Types of external beam radiotherapy

Ways of giving external beam radiotherapy

There are different ways of giving external radiotherapy. All the current ways of giving radiotherapy aim to reduce damage to healthy tissues and side effects. You might hear some of the following terms used by your health care team when they discuss your treatment with you.

Conformal radiotherapy

This uses a device inside the radiotherapy machine to shape the radiation beams to fit the treatment area.

Intensity-modulated radiotherapy (IMRT)

IMRT shapes the radiotherapy beam to a greater extent than conformal radiotherapy. It allows different doses of radiotherapy to be given to different parts of the treatment area. Tomotherapy® combines IMRT with a CT scan so each treatment is very accurate.

Image guided radiotherapy (IGRT)

IGRT makes sure that each treatment is targeted as accurately as possible. Images are taken just before or during a radiotherapy treatment. They are used to make adjustments to the treatment area, making it very precise.

Stereotactic ablative radiotherapy (SABR)

SABR allows large doses of radiotherapy to be given to small areas very precisely. It is used for some men with prostate cancer. There are different machines that can be used to give SABR. The linear accelerator (linac) that delivers standard radiotherapy can be used to give SABR. There are also specially designed linacs for SABR, which are known by their brand name, such as CyberKnife®. Because SABR treats smaller areas and is very accurate, fewer treatments (usually between 4–7) are needed. SABR is being evaluated in a trial to compare it to standard radiotherapy

Proton beam therapy

This uses a different type of radiation. It gives a very precise dose of radiotherapy to the prostate. It is not currently available in the UK. Trials haven’t shown any advantage over standard radiotherapy.


  • It may cure the prostate cancer.
  • It may prolong the life of men who have fast-growing cancers.
  • It is less invasive than having a prostatectomy.


  • It can cause erection problems and infertility.
  • For a small number of men it can also cause long-term bowel problems, such as loose or more frequent bowel motions, bleeding from the back passage or an altered bowel pattern.
  • A small number of men develop incontinence.
  • It may take some time before doctors know whether the treatment has been successful. They will check your PSA level to find out how successful the treatment has been. This should drop but it can take some time, depending on whether you have had radiotherapy on its own or with hormonal therapy. Ask your specialist for more information about this.
  • After radiotherapy you probably won’t be able to have surgery. This is because the scar tissue from radiotherapy makes surgery too difficult.
  • As the prostate gland is left in place, there is a possibility that prostate cancer may occur again in the prostate gland in the future.

Back to External beam radiotherapy explained

What is external beam radiotherapy?

External beam radiotherapy is the most common type of radiotherapy. A big machine directs external radiotherapy beams at the affected area.