Childhood Cancer

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Childhood Brain and Spinal Cord Tumors

Types of radiation therapy

Radiation therapy directs high-energy x-rays at targeted areas of the body to destroy tumor cells or interfere with their ability to grow. Because tumor cells often remain after surgery, radiation is used to destroy them after a biopsy or after total or partial surgical removal of a tumor. Radiation is also used to relieve symptoms, such as pain. When used for pain relief, the treatment is called palliative radiation.

Radiation can be given internally or externally. This section describes the types of radiation that are used to treat children with brain and spinal cord tumors.

External radiation

External radiation uses high-energy x-rays called photons or protons to kill tumor cells. For photon radiation therapy, a large machine called a linear accelerator directs x-rays to the precise portion of the brain or spinal cord where the tumor is located. The treatment is usually given in doses measured in units called gray (Gy).

Radiation oncologists create an individualized treatment plan for each child using computers that combine images from MRIs and CT scans of the tumor and surrounding areas of the brain and spine. This plan allows the radiation oncologist to aim the radiation directly at the tumor or surgical cavity and a small margin around it; this way normal brain tissue can be spared as much as possible.

Radiation is usually given every day for a specific number of days, excluding weekends. This process is called standard or conventional fractionation, and it is the most common way brain and/or spinal cord radiation is given. Radiation given more than once a day is called accelerated fractionation, or hyperfractionation. It uses smaller amounts of radiation for each treatment. Hyperfractionation may reduce long-term side effects, but short-term side effects are sometimes more pronounced.

Specific types of external radiation therapy are:

  • 3D conformal radiation therapy. This type of therapy delivers high-dose radiation tailored to the precise area of the tumor, while delivering a lower dose to the normal tissue surrounding the tumor. It uses 3D images from CT, MRI, and PET scans to identify the margins of the tumor and their relationship to normal brain structures. Multiple radiation beams are delivered from several different directions so that they overlap at the tumor. By using this technology, the tumor receives the high-dose radiation and the normal tissues surrounding it receive a lower dose.
  • Intensity modulated radiation therapy (IMRT). This type of 3D conformal therapy can spare adjacent critical structures by varying the intensity of one beam of radiation. IMRT is the most advanced form of photon radiation available. A disadvantage of this type of radiation is that a lower dose of radiation is given to a larger amount of normal brain tissue.
  • Stereotactic radiosurgery. This sophisticated 3D technique directs radiation to small tumors that cannot be surgically removed because of their location deep within the brain. Using highly specialized computer-assisted equipment, it delivers radiation via multiple independent beams directed to the single target. Stereotactic radiosurgery is delivered as a single treatment (radiosurgery) or as fractionated treatment (stereotactic radiotherapy). This innovative treatment requires precise planning and the combined efforts of multiple specialists. A neurosurgeon works in collaboration with the radiation oncologist to deliver the treatment.

My daughter Stacia’s inoperable tumor (a GBM) located in the basal ganglia was treated with stereotactic radiosurgery by way of focused radiation beams. She had to put on the bird cage, she thought the screws in her head were annoying, and the anesthetic shots in the scalp were a nuisance, but otherwise she was fine. Two months after this treatment, her basal ganglia tumor was completely dark, and she clinically was terrific. Two months after that, recurrence on the edges of the cavity had begun. But in my opinion this treatment was effective in increasing both the quantity and quality of her life.

  • Proton beam radiation. Proton therapy delivers high doses of radiation to the tumor while limiting damage to surrounding healthy tissue. This advanced technique generally results in fewer short- and long-term side effects than does conventional radiation therapy. Proton beam therapy is only available at a few specialized centers, but it will soon be available at some major pediatric centers.

Our daughter Megan (age 8) received proton beam therapy for her optic glioma. She was so full of spunk she would run down the hall with her pink blanket dragging behind her and jump on the table. Megan lay on a table where they placed pliable plastic mesh over her face first to get a mold, then the mask was bolted to a board during treatment. The radiation took about a minute per location, and there were three locations. She had this treatment for 6 weeks; there was no sickness, no skin burning. After proton treatment, the tumor did not grow for about 7 years.

