External beam radiation therapy

Friday 1 December, 2017

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On this page:  The treatment course | Planning the treatment | What to expect at treatment sessions | Imaging scans you may have | Techniques and types of EBRT | Key points


External beam radiation therapy (EBRT) uses a radiation machine to precisely direct radiation beams at the cancer. The radiation is targeted only at the part of the body where the cancer is; for example, if you have breast cancer, the radiation will treat only the breast.

You will lie on a treatment table or “couch” under the machine, which will usually be a linear accelerator (see illustration below). The machine does not touch you, but it may rotate around you to deliver radiation beams to the area of the cancer from different directions. This allows the radiation to be more precisely targeted at the cancer and limits the radiation to surrounding normal tissues. You won’t be able to see or feel the radiation. Once the machine is switched off, it no longer gives off radiation.

Linear accelerator

This is a general illustration of a linear accelerator (linac), the most common type of radiation therapy machine. The machine used for your treatment may look different.

Linear accelerator

The treatment course

Your radiation oncologist will work out the total dose needed to treat the cancer. In most cases, this will then be divided into several smaller doses called fractions that are given on different days. Each session lasts about half an hour, with the treatment itself taking only a few minutes.

A course of treatment refers to the total number of sessions of radiation therapy you receive. The length of the course varies between people depending on the type of cancer, the total dose required, the location of the cancer and the reason for having the treatment.

In general, higher total doses are used for curative treatment, and a fraction will be given each day, Monday to Friday, for 3–8 weeks.Dividing the dose into separate sessions with weekend rest breaks allows the healthy cells to recover. Occasionally, the radiation oncologist may recommend two treatments per day, with several hours between the sessions.

If you are having radiation therapy as palliative treatment to relieve symptoms, you may have only one or a few treatments.

Each fraction of radiation causes a little more damage to cancer cells, so it’s important to attend all of your scheduled sessions. This ensures you receive the required amount of treatment to eventually kill the cells or relieve symptoms. When you miss sessions, cancer cells have more time to repair the damage, so your treatment may become less effective.

Planning the treatment

Treatment needs to be carefully planned to ensure that enough radiation reaches the cancer, while as little as possible reaches healthy tissues and organs. The planning steps below may occur over a few appointments.

Initial appointment and examination

This may take up to two hours. Your radiation oncologist will assess whether radiation therapy is the right treatment for you. This will involve talking to you, doing a physical examination, and looking at all your tests and scans.

The benefits and side effects of radiation therapy and what to expect during planning and treatment will be explained. You might also meet the radiation oncology nurse and a radiation therapist who can give you more information.

The radiation oncologist may arrange further x-rays, scans or other tests to find out more about the cancer.

You may want to take someone with you to keep you company, ask questions and make notes.

Masks and casts

In most cases, you will need some type of device to ensure you are in the same position for each session and to help keep you still during treatment. This is known as an immobilisation device or cast and it will be custom-made to fit you. Depending on the area being treated, the device could be a mask, head rest, breast board, or a knee or foot cushion.

For radiation therapy to the head or neck, you may need to wear a plastic mask. This can feel strange and confining, but you will still be able to hear, speak and breathe. Tell the radiation therapists if you feel anxious or claustrophobic before or during treatment. They can suggest breathing or relaxation exercises, or arrange for you to have a mild sedative.

Skin markings

To ensure you are positioned in the same way for each treatment session, a few very small permanent ink spots (tattoos) may be marked on your skin. These tattoos are the size of a small freckle and can't be easily seen.

Sometimes temporary ink marks are made on the skin. Ask the radiation therapist if you can wash these off or if you need to keep them until the full course of treatment is finished. The ink can be redrawn during the course of treatment, but it will gradually fade.

If you have to wear a mask or cast, the markings may be made on this rather than on your skin.

For image-guided radiation therapy, you may have a small surgical procedure to insert markers (usually gold grains) into the cancer. These internal markers can then be seen on scans during the treatment.

CT planning

You will need to have a planning CT scan even if you have already had a CT scan to diagnose the cancer. This step is known as CT planning or simulation.

For this scan, you will be placed in the same position on the table that you will be in for treatment. If you have a mask or cast, you will use it during the scan. The images from the CT scanner will build up a three-dimensional picture of your body. This will show the exact location that needs to receive the radiation.

The radiation therapists will send the images from the scans to a computer. This allows the radiation oncologist to outline exactly where they need to treat. The oncologist will prescribe the appropriate dose of radiation therapy, which will help the medical physicist and therapists to precisely plan your treatment.

The information in this section will apply in most cases, but you may find that things are done slightly differently where you have treatment. Visit Radiation Oncology's website to watch a video explaining the radiation therapy process.

