External beam radiation therapy (EBRT)

External beam radiation therapy (EBRT) is the most common type of radiation therapy. It directs high-energy radiation beams at the cancer.

Learn more about:

• How EBRT works
• The linear accelerator
• The treatment course
• Planning the EBRT treatment
• What to expect at treatment sessions
• Imaging scans you may have
• Common types of EBRT
• Specialised types of EBRT

How EBRT works

EBRT is delivered using a radiation machine. The most common type is a linear accelerator (see below).

You will lie on a treatment table or “couch” under the machine. The machine does not touch you, but it may rotate around you to deliver radiation to the area with cancer from different directions. This allows the radiation to be more precisely targeted at the cancer and limits the radiation given to surrounding normal tissues.

Linear accelerator

This is a general illustration of a linear accelerator (LINAC). It’s large and often kept in a separate room. A CT scan machine is usually attached to the linear accelerator. The machine used for your treatment may look different. There may also be imaging devices on or near the linear accelerator, which help position you accurately on the couch

The treatment course

After the planning session, your radiation oncologist will work out the total dose of radiation needed to treat the cancer and the total number of treatments.

Fractions – In most cases, the total dose will be divided into a number of smaller doses called fractions, which are given on different days. The length of each session will depend on the type of EBRT.

Course – A course of treatment refers to the total number of sessions of radiation therapy. How often and how long you need to have radiation therapy depends on the type of cancer, the total dose required, the location of the cancer and the aim of treatment.

Radiation therapy is personalised and your radiation oncologist will tell you how many treatments you will have. In general, higher total doses of radiation are used for curative treatment. A fraction of the dose will usually be given once a day, Monday to Friday, for 3–8 weeks. Dividing the total dose into separate sessions with weekend rest breaks allows the healthy cells time to recover. Occasionally, you may have two treatments a day, with usually six hours between the sessions.

A course of radiation therapy used to relieve symptoms (palliative treatment) is usually shorter. You may have 1–15 sessions. Palliative radiation therapy may not be given every day.

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