In external radiotherapy high-energy x-rays are directed at the cancer from a machine outside the body. Different types of machines may be used, and they each vary slightly in how they look and how they work. The machine used will depend on the part of your body being treated and why radiotherapy is being given. Some are better at treating cancer near the skin, others are better for cancers deeper in the body.
Often external radiotherapy is given using a machine called a linear accelerator. Several specialised types of external radiotherapy may be used to treat certain cancers, such as three-dimensional conformal radiation therapy (3D-CRT), intensity modulated radiation therapy (IMRT) and image guided radiation therapy (IGRT). Many of these techniques allow the radiation beams to be delivered from several different directions. This reduces the amount of radiation to normal tissues.
How long is a course of treatment?
A course of treatment refers to the number of treatments.
The number of radiotherapy treatments needed varies between people depending on the total dose required to treat your cancer, its location and the reason for the treatment. In general, higher doses are given for curative treatment and usually over a longer period of time.
The total dose is usually divided into smaller doses called fractions. Most people have radiotherapy Monday to Friday for 6-8 weeks. Weekend rest breaks allow the normal cells to recover. Some people have only one or a few treatments, and occasionally, two treatments per day may be recommended.
Each dose of radiation causes a little more damage to cancer cells, so it’s important you go to all your scheduled sessions to ensure you receive enough radiation to eventually kill the cancer cells or relieve symptoms.
Where will I have treatment?
External radiotherapy is usually given in hospital or at a treatment clinic.
If you have to travel to treatment, you may be able to get some practical support, such as accommodation or financial assistance. Speak to the hospital social worker for more information.
How is treatment planned?
Before you start radiotherapy treatment it will need to be planned. This is an important part of radiotherapy and may take several visits. Planning helps ensure that enough radiation reaches the cancer but does as little damage as possible to the surrounding healthy tissues and organs. Planning consists of several steps:
- Examination: Your radiation oncologist will examine you and may request further x-rays or scans to find out more about the cancer. They will then decide which part of your body to treat, how much radiation to use (the dose) and the number of treatments you will have.
- Planning appointment: Your planning appointment may take several hours but the actual treatment will be much shorter.
- Simulation: You will be asked to lie still on a table while the radiation therapist uses a special x-ray machine called a simulator to pinpoint the exact area on your body where the radiation beams will be aimed. This is like having an x-ray but may take a little longer. At the same time, a radiation therapist will take measurements of you.Some simulators use CT (computerised tomography) scans instead of x-rays. A CT scan takes pictures of the cancer from different angles to build up a three-dimensional picture of the area. You will lie in exactly the same position as when you have your treatment. You may also have an MRI (magnetic resonance imaging) scan, PET (positron emission tomography) scan or an ultrasound.
The measurements and the information from the scans are fed into a computer that helps the radiation oncologist plan your treatment precisely.
- Moulds and casts: Depending on the type of radiotherapy treatment you receive, you may need a special device to help keep an area of your body still during treatment sessions so that radiation is directed at the same place each time. For example, if you need radiotherapy to the head and neck area you will wear a plastic mask called a shell or cast, and markings (see below) can be made on the shell rather than your skin. You will be able to hear, speak and breathe normally while wearing the shell, but it may feel strange and claustrophobic at first. Tell the staff if you feel worried or anxious as they may be able to offer you strategies to help you cope.
- Skin markings: To ensure the radiation is aimed at exactly the same position at each treatment session, two or three very small semi-permanent ink marks or tattoos may be placed on the skin. These tattoos are less than the size of a freckle and are too small to be seen easily. If marks are made on your skin, ask the radiation therapist if you can wash off the ink or if you need to keep it until your full course of treatment is finished. The ink will gradually fade, but it can be redrawn periodically during the course of your radiotherapy treatment.
- You will probably be asked to change into a hospital gown before going into the treatment room.
- You will probably be in this room for 15-20 minutes. You will only have radiation for 1-5 minutes, depending on the dose prescribed. The rest of the time is spent positioning you and setting up the equipment. The room will be in semi-darkness while this is done.
- If you have had a support device made (such as a mask), it will be used during treatment.
- A shield made of thick lead-like metal may be placed between the machine and the parts of the body not being treated to protect them. This is called a multileaf collimator. An extra piece of rubber-like material or a block of specially made wax may also be placed on the skin. This makes sure that the skin gets the computer-planned dose of radiation.
- Once you and the machine are in the correct position, the radiation therapist will go to a nearby room to operate the machine. You will be alone in the room, but you can talk to the radiation therapist over an intercom, and they will watch you all the time on a television screen or through a window.
- You can breathe normally during treatment but you need to stay very still while the machine is working. This ensures that the treatment is accurate. You can often listen to music while you are having radiotherapy to help you relax.
- If treatment is needed from different angles, the radiation therapist will move the machine several times. This is often done from outside the treatment room. It is important that you remain still while the machine is being rotated around the treatment table. The radiation therapist will tell you when it is okay to move. If you feel uncomfortable, tell the therapist as they can switch off the machine and start treatment again when you’re ready.
Will radiotherapy be painful?
No, radiotherapy is painless. During treatment you will not see or feel anything, but you may hear the machine buzzing. You may find that while lying on the treatment table you have pain due to the cancer or discomfort from the position you are in. If you feel ill, tell the radiation therapist, who will pause the treatment.
Will I be radioactive?
No. External radiotherapy does not make you radioactive because the radiation doesn’t stay in your body. It is safe for you to be with children, family and friends, and anyone who might be pregnant. This includes throughout the course of treatment and afterwards.