Brain Tumors: Radiation

What is radiation therapy?

Radiation therapy uses energy to kill cancer cells. It helps control the growth of some types of brain tumors. It’s often used with surgery or chemotherapy to treat a brain tumor. This type of treatment is done by a doctor called a radiation oncologist.

When might radiation therapy be used?

Radiation therapy may be used:

  • After surgery and sometimes with chemotherapy to try to kill remaining tumor cells in the brain

  • As the main treatment for the brain tumor, if surgery can’t be done

  • To help relieve symptoms caused by a brain tumor

Types of radiation therapy

There are 2 main types of radiation therapy. Your doctor may give you both types of therapy. They include:

  • External beam radiation (EBRT). For this type, a machine directs the rays of energy to the area of cancer.

  • Internal radiation (brachytherapy). This is also called interstitial therapy. Small pellets with radiation are placed inside or near the area with cancer.

EBRT therapy

There are several types of EBRT. These can target the tumor more closely. This can limit the effect that radiation has on other brain cells. Radiation can harm normal brain cells. To limit the harm, your doctor may use types of EBRT such as:

  • 3-D conformal therapy (3DCRT). For this treatment, computers and computed tomography (CT) or magnetic resonance imaging (MRI) scans are used to match the radiation beams to the shape of the tumor from different angles.

  • Intensity modulated radiation therapy (IMRT). This is a similar method that allows doctors to control the intensity of the radiation beams directed at different parts of the tumor. This type of radiation therapy is usually given over several weeks of treatment.

  • Conformal proton beam therapy. This is similar to IMRT. It focuses beams of protons instead of X-rays on the tumor. Protons are more likely to pass through normal tissues without harming them, which may lead to fewer side effects. This type of radiation therapy is also usually given over several weeks of treatment.

  • Stereotactic radiosurgery (SRS). This method can be used on small tumors. Once the size and location of a tumor is known, a high-energy dose of radiation is sent to the tumor from many angles. This type of treatment is given as a single dose. Or it may be given as several doses over a few days. Your doctor may use SRS as the main treatment or as an additional treatment. There are 2 types of SRS:

    • Gamma knife radiation. Radiation beams (gamma rays) from a machine are focused at the tumor from hundreds of angles at the same time.

    • Linear accelerator. Instead of delivering many beams at once, this machine moves around the head to send radiation to the tumor from different angles.

You'll have imaging tests to see if the cancer has spread to other parts of your brain and your spinal cord. If the cancer has spread, you may have radiation to your whole brain and spinal cord.


Brachytherapy is done by inserting radioactive seeds or pellets into or near the tumor. This is done either through tiny tubes or during a surgery. The radiation they give off travels a very short distance. This helps make sure it affects the tumor with very little effect on nearby brain tissue. This method may be used to send a high dose of radiation at the tumor site while EBRT treats nearby areas with a lower dose.

Possible side effects

Radiation treatment affects normal cells as well as cancer cells. It may cause side effects. These depend on how much radiation you get and how it's given. Possible side effects include:

  • Headache

  • Skin irritation

  • Intolerance of cold

  • Nausea and vomiting

  • Tiredness

  • Trouble thinking and remembering

  • Side effects to the area treated, such as hearing loss

  • Problems with your thyroid, hypothalamus, or pituitary glands, which can affect hormone levels in your body

Radiation necrosis

In some cases, dead brain tissue will form at the site of the radiation. This is called radiation necrosis. The mass of dead brain tissue usually has both cancer cells and healthy cells. Radiation necrosis can take anywhere from months to years to develop.

Radiation necrosis may need to be removed with surgery if it causes problems such as:

  • Dementia

  • Headache

  • Seizures

It's not always easy to tell the difference between radiation necrosis and cancer that has come back. A brain scan called a positron-emission tomography (PET) scan can sometimes tell the difference between dead tissue and living cancer tissue. But often a biopsy is the only way to tell for sure.

Risk of future cancer

Radiation can also affect your genes. As a result, after radiation, you have a small risk of getting a second cancer. This second cancer usually occurs many years later. Talk to your radiation oncologist about the risks and benefits of radiation therapy to know your options.