Side effects of lung cancer radiotherapy

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 or so.

If you have had stereotactic radiotherapy, you might get side effects during treatment or up to 12 weeks after treatment.

These side effects vary from person to person. You may not have all of the effects mentioned.

Side effects can include:

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.

You might feel sick at times. You can have anti sickness medicines. Let your treatment team know if you still feel sick, as they can give you another type.   

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.

Radiotherapy to the chest area might cause some inflammation of your lungs. Soon after the treatment, you might have a dry cough or shortness of breath. This is called acute radiation pneumonitis (pronounced new-mon-eye-tiss).

Let your doctor or radiographer know if you feel breathless.

You might find that having a soft diet is easier to swallow until a few weeks after your treatment is over. Foods such as soups and stews are easier to swallow than more solid foods like meat or toast.

Your radiotherapy department can give you an information sheet to help advise you.

Tell your doctor or radiographers if you have problems swallowing. They can advise you on ways to reduce this.

Ask to see a dietitian if you have problems with eating and drinking.

Tips for eating and drinking
  • Drink about 8 glasses of water a day while having treatment.
  • Make sure that you eat slowly and avoid eating late in the day.
  • Drink plenty during and after meals to soften your food.
  • Eat small amounts often rather than big meals.
  • Try different foods to find out which are easiest to swallow.
  • You can have high calorie drinks to boost your calorie intake if you need them.

Your hair may fall out in the treatment area.

Some people may have mild chest discomfort, shivering and a raised temperature a few hours after treatment. This usually settles quickly.

If you had stereotactic radiotherapy, you might experience chest pain.

A painkiller such as paracetamol can help to relieve discomfort or pain.

Your appetite may vary during treatment. Try to eat well where possible and keep hydrated.

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.  

Rarely, your food pipe might become narrower and less stretchy over some months or years. This is called an oesophageal stricture. It can make it difficult for you to swallow.

If you develop a stricture, your doctor can stretch the food pipe slightly. They call this oesophageal dilatation. Stretching the food pipe opens it up again so that you can swallow food and drink more easily.

You have medicine to make you sleepy (sedation). Your doctor puts a tube called an endoscope down your throat. It has an area on it called a balloon. Your doctor expands the balloon to widen the food pipe. They repeat this a few times until the narrowing has gone. 

You might need to have this repeated if the narrowing happens