beam radiation uses radioactive particles that travel only a certain distance before releasing most of their energy.

This type of treatment can help treat tumors in small, intricate areas (such as the base of the skull, pelvis, or spine), where it’s very important to limit the radiation dose that reaches nearby healthy tissues.

The machines needed for proton beam radiation are expensive, and not available in all cancer treatment centers.

Intraoperative radiation therapy (IORT)

In some centers, radiation may be given during surgery using a procedure called IORT. This gives a large dose of radiation directly to the area of the tumor. This may be used in challenging cases where typical doses of radiation could not be given safely. The hope is that this approach may also reduce long-term side effects by giving lower doses of radiation. This method is not used often for Ewing sarcoma.

Possible side effects of radiation therapy

The side effects of radiation therapy depend on where the radiation is given and the dose of radiation. Short-term side effects of radiation occur during or shortly after treatment; long-term side effects can take months or years to develop.

Short-term side effects

Side effects in the weeks during and after treatment may include:

• Fatigue
• Hair loss (in the area receiving radiation)
• Skin that may be red, tender, or dry, like a sunburn (in the area receiving radiation)
• Low blood counts (this is more common when radiation is combined with chemo or other drugs)
• Mouth sores, trouble swallowing 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

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. If radiation is given to an arm or leg, scarring may lead to limb length differences or limited movement that may need treatment.

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 pelvis could affect fertility. It is best to talk with your radiation team about what specific long-term side effects you may need to watch for.

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

To lower the risk of serious long-term effects from radiation, doctors try to use the lowest dose of radiation therapy that is still effective. Still, it is important to go to follow-up visits with your (child’s) doctor so that if problems come up, they can be found and treated as early as possible.