What to expect at treatment sessions

There will be at least two radiation therapists at each treatment session. They may ask you to change into a hospital gown before taking you into the treatment room. You will be able to leave your belongings in a secure locker. The treatment room will be in semi-darkness so the therapists can see the light beams from the treatment machine and line them up with the tattoos or marks on your body or mask.

If you are having image-guided radiation therapy, the radiation therapists will take x-rays or a CT scan to ensure you are in the correct position on the treatment table. They may move the table or physically move your body. They will check the scans straightaway and make any adjustments needed.

Receiving the treatment

Once you are in the correct position, the radiation therapists will go into a nearby room to operate the machine. You will be alone in the treatment room, but you can talk to the therapists over an intercom, and they will watch you on a television screen. The therapists will move the machine automatically from outside the treatment room if necessary.

The machine will not touch you. You won't usually see or feel anything unusual, but you may hear a buzzing noise from the machine while it is working and when it moves.

It is important to stay very still to ensure the treatment targets the correct area. The radiation therapists will tell you when you can move. If you feel uncomfortable, tell the therapists – they can switch off the machine and start it again when you're ready. You will usually be able to breathe normally during the treatment. For some radiation to the chest area, you may be instructed to take a deep breath and hold it while the radiation is delivered.

The treatment itself takes only a few minutes, but each session may last 10–20 minutes because of the time it takes the radiation therapists to set up the equipment and put you into the correct position. You will be able to go home once the session is over. You will see the radiation oncologist, a registrar (doctor training in radiation oncology) or radiation oncology nurse regularly during a course of treatment to check how you are going.

Managing anxiety

The treatment machines are large and kept in an isolated room. This may be confronting, especially at your first treatment session. Some people feel more at ease with each session as they get to know the staff, procedures and fellow patients. If you are afraid of confined spaces (claustrophobic) or feel anxious, let the radiation therapists know so they can help you.

Discomfort during treatment

EBRT itself is painless – you won't feel it happening. You may feel some discomfort when you're lying on the treatment table, either because of the position you're in or because of pain from the cancer. In this case, talk to the radiation oncology nurse about whether to take pain medicine before each session.

Some people who have treatment to the head say they see flashing lights or smell unusual odours. These effects are not harmful, but tell the radiation therapists if you experience them.

Safety precautions

EBRT does not make you radioactive because the radiation does not stay in your body during or after treatment.

You will not need to take any special precautions with bodily fluids (as you would with chemotherapy). It is safe for you to be with family, friends, children and pregnant women and for them to come into the radiation therapy centre with you. However, they cannot be in the room during the treatment.

Imaging scans you may have

During planning and treatment, you may need to have some of the following tests to show the exact position and shape of the cancer.

X-ray

Powerful invisible radiation passes through the body and creates an image on x-ray film, with black areas representing soft tissues and lighter areas showing denser tissues, such as bones.

CT scan

CT stands for computerised tomography scan. It uses x-ray beams and computer technology to create a detailed, crosssectional picture of the inside of the body. You may be given an injection of a dye to make the images clearer. The CT scanner is large and round like a doughnut and you will lie on a table that moves in and out of the centre of the doughnut.

MRI scan

MRI stands for magnetic resonance imaging scan. It uses radio waves and magnetism to create cross-sectional pictures of the inside of the body. You may be given an injection of a dye before the scan. You will lie on a table that slides into a narrow metal cylinder. The machine can be quite noisy.

PET scan

PET stands for positron emission tomography scan. It involves an injection of a small amount of radioactive glucose solution. Cancerous areas take up more of the glucose and show up brighter on the scan.

PET-CT scan

This combines a PET scan and a CT scan in one machine. The machine looks similar to a CT scanner.

Ultrasound

A device is placed on or in your body to send out high frequency soundwaves that you won't be able to hear. The soundwaves are reflected when they meet something dense, like an organ or tumour. A computer then creates a picture from these soundwave reflections.

Your treatment team will explain what to expect from each test, or you can call Cancer Council 13 11 20 for more information.

Techniques and types of EBRT

EBRT can be given using different techniques and different types of radiation. Your treatment centre may not offer all methods, but your radiation oncologist will recommend the most appropriate combination for you.

Three-dimensional conformal radiation therapy (3DCRT)

  • Common type of EBRT.
  • Uses imaging scans (see above) to help plan the treatment.
  • A computer uses the scans to precisely map the location of the cancer within the body.
  • The radiation is then shaped (conformed) so that the cancer receives most of the radiation, and surrounding tissues receive much less.

Intensity-modulated radiation therapy (IMRT)

  • Highly accurate type of conformal radiation therapy.
  • Shapes and divides multiple radiation beams into tiny beams (beamlets) that vary in strength.
  • Widely used for most cancer types, especially for curative treatment.
  • Volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) are specialised forms of IMRT that use a treatment machine that rotates around the body.

