Radiation therapy for brain and spinal cord tumours

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

Most people with brain and spinal cord tumours have radiation therapy. Your healthcare team will use what they know about the cancer and about your health to plan the type and amount of radiation, and when and how it is given.

Radiation therapy is given for different reasons. You may have radiation therapy to:

• treat the tumour when surgery can’t be done
• destroy tumour cells left behind after surgery to reduce the risk that the tumour will come back (recur) (called adjuvant therapy)
• treat recurrent brain and spinal cord tumours
• relieve pain or control the symptoms of brain or spinal cord tumours that have spread within the central nervous system

The following types of radiation therapy are most commonly used to treat brain and spinal cord tumours.

During external radiation therapy, a machine directs radiation through the skin and bone to the tumour and some of the tissue around it. External radiation therapy is also called external beam radiation therapy.

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) has many beams of radiation directed at the tumour. The radiation oncologist uses a CT scan or an MRI to map the exact location and shape of the tumour. The radiation beams are then shaped and aimed at the tumour from different directions to treat the tumour from all angles. Each individual beam is fairly weak and less likely to damage normal tissue. A higher dose of radiation is delivered where the beams meet at the tumour.

Intensity-modulated radiation therapy (IMRT) is similar to 3D-CRT in that it delivers radiation from many different angles to treat the entire tumour. In addition to shaping and aiming the radiation beams, IMRT allows the radiation oncologist to adjust the strength (intensity) of the individual beams. This reduces the dose of radiation reaching nearby normal tissue while allowing a higher dose to be delivered to the tumour. It is useful for treating tumours in hard-to-reach areas.

There are different types of stereotactic radiation therapy.

Stereotactic body radiation therapy (SBRT) delivers precisely targeted high doses of radiation to tumours in difficult or hard-to-reach areas in fewer sessions. It is also called stereotactic ablative radiation therapy (SABR). The majority of SBRT is delivered by modern linear accelerators, but it can also be delivered with a CyberKnife unit. It creates many beams of radiation from different angles that meet at the tumour. The tumour itself receives a high dose of radiation while the individual beams that travel through surrounding tissue are a low dose. This lowers the effects of radiation on healthy tissue surrounding the tumour. SBRT is given in fewer treatments than standard external radiation therapy.

Stereotactic body radiation therapy may be used for recurrent brain and spinal cord tumours, because the radiation beams are focused on the tumour, without affecting areas of the brain or spinal cord that may have already had radiation therapy treatment.

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 across. 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 several treatment sessions (called fractions) until the total dose is given. This is also called fractionated radiosurgery.

If the brain tumour has spread to the meninges or the spinal cord, radiation therapy may be given to the whole brain and the entire spinal cord. This is called craniospinal radiation therapy (CSI).

CSI is sometimes given to prevent a tumour from spreading within the brain and spinal cord (called prophylactic CSI).

Proton therapy uses protons (positively charged particles) to treat cancer. It may also be called proton beam therapy. Proton therapy uses proton beams instead of x-ray beams. Protons release more energy after reaching a certain distance and then stop, while x-ray beams release energy before and after they hit their target. So protons cause less damage to tissues they pass through before reaching their target. Proton therapy causes the least amount of damage to nearby normal tissues. A machine called a synchrotron or cyclotron produces the protons.

Brain tumours that are found near the base of the skull and spinal cord tumours may be treated with proton therapy.

Proton therapy machines are not available in Canada. Your healthcare team may arrange for you to go to certain centres in the US to receive this treatment, if you have the type of tumour that is best treated with proton therapy.

During radiation therapy, your healthcare team protects healthy cells in the treatment area as much as possible. 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. Tell your healthcare team if you have side effects that you think are from radiation therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

These are common side effects of radiation therapy for brain and spinal cord tumours:

• fatigue
• nausea and vomiting
• skin problems
• cognitive problems, including personality changes
• headaches

Find out more about radiation therapy and side effects of radiation therapy. To make the decisions that are right for you, ask your healthcare team questions about radiation therapy.