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7-minute read

Key facts

  • Radiotherapy (radiation therapy) uses radiation aimed at a specific area of the body to kill cancer cells.
  • It can come from a source outside your body or from sealed devices that are put inside your body.
  • The type of radiotherapy used will depend on the cancer, its location, and how you respond to treatment.
  • Side effects caused by radiotherapy can be temporary or permanent.
  • Radiotherapy can be used alone or together with other cancer treatments to increase the chance of treatment success.

What is radiotherapy?

Radiotherapy, also known as radiation therapy, is an effective way to treat cancer. It uses focused radiation to kill or damage cancer cells so the cancer cannot grow or spread.

Different forms of radiotherapy use different kinds of radiation including:

  • x-rays — most often used
  • electron beams
  • gamma rays
  • proton beams

Radiotherapy is a localised cancer treatment. This means that it affects the part of your body being targeted.

Radiotherapy may be given together with other treatments, such as surgery and chemotherapy.

How does radiotherapy work?

Radiotherapy uses radiation — rays of very powerful energy — to kill or damage cancer cells. Radiotherapy can be used to treat many cancers.

Like other cancer treatments, radiotherapy can be used in different ways. This might be to:

  • achieve remission or cure
  • improve the effects of other treatments
  • relieve symptoms

Radiotherapy can be used before (neo-adjuvant), or after other cancer treatments (adjuvant), to make them more effective. This can help reduce the risk of your cancer coming back.

Radiotherapy can also be used palliatively. In this case it is used to decrease your pain or other cancer symptoms. It does this by making the cancer smaller or stopping it from spreading.


Chemoradiation is when both chemotherapy and radiation therapy are given together. This increases the success of the treatments as the chemotherapy drugs make the cancer cells more sensitive to radiation therapy.

Chemoradiation is only used to treat some cancers. These include:

Your medical team will plan your treatment to minimise damage to healthy cells near the cancer.

Your medical team will carefully consider the best way to deliver your radiotherapy. You may need to have a number of tests and scans so your doctors can plan your radiotherapy.

How is radiotherapy used?

Radiotherapy may be given:

  • from the outside — external beam
  • inside the body — brachytherapy

External beam radiotherapy (EBRT)

External beam radiotherapy is administered from outside your body. The radiation beams are produced by a large machine.

Before you start treatment, you will go to a planning session. This will help your doctors work out how to position you for treatment. Depending on the area being treated, you may use:

  • boards
  • wedges
  • beanbags
  • a special face mask

Your medical team will make sure you are in exactly the right position each time before starting the machine. This is so that the radiation is focussed on the cancer and not on your healthy tissues.

External beam radiotherapy does not hurt. During treatment the machine won't touch you, but you will hear some buzzing noises.

The actual radiotherapy usually only takes a few minutes.

Treatment is usually given on an outpatient basis, meaning that you can go home between sessions.

Sessions are often scheduled Monday to Friday, with a break over the weekend. You may need treatment for a number of weeks.

External radiation therapy does not make you radioactive because the radiation does not stay in your body.

Internal radiation therapy

Brachytherapy uses small radiation sources that are placed inside your body close to or inside the cancer. The devices are slightly smaller than a grain of rice. They produce gamma rays, a type of radiation that should kill the cancer cells.

Depending on the type of brachytherapy you are having, while the devices are inserted you may:

  • have a local anaesthetic to numb the area
  • have a general anaesthetic so that you're unconscious

One benefit of this treatment is that it can be given in a specific area — even deep inside your body — with minimal effects on healthy cells.

In some people, the radiation source is placed for a short time before being removed. In others, the radiation source is put in your body and left permanently.

Brachytherapy may be used alone or with external beam radiotherapy.

What are the side effects of radiotherapy?

Radiotherapy can treat many cancers but can also damage healthy cells close to the cancer cells being treated. This can lead to side effects.

The kinds of side effect you may experience, and how bad they are, can depend on:

  • your general health
  • the type and dose of radiation being given
  • the part of your body being treated
  • any other cancer treatments you may be receiving

Some people who have radiotherapy get very few side effects, while other people experience more side effects.

Usually, people get side effects from radiotherapy during or just after receiving treatment. Most side effects go away after treatment finishes. Sometimes radiation therapy can cause side effects months or years after treatment.

Common side effects include:

Many of these side effects can be treated and will get better over time.

Having radiation therapy near your reproductive organs can affect your fertility. This can be temporary or permanent.

Your medical team are very experienced in helping people who are receiving radiotherapy. They can give you information and support to manage any side effects.

How long will I need radiotherapy?

The length of your treatment will depend on many factors, including:

  • the type and stage of your cancer
  • how well the cancer responds to treatment
  • your ability to cope with the treatment and its side effects

You may have tests or scans after finishing therapy to see how the cancer responded to treatment. Radiotherapy continues to work for a while after treatment has ended. So, you may not know the full benefits of radiation therapy for a few months.

If your radiation therapy is palliative treatment, improvement in your symptoms is a good sign that the treatment is working.

Resources and support

Dealing with cancer and cancer treatment can feel overwhelming, but there are many organisations that can help with information and support. Visit:

To find out more about other cancer treatments, you can visit healthdirect's pages on:

If you want to know more about radiotherapy, you can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with 24 hours a day, 7 days a week.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: September 2023

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