Image-guided radiation therapy (IGRT)

  • Uses a treatment machine that takes x-rays or scans at the start of each session.
  • Markers (usually grains of gold) may be inserted into the cancer so they can be seen in the x-rays or scans.
  • Positioning can be very finely adjusted, often to millimetre accuracy.
  • Radiation oncologists may recommend IGRT for areas likely to be affected by movement, such as the lungs and liver when you breathe, or the prostate when the fullness of your bladder or bowel varies.

Stereotactic radiosurgery (SRS)

  • Specialised type of radiation therapy.
  • Combines many small radiation fields to give precisely targeted radiation in one single high dose.
  • Used to treat small cancers in the brain while minimising the radiation reaching healthy brain tissue.
  • A custom-made mask keeps the head still during SRS.
  • Despite the name, this is not surgery and does not involve any surgical cuts.

Stereotactic body radiation therapy (SBRT)

  • Similar to SRS, this method allows a few high doses of radiation to be delivered very precisely.
  • May be used to treat small cancers in the body, including small lung or liver cancers or small metastases (cancer that has spread away from the primary cancer).
  • Sometimes called stereotactic ablative body radiation therapy (SABR).

Proton therapy

  • Uses radiation from protons rather than x-rays.
  • Protons are tiny parts of atoms with a positive charge that release most of their radiation within the cancer – useful when the cancer is near sensitive areas, such as the brainstem or spinal cord, especially in children.
  • Special machines, known as cyclotrons and synchrotrons, are used to generate and deliver the protons.
  • Proton therapy is not yet available in Australia (as at December 2017), but there is funding in special cases to allow Australians to travel overseas for treatment.

Jackie's story

"I was diagnosed with early-stage breast cancer after a routine mammogram. I had surgery, and my doctor recommended I have radiation therapy as well.

"At my first appointment with the radiation oncologist, she explained what radiation therapy is and described what would happen during each session. She told me the radiation therapist would give me small tattoos to make sure the treatment reached the same area each time. I don't like tattoos, and it really caught me by surprise that I had to get them. As it turns out, they're very small and I didn't feel any pain having them.

"At the planning appointment, the radiation therapists placed me in the position I would be in at each session. They told me I had to keep very still to make sure the treatment was effective. I saw the room where I would be having treatment, which was really helpful as it meant I knew what to expect at my first session.

"I had treatment Monday to Friday for six weeks. Some days I had treatment very quickly, and on other days I had to wait a bit longer. I passed the time by reading a book or doing puzzles. The actual treatment took only a few minutes each visit. I didn't find it hard to keep still, as the therapists positioned me very well and I was kept in place with a mould shaped like a wedge.

"T"owards the end of the six weeks, I started to feel very tired and I would sleep a lot. The nurses gave me cream and gel to put on the skin of the treatment area. I used it every day as soon as treatment started and for a short time after it finished. I developed dark marks that looked like burns, but most of them have faded."

Tell your cancer story.

Key points

  • In EBRT, radiation is directed at the cancer from a special machine, usually a linear accelerator.
  • The treatment is painless and does not make you radioactive. The radiation can't be seen or felt.
  • The length of treatment course will vary depending on the type of cancer, the prescribed dose, and the aim of treatment. Most curative treatments occur Monday to Friday for 3–8 weeks.
  • Most people will need a special device, such as a cast, mask or mould, to keep them still and in the same position during treatment sessions.
  • Your radiation therapists will put small marks (dots of ink or tattoos) on your skin to help them position you correctly each time.
  • During the CT planning appointment, the radiation therapists will use a CT scan to work out exactly where to direct treatment. You may also have other scans, such as an MRI, a PET scan or ultrasound. The scans will help the radiation oncologist to prescribe the correct dose to the exact location of the cancer.
  • Most sessions last for 10–20 minutes. The radiation therapy itself takes only a few minutes. Most of the time is spent setting up the equipment and placing you in the correct position.
  • You will lie on a table called a treatment couch. The radiation therapists will be in the next room to control the machine. They will be able to see you and talk with you through a speaker, and they can pause the treatment if necessary.

Reviewed by: Dr Tiffany Daly, Radiation Oncologist, Radiation Oncology Princess Alexandra Raymond Terrace (ROPART), South Brisbane, QLD; Elly Keating, Acting Principal Radiation Therapist, Northern Territory Radiation Oncology, Alan Walker Cancer Care Centre, NT; Julie O'Rourke, Clinical Nurse Consultant, Radiation Oncology, Canberra Hospital, ACT; Ching Tsao, 13 11 20 Consultant, Cancer Council NSW; A/Prof Sandra Turner, Clinical Lead, Targeting Cancer Campaign, Faculty of Radiation Oncology, Royal Australian and New Zealand College of Radiologists (RANZCR), NSW; Dr David Waterhouse, Acting Principal Radiation Oncology Medical Physicist, Sir Charles Gairdner Hospital, WA; David Wells, Consumer.

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