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Radiation therapy uses high-energy rays or particles to kill cancer cells.

Osteosarcoma cells are not easily killed by radiation, so radiation therapy doesn’t play a major role in treating this type of cancer. But sometimes radiation can be useful if the tumor can’t be removed completely by surgery. For example, osteosarcoma can start in hip bones or in the bones of the face, particularly the jaw. In these situations, often it’s not possible to remove all of the cancer. After as much of the tumor is removed as possible, radiation is given to try to kill the remaining cancer cells. Chemotherapy is then often given after the radiation.

Radiation can also be used to help slow tumor growth and control symptoms like pain and swelling if surgery is not possible, or if the cancer has come back.

External beam radiation therapy

This is the type of radiation therapy most often used to treat osteosarcoma. A machine outside the body focuses high-energy beams on the tumor to kill the cancer cells.

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. This planning session is called simulation.

Most often, radiation treatments are given 5 days a week for several weeks. Each treatment is much like getting an x-ray, although the dose of radiation is much higher. The treatment is not painful. For each session, you (or your child) will lie on a special table while a machine delivers the radiation from precise angles.

Each treatment lasts only a few minutes, although the setup time – getting into place for treatment – usually takes longer. Young children may be given medicine to make them sleep so they will not move during the treatment.

Newer techniques, such as intensity modulated radiation therapy (IMRT), conformal proton beam therapy, and stereotactic radiosurgery (SRS), let doctors aim the radiation at the tumor more precisely while reducing how much nearby healthy tissues get. This may offer a better chance of increasing the success rate and reducing side effects. Many doctors now recommend using these approaches when they are available. (See What’s New in Osteosarcoma Research?)

Possible side effects of radiation therapy

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

Short-term problems can include effects on skin areas that receive radiation, which can range from mild sunburn-like changes and hair loss to more severe skin reactions. Radiation to the abdomen or pelvis can cause nausea, diarrhea, and urinary problems. Talk with your (child’s) health care team about the possible side effects because there may be ways to relieve some of them.

In children, radiation therapy can slow bone growth. For example, radiation to the bones in one leg might result in it being shorter than the other. Radiation to the facial bones may cause uneven growth, which might affect how a child looks. But if a child is fully or almost fully grown, this is less likely to be an issue.

Depending on where the radiation is aimed, it can also damage other organs:

• Radiation to the chest wall or lungs can affect lung and heart function.
• Radiation to the jaw area might affect the salivary glands, which could lead to dry mouth and tooth problems.
• Radiation therapy to the spine or skull might affect the nerves in the spinal cord or brain. This could lead to nerve damage, headaches, and trouble thinking, which usually become most serious 1 or 2 years after treatment. Radiation to the spine might cause numbness or weakness in part of the body.
• Radiation to the pelvis can damage the bladder or intestines, which can lead to problems with urination or bowel movements. It can also damage reproductive organs, which could affect a child’s fertility later in life, so doctors do their best to protect these organs by shielding them from the radiation or moving them out of the way whenever possible.

Another major concern with radiation therapy is that it might cause a new cancer to form in the part of the body that was treated with the radiation. The higher the dose of radiation, the more likely this is to occur, but the overall risk is small and should not keep children who need radiation from getting it.

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’s important to continue follow-up visits with your (child’s) doctor so that if problems come up they can be found and treated as early as possible.

Radioactive drugs (radiopharmaceuticals)

Bone-seeking radioactive drugs, such as samarium-153-EDTMP (Quadramet) or radium-233 (Xofigo), are sometimes used to slow tumor growth and treat symptoms such as pain in people with advanced osteosarcoma. These drugs are injected into a vein and collect in the bones. Once there, the radiation they give off kills the cancer cells.

These drugs are especially helpful when cancer has spread to many bones, since external beam radiation would need to be aimed at each affected bone. In some cases, these drugs are used together with external beam radiation aimed at the most painful bone metastases.

The major side effect of these drugs is a lowering of blood cell counts, which could increase the risk for infections or bleeding, especially if the blood counts are already low.