Radiation therapy uses high energy x-rays to destroy tumor cells. A radiation specialist will customize the treatment dose for individual needs. The goal is to try shrink as much of the tumor as possible while minimizing harm to healthy tissue. Radiation therapy is generally most effective when used in combination to other treatments, such as surgery and chemotherapy. It may be used to destroy remaining cancer cells after surgery, or as an alternative for people who can not tolerate surgery.

Different types of radiation therapy are used to treat brain tumors.

External Beam Radiation

In external beam radiation therapy, radiation is produced by a machine positioned outside the body. Short bursts of x-rays are directed at the tumor site. The radiation specialist will direct the radiation beam to affect as much of the tumor as possible.

Radiation is most often given over a number of sessions. In select scenarios, single doses of focused radiation may be of benefit. Repeat radiation to the same area increases the risk of normal brain tissue being destroyed. The radiation specialist will carefully consider the benefits and risks when discussing treatment options.

Craniospinal radiation is a special type of radiation that treats the whole brain and spinal cord. This is done when cancer has spread to the meninges (layers of tissue that cover the brain and spinal cord) or cerebrospinal fluid.

Radiation therapy can be given to treat the tumor or help resolve problems that the tumor(s) may be causing, such as pain and weakness.

Radiation of a Tumor
Diagram of modified radical mastectomy
Copyright © Nucleus Medical Media, Inc.

Delivery methods help to deliver the maximum amount of radiation possible to the tumor while minimizing exposure to healthy surrounding tissue. Methods to improve delivery include:

  • 3D conformal radiation therapy (3D-CRT)—Imaging tests are used to map the brain. Once the tumor is located, radiation beams are directed at it from different angles.
  • Intensity modulated radiation therapy (IMRT)—A computerized machine rotates around the patient to deliver radiation to the tumor site. Dosage can be weakened or strengthened depending on the target tissue.
  • Conformal proton beam radiation therapy—Uses proton beams instead of standard x-rays. Because it is less damaging to normal tissue, a higher dose of radiation can be directed at the tumor.


Brachytherapy implants a device that holds radioactive material directly in or near the tumor. This treatment has been used with some success in the management of small brain tumors. The tumor generally needs to be an inch or less in diameter.

Stereotactic Radiosurgery

Stereotactic radiosurgery is a type of external radiation therapy that can deliver radiation in a very precise location. This allows delivery of higher doses of radiation because it can precisely deliver it to the tumor and not healthy tissue. The precise delivery may also require fewer doses than traditional radiation therapy.

Stereotactic radiosurgery is not available everywhere and is not appropriate for every type of tumor. It is most often appropriate for brain tumors that have spread from other areas of the body.

Side Effects and Management

Radiation therapy is more localized than chemotherapy, which may reduce overall side effects. However, radiation can damage nearby healthy brain tissue which may cause some functional problems. Side effects of radiation therapy may include:

  • Difficulties with brain function, such as memory loss or problems concentrating (these can vary depending on the area of the brain treated)
  • Fatigue
  • Irritability
  • Headaches (uncommon)
  • Nausea and vomiting (uncommon)

A variety of treatments are available to help manage side effects including medication, lifestyle changes, and alternative treatments. In some cases, the radiation therapy regimen may be adjusted to reduce severe side effects. The earlier the side effects are addressed, the more likely they will be controlled with a minimum of discomfort.

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