Stereotactic radiotherapy (SBRT) gives radiotherapy from many different angles around the body. The beams meet at the tumour. This means the tumour receives a high dose of radiation and the tissues around it receive a much lower dose. This lowers the risk of side effects.
Usually you have between 1 and 8 treatments.
You might hear the term stereotactic radiosurgery (SRS), this means stereotactic treatment to the brain.
When you might have stereotactic treatment
This type of radiotherapy is mainly used to treat very small cancers, including:
cancer in the lung
cancer that started in the liver or cancer that has spread to the liver
cancers in the lymph nodes
spinal cord tumours
cancer spread in the brain
Stereotactic treatment can also treat areas that have previously been treated with radiotherapy. For example, if someone has already had radiotherapy to their pelvis they usually wouldn’t be able to have radiotherapy again. But because stereotactic treatment is so precise it can often mean re-treatment is possible.
You start with a session in the radiotherapy department. You have a CT scan.
You may also have MRI scans or PET scans of the area of the body to be treated. The information from these scans feeds directly into the radiotherapy planning computer.
The computer programme then designs radiation beams that follow the shape of the tumour very closely.
Your doctor makes sure that all of the tumour is inside the radiotherapy field and healthy tissue is avoided as much as possible. This reduces the risk of side effects.
After the planning session you usually have to wait a few days or up to 2 weeks for the physicist and your radiotherapy doctor to create your treatment plan.
You then get an appointment for your first session of radiotherapy.
Having SBRT treatment
To have the treatment you lie on a radiotherapy couch. The radiographers help you to get into the right position and put on any moulds that you may need.
Different machines can be used to give stereotactic radiotherapy.
The most commonly used one is a Linear Accelerator (LINAC). But you might also have it on a CyberKnife machine.
SBRT with a LINAC
Once you are in the right position the staff leave you alone in the room. This is so they are not exposed to radiation.
You will be alone for the treatment, which lasts between 15 minutes to 2 hours. It can sometimes last longer than this. You might have the treatment in one go or it may be broken up with short breaks.
The radiographers can speak to you by intercom and they can see and hear you the whole time. It is important that you stay very still throughout the treatment.
You won’t feel anything and the machine doesn’t touch you.
The machine will beep from time to time. Once the treatment is over the radiographers come in and help you get down from the treatment couch.
SBRT with a CyberKnife machine
The CyberKnife radiotherapy machine has a robotic arm that moves around the treatment couch to give doses of radiation from different angles.
The radiotherapy machine usually takes x-rays every 10 to 20 seconds. The robotic arm uses x-rays to correct its position. This allows your radiographers to target radiotherapy beams accurately at the tumour, even if the tumour moves as you breathe.
Treatment may take between 30 minutes to 4 hours depending on the type of cancer and the position of the tumour in the body. CyberKnife can treat multiple tumours at the same time. So it can be very useful for areas of cancer spread.