Side effects of radiotherapy for rectal cancer

Side effects tend to start a week after the radiotherapy begins. They gradually get worse during the treatment and for a couple of weeks after the treatment ends. But they usually begin to improve after around 2 weeks.

The side effects vary from person to person. You might not have all of the following side effects. 

Tiredness and weakness

You might feel tired during your treatment. It tends to get worse as the treatment goes on. You might also feel weak and lack energy. Rest when you need to.

Tiredness can carry on for some weeks after the treatment has ended. But it usually improves gradually.

Various things can help you to reduce tiredness and cope with it, such as exercise. Some research has shown that taking gentle exercise can give you more energy. It's important to balance exercise with resting.

Sore skin

The skin around your anus and back passage (rectum) is very sensitive. Radiotherapy can make it red and sore. 

Tips

  • Wash your skin with tepid water and simple soaps.
  • Pat your skin dry with a soft towel.
  • Ask your doctor, nurse or radiographer for creams to protect your skin and help it heal quickly.
  • Don't use perfumed or medicated soaps and lotions.
  • Try using a soft cushion if you have difficulty sitting comfortably for a while.

After your treatment is over, the soreness should gradually get better over a few weeks. 

Diarrhoea

Tell your doctor, nurse or radiographer if you have diarrhoea. They can prescribe medicine to help you. 

Drink plenty of fluids. This helps to keep you hydrated. 

Ask your nurse about soothing creams to apply around your back passage (rectum). The skin in that area can get very sore and even break if you have severe diarrhoea.

An inflamed bladder (radiation cystitis)

For a while after having the treatment you might feel that you have to pass urine more often than usual. And you may have a burning feeling when you do. Or you might feel that you can’t wait then you need to go. This is called cystitis.

The treatment temporarily inflames the lining of your bladder. It helps to drink plenty of fluids. You might find that some drinks increase the soreness, such as tea and coffee. You can experiment for yourself and see what works for you. 

Tell your doctor or nurse if you have bladder soreness. They can prescribe medicines to help.

'Just can’t wait' card

You can get a card to show to staff in shops or pubs. It allows you to use their toilets without them asking awkward questions. You can get the cards from Disability Rights UK or the Bladder and Bowel Community. They also have a map of all the public toilets in the UK.

Disability Rights UK can also give you a key for disabled access toilets so that you don't have to ask for a key when you are out.

Long term side effects

Most side effects gradually go away in the weeks or months after treatment. But some side effects can continue or might start some months or years later.  

Side effects if you have chemotherapy with radiotherapy

Chemotherapy combined with radiotherapy can make some side effects worse. Combining these treatments is called chemoradiotherapy.

  • Rectal cancer: ESMO Clinical Practical Guidelines for diagnosis, treatment and follow up
    R Glynne-Jones and others
    Annals of Oncology, 2017. Volume 28, Pages 422-440

  • Image Guided Radiotherapy (IGRT) Guidance for implementation and use
    National Radiotherapy Implementation Group Report, August 2012

  • Principles and practice of oncology (11th edition)
    VT De Vita, S Hellman and SA Rosenberg
    Wolters Kluwer, 2019

Last reviewed: 
25 Feb 2022
Next review due: 
25 Feb 2025

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