Beating bowel cancer together


Radiotherapy is a possible treatment for rectal cancer, it is not usually used to treat bowel cancer. You may have radiotherapy to try to cure your cancer, either alone or together with surgery or chemotherapy (chemoradiation). If your cancer cannot be cured, you may have radiotherapy to relieve your symptoms. This is called palliative radiotherapy.

How is radiotherapy given?

External radiotherapy is delivered from outside of the body by a machine and only takes a few minutes. For this type of radiotherapy you will often need a specialist CT scan seven - 10 days before treatment to help plan how to give it.

Internal radiotherapy involves positioning radioactive sources inside or near to the tumour. Your healthcare team may offer you internal radiotherapy, depending on the size of the cancer and where it is in the rectum. The main advantage of this treatment is that it can deliver a high dose of radiation directly to the cancer while limiting damage to surrounding tissues and organs. This treatment, also known as brachytherapy or contact radiotherapy, is not currently available at all cancer centres, and you may have to travel to a specialist centre.

The Papillon technique is an example of contact radiotherapy for rectal cancer. It can be considered if the patient is not fit enough for anaesthetic or if the cancer is small and in its early stage. At the moment it is only available at a few specialist cancer centres. Your medical team will discuss this with you if it’s suitable for your cancer. You can find out more about Papillon technique here.

When is radiotherapy given? 

Before surgery

Radiotherapy can be given before surgery (also known as neo-adjuvant radiotherapy) to shrink the tumour in order to make it easier to remove and reduce the risk of the cancer coming back after your surgery. If you are prescribed external radiotherapy, the treatment could either be a short course (such as five days) or a long course (such as five treatments a week, for five or six weeks). The length of the treatment will depend on the size of your tumour. 

After surgery

Radiotherapy might also be given after surgery (also known as adjuvant radiotherapy) to reduce the chances of the cancer returning. The course of treatment will vary from five to six weeks. 

Palliative radiotherapy

If you have advanced cancer, radiotherapy may be given to help control symptoms. Speak to your doctor about what they are recommending for you, how the radiotherapy will be given and the choices you have. 


Radiotherapy together with chemotherapy (chemoradiation) shrinks the tumour, making it easier to remove. It also reduces the risk of cancer coming back in the same place, compared with radiotherapy alone. But chemoradiation causes more short term side effects, like diarrhoea.

If you didn’t have radiotherapy or chemotherapy before surgery, your specialist may offer you chemoradiation after surgery if there is a high risk of the cancer coming back.

Specialist radiotherapy techniques

Radiotherapy and other similar technologies can also be used in novel ways to treat bowel cancer that has spread to other parts of the body like the liver or lungs. These techniques can only be carried out in a few specialist centres around the UK, but they may offer some patients an alternative to surgery. There are a number of ways these new techniques are used, you may hear them referred to as IMRT (Cyberknife), stereotactic ablative radiotherapy (SABR) and radiofrequency ablation (RFA). Your healthcare team will be able to give you more information about these treatments if appropriate. 

Side effects

All treatments carry a risk of side effects. Your healthcare team should give you written information about the possible side effects. But they won’t be able to tell you in advance which side effects you will get or how long they will last.

If you are having radiotherapy and chemotherapy together, the side effects may be worse.

At your hospital appointments, your healthcare team will ask you about the side effects you’re getting. You might want to keep a diary to help you remember the details.

Possible short term side effects of radiotherapy include:

  • Bowel problems such as diarrhoea, constipation, wind, an urgent need to go to the toilet and abdominal cramps. Read more about regaining bowel control.
  • Bladder problems such as passing urine more often, burning and discomfort. It’s recommended you drink at least two – three litres of fluid a day and avoid drinking tea, coffee and alcohol
  • Sore skin
  • Sexual problems
  • Tiredness
  • Difficulty sleeping

These side effects often get better in the first few months after you finish treatment. But some people have long term or new side effects that do not get better without support from the healthcare team.

Possible long term side effects

You may have new or long term changes to the way your bowel works, such as loose and runny poo (diarrhoea), having to open your bowels more or less often than before, being woken from sleep to poo, having less warning to get to a toilet in time or being unable to control the bowel and having accidents.

Tell your healthcare team as soon as possible if you have any new or ongoing side effects. You may need to have some tests to find out what is causing them. Your healthcare team can give you treatments that can improve these side effects.

Radiotherapy may damage the bones in your pelvis (the area between your hips) and can lead to fractures. Tell your healthcare team if you have any pain or stiffness in your pelvis or back.

Radiotherapy can also irritate your bladder and can affect your sexual function.

Radiotherapy usually causes infertility. But you should still use contraception during treatment and for about a year afterwards in case there is any chance of pregnancy. Radiotherapy can damage sperm and eggs and harm a developing baby.

Many people living with bowel cancer worry about the cancer coming back and about returning to normal life after treatment. Your healthcare team can offer you support. Read our page on worries about the future for more information.

If you have any new symptoms or have any worries, speak to your healthcare team who can advise you where to find further information or support.

 Download our Your pathway booklet

More information

Macmillan Cancer Support has information on radiotherapy for rectal cancer and its side effects. Also for information on late effects of pelvic radiotherapy.

Cancer Research UK provides information on internal and external radiotherapy for rectal cancer.

Clatterbridge Cancer Centre gives information on Papillon technique, a special radiotherapy treatment

National Institute for Health and Care Excellence (NICE) provides patient information on high dose rate brachytherapy and low-energy contact X-ray brachytherapy.

Pelvic Radiation Disease Association is a patient-run charity providing support and information for people who have had pelvic radiotherapy.

Updated May 2019

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