Radiation therapy for brain and spinal cord tumours
Radiation therapy uses high-energy rays or particles to destroy cancer cells. It is usually used to treat brain and spinal cord tumours. Your healthcare team will consider your personal needs to plan the type and amount of radiation, and when and how it is given. You may also receive other treatments.
Radiation therapy is given for different reasons. You may have radiation therapy:
- as your main treatment to destroy the tumour cells when surgery can’t be done and medicines are not effective
- to destroy tumour cells left behind after surgery to reduce the risk that the tumour will come back (recur) (called adjuvant therapy)
- to treat recurrent brain tumours
- to prevent or relieve the symptoms of brain and spinal cord tumours
The following types of radiation therapy are most commonly used to treat brain and spinal cord tumours.
External beam radiation therapy
During external beam radiation therapy, a machine directs radiation through the skin to the tumour and some of the tissue around it. Modern radiation techniques allow doctors to target the area to be treated much more accurately, while sparing as much surrounding normal brain and spinal cord tissue as possible.
Three-dimensional conformal radiation therapy (3D-CRT)
In 3D-CRT, the radiation oncologist uses a CT scan or an MRI to map the exact location and shape of the tumour. Several radiation beams are then shaped and aimed at the tumour from different directions to treat the tumour from all angles.
Intensity-modulated radiation therapy (IMRT)
IMRT is a type of conformal radiation therapy. In addition to shaping and aiming the radiation beams, the strength (intensity) of the beams can be adjusted. This reduces the amount of radiation reaching sensitive areas of the brain, such as the optic nerve, the brain stem and the pituitary gland, while allowing a higher dose to be given to the tumour.
Conformal proton beam radiation therapy
Proton beam radiation therapy is similar to 3D-CRT, but it uses proton beams instead of x-ray beams. X-ray beams release energy before and after they hit their target. Proton beams are different because they release most of their energy after travelling a certain distance and cause very little damage to tissues that they pass through. As a result, more radiation can be delivered to the tumour.
Stereotactic radiation therapy
Stereotactic radiation therapy delivers external beam radiation therapy in very precise amounts to the tumour and surrounding tissue. A CT scan and an MRI are used to create 3-D pictures of the tumour and the surrounding normal brain tissue. This information is used to plan where the radiation will be directed (called the treatment field). A specialized computer program guides the delivery of radiation to the tumour.
Stereotactic radiosurgery (SRS) delivers a single high dose of radiation to the tumour (called a single fraction). This treatment doesn’t involve surgery – no cut (incision) is made and tissue is not surgically removed. SRS may be used for small tumours that are less than 4 cm in diameter. It is also sometimes used for small tumours that have already received radiation therapy.
Stereotactic radiotherapy (SRT) is like SRS, but it gives smaller doses of radiation over a number of treatment sessions (called fractions) until the total dose is given. This is also called fractionated radiosurgery.
Stereotactic radiation therapy may be given with a movable machine that creates radiation called a linear accelerator or with specialized equipment, such as a CyberKnife or Gamma Knife.
Whole-brain and spinal cord radiation therapy (craniospinal radiation therapy)
If the brain tumour has spread to the meninges or the spinal cord, radiation may be given to the whole brain and the entire spinal cord. Some types of tumours, such as medulloblastoma, often spread in this manner and may require craniospinal radiation therapy (CSI) more often than other types of tumours. CSI is sometimes given to prevent a tumour from spreading within the brain and spinal cord (called prophylactic CSI).
Side effects can happen with any type of treatment for brain and spinal cord tumours, but everyone’s experience is different. Some people have many side effects. Other people have few or none at all.
During radiation therapy, the healthcare team protects healthy cells in the treatment area as much as possible. But damage to healthy cells can happen and may cause side effects. If you develop side effects, they can happen any time during, immediately after or a few days or weeks after radiation therapy. Sometimes late side effects develop months or years after radiation therapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.
Side effects of radiation therapy will depend mainly on the size of the area being treated, the specific area or organs being treated, the total dose of radiation and the treatment schedule. Some common side effects of radiation therapy used for brain and spinal cord tumours are:
- nausea and vomiting
- skin problems
- memory loss
- trouble concentrating
- personality changes
Tell your healthcare team if you have these side effects or others you think might be from radiation therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.