Children do not become radioactive from these types of radiation treatments, and no specific precautions or activity restrictions are necessary.

I was very proud of my 6-year-old son for handling his radiation treatments so well. He never required sedation and was always cooperative. I’m convinced that it was partly because of his personality, and partly because of how the staff treated him. Every day that he received radiation, his favorite stuffed toy, Mr. Bear, was radiated, too.

For a listing of facilities that offer specific kinds of radiation treatment, contact the American Brain Tumor Association, listed in Appendix B, Resource Organizations.

Internal radiation

Internal radiation—also called brachytherapy, implant therapy, or interstitial therapy— is not commonly used to treat childhood brain and spinal cord tumors. Internal radiation uses radioactive materials (called seeds or implants) placed directly into the tumor (interstitial implants) or applied to the surface of the tumor (plaques). It differs from external radiation because it provides a continuous low dose of radiation to the tumor, rather than intermittent bursts one or two times per day.

The radioactive seeds or implants are delivered through a catheter that is placed surgically with CT scan guidance. The catheter remains in place for a specific number of days (usually 2 to 5 days), until the required amount of radiation has been given, and is then removed.

Your child will become radioactive from internal radiation. He will need to stay in a special isolation room with a private bathroom during treatment. The room has plastic covers on all fixtures, and disposable serving plates and utensils are used. Parents are allowed to spend a limited amount of time with their child, typically several hours a day. The rest of the time you can sit outside your child’s room to talk or read to him. Children and pregnant women cannot visit when your child is radioactive.

Although experience with internal radiation in children is limited, efforts are ongoing to evaluate various types of internal radiation in children with recurrent brain and spinal cord tumors.

Experimental treatments used with radiation

Megan had an anaplastic ependymoma in the left occipital/ parietal region of her brain. She had a gross total resection of the tumor. While all of her MRIs were clear following the initial surgery, we all know that you can’t get every cell in surgery and we don’t know how well chemo works on these brain tumors. So, we went with the aggressive approach and (2 ½ years ago now) Megan had a second surgery to implant brachytherapy seeds.

The doctor had 150 seeds ready to be implanted in the tumor bed. Our doctor called us from the operating room, happy and amazed that there were no visible traces of tumor. Five biopsies were done while Megan was in surgery, only one showed traces of tumor. The doctor then removed some tissue in the area where the traces of tumor were and then did five more biopsies in that area. Those five biopsies came back clear. As there was only one area that had any active tumor cells, that is the only area where the seeds were implanted and they only used 34 seeds.

Megan had no side effects, either at the time of surgery or since, from this type of radiation. Her MRIs are still clear and do not show any signs of radiation damage to the area where the seeds were implanted. We do know that some of the seeds have since fallen out of place and rest at the bottom of her spine. The doctors aren’t concerned about this and they don’t affect her.

In some clinical trials, radioimmunotherapy and chemical modifiers are used in conjunction with radiation to treat children with brain and spinal cord tumors.

Radioimmunotherapy uses radiolabeled antibodies as radiation carriers. The antibodies are attached (labeled) to a radioactive material and then injected into the body through a venous catheter or IV. Once injected, the antibodies begin a “seek and destroy” mission, searching for specific tumor cells. Radiolabeled antibodies lessen the chance of radiation damage to normal cells. Experience with this method of radiation in children is limited.

Chemical modifiers are compounds used at the same time as radiation therapy. Two classes of compounds are currently under study in children: radiation sensitizers and radioprotectors (drugs that are administered with the radiation treatments). Radiation sensitizers increase delivery of oxygen to tumor cells, thereby rendering them more sensitive to the effects of radiation. Radioprotectors are designed to shield normal cells from radiation damage by using substances absorbed by healthy normal cells but not by tumor cells. Studies using these compounds are ongoing or under development in the Children’s Oncology Group and may provide important new ways to treat children with brain and spinal cord tumors.

Parts of the body where radiation is usedWho needs radiation treatment?

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