Side effects of radiotherapy

Radiotherapy can cause general side effects as well as more specific ones. Specific side effects depend on where your soft tissue sarcoma is in your body.  

For many people, the side effects of radiotherapy wear off within a few weeks of the treatment ending. But for some, radiotherapy can cause long term side effects.

Everyone is different and the side effects vary from person to person. You may not have all the effects mentioned below.

General side effects

Hair loss happens in the treatment area. You will only have hair loss from your head if you are having radiotherapy to your head. You may lose body hair in the treatment area – for example, leg hair if your leg is being treated. 

The hair may grow back but sometimes doesn't. If it does grow back, it can take up to a year and it may be patchy. Whether the hair grows back and how long it takes depends on the amount of treatment you have had.

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.

Your skin might go red or darker in the treatment area. You might also get slight redness or darkening on the other side of your body. This is where the radiotherapy beams leave the body. 

The red or darker areas can feel sore. This may start after your radiotherapy treatment is completed. Your radiographers may give you creams to soothe your skin. The soreness usually goes away within 2 to 4 weeks of ending the treatment. But your skin might always be slightly darker in that area.

Tell the radiotherapy staff if you notice any skin changes.

Specific side effects

Radiotherapy may cause specific side effects depending on which part of the body is treated. 

You may feel sick or have diarrhoea. Or you may have some abdominal pain or bladder irritation.

Radiotherapy to the head and neck can cause:

  • a sore dry mouth
  • thickened saliva
  • difficulty in swallowing
  • changes in taste
  • feeling sick

Possible long term 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. 

Radiotherapy treatment to a joint, such as a knee or elbow, can make it stiff by causing hardening of tissues (fibrosis) in the treatment area.

It is important to keep using the joint as normally as you can. Regular exercise will help you to be able to keep moving the joint and stop it from stiffening up.

Months or years after radiotherapy, some people develop lymphoedema. Lymphoedema is swelling in the area close to where the radiotherapy was given. The radiotherapy damages the small tubes that circulate tissue fluid around the body (the lymphatic vessels). Fluid builds up behind the blockage and causes swelling in the tissues. 

Doctors plan radiotherapy carefully to minimise the risk of lymphoedema developing. They now try to prevent it by leaving a column of untreated tissue along your arm or leg. So, they don't treat your arm or leg all the way round. If you do get swelling in your hand or foot after radiotherapy to that limb, tell your specialist. 

Lymphoedema can't be cured. But there is treatment to control lymphoedema. The earlier it is diagnosed, the easier it is to control.


People who have treatment to the pelvic area or top of the thighs may become unable to have children (infertile) due to the effects of treatment on the testes, or ovaries and womb. This can be very upsetting.

Women can sometimes have ovarian transposition. This is a surgery that moves your ovaries out of the field of radiation. Doing this will lower the amount of radiation your ovaries are exposed to during the radiotherapy. It helps the ovaries to keep working properly after treatment.

Another option is egg harvesting, but this might delay treatment.

Men may be able to store sperm in a sperm bank before they have treatment.

Bowel and bladder changes

Pelvic radiotherapy can also cause: 

  • changes in the bowel, such as diarrhoea and wanting to poo more urgently and frequently
  • irritation of the bladder or leakage of urine

Pelvic radiotherapy for woman can have side effects such as vaginal dryness and tightening. The vaginal wall tissue can become tighter and thicken.

Women are normally referred to a gynaecology oncology clinical nurse specialist. They can teach you how to use vaginal dilators. Dilators stretch the vaginal tissue. The vagina can become less stretchy and narrower due to scar tissue that forms. This can have an effect on your sex life.

Side effects usually settle down a few weeks after treatment has finished in most people. Talk to your doctor if you continue to have problems, or if they appear some time after treatment.

  • UK guidelines for the management of soft tissue sarcomas
    A Dangoor and others
    Clinical Sarcoma Research, 2016. Volume 6, number 20 

  • Technical Basis of Radiation Therapy: Practical Clinical Applications
    SH Levitt
    Springer Science & Business Media, 2012

  • Radiation therapy techniques in cancer treatment

    T Mitin and others

    UpToDate website

    Accessed July 2021

  • Radiotherapy side effects: integrating a survivorship clinical lens to better serve patients

    V Dilalla and others

    Current oncology, 2020, 27(2), 107–112

Last reviewed: 
23 Jul 2021
Next review due: 
23 Jul 2024

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