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External beam radiation therapy is also called external radiation therapy or teletherapy. A machine directs a beam of radiation through the skin to the tumour and a small amount of normal surrounding tissue. This approach can treat larger areas of the body or more than one area, such as the tumour and nearby lymph nodes. Most people who have radiation therapy for cancer receive external beam radiation.
External beam radiation therapy:
Each treatment session can last 15–30 minutes because it takes times to properly position the person and set up the equipment. It usually only takes a few minutes to give the dose of radiation. Total body irradiation (TBI) sessions can last up to 30 minutes.
External beam radiation therapy is given with machines that direct beams of high-energy rays or particles, including:
When radiation is one of the main cancer treatments, it is usually given once a day, 5 days a week, for about 3–8 weeks, with a rest on the weekend. Giving treatments over several days, rather than a single treatment, allows normal cells to recover and repair themselves.
Occasionally, treatments are given more than once a day or every other day. This depends on:
When radiation therapy is given to relieve symptoms caused by advanced cancer (palliative radiation therapy), the course of treatment is shorter, such as a few days or weeks.
The radiation oncologist (a doctor who specializes in treating cancers using radiation therapy) decides on the total dose of radiation that will be given to kill cancer cells and spare normal cells as much as possible. This dose is divided into a number of smaller doses called fractions. Fractionation schedules can vary.
Linear accelerators (LINACs) or cobalt-60 machines are used to deliver external beam radiation. Different models of linear accelerators produce varying amounts or voltages of energy. The kind of machine used depends on the location, depth, type and extent of the tumour being treated.
Other types of external beam radiation therapy include:
A simulation is a planning session that takes place at a cancer treatment centre before the first radiation treatment. It is done to decide the dose of radiation and plan the treatment sessions precisely. The healthcare team makes sure the radiation is aimed at exactly the same area each time treatment is given.
Simulation is usually done in one session and takes anywhere from 15 minutes to an hour or more.
Receiving radiation therapy can be a frightening experience if children don’t know what is happening to them. Because they are frightened, children may not want to or can’t cooperate during the treatment process. Helping children understand what is happening and preparing them for treatment will reduce their fears and will allow them to work with the radiation therapy team.
Children and parents are usually given a tour of the radiation department and treatment room so they can see what the machines look like. Children are often less fearful of a big machine if they see it with their parents first and understand how it works before being treated.
All radiation therapy centres in Canada now have access to a special educational interactive DVD. Children and their families can explore this DVD on their home computer to learn more about what is involved in receiving radiation therapy. (This DVD was developed by Princess Margaret Hospital and Sick Kids Hospital in Toronto, ON.)
Children who are awake and don’t need a sedative might become bored during the treatment.
The machines used for external beam radiation therapy are quite large. They may make strange buzzing noises as they work. The machines may also move around to deliver the radiation from different angles.
A light sedative (anesthetic) is usually given to children under 4 years of age to help them lie perfectly still during the radiation treatment session. Children between 4 and 6 years of age may need a sedative, depending on their ability to understand why they have to lie still, their level of activity and their level of anxiety. In some cases, children in this age group may need sedation at the beginning, but over the course of the treatment they may gradually learn ways to hold still without sedation. Children over 7 years old usually do not need sedation.
External beam radiation therapy is given in the radiation therapy department of a cancer treatment centre, usually on an outpatient basis. Having external beam radiation therapy is similar to having an x-ray. Before external beam radiation treatment, the person may need to change into a hospital gown. They also need to remove anything metal, such as jewellery, zippers or diaper pins, in the treatment area (treatment field). Anything with tight elastic, such as socks or diapers, should be loosened or removed.
During the treatment session:
The radiation oncologist monitors the person’s progress throughout the course of treatment and adjusts the dose or length of treatment as necessary. The radiation therapy team often take special x-rays (port films) during treatment. They review these x-rays to ensure the treatment beam stays on target. Sometimes blood tests, x-rays or other tests are done during the course of treatment to see how the tumour is responding to treatment.
Occasionally, radiation therapy treatments may need to be stopped temporarily if side effects are severe. Missed treatments can be made up later.
External beam radiation doesn’t make a person radioactive. It is safe to be around other people, including children, right after treatment.
Some people can work and continue to do their regular leisure activities while receiving radiation therapy. Others find they tire easily and need to rest more.
The Canadian Cancer Society is actively lobbying the federal government to establish a national caregivers strategy to ensure there is more financial support for this important group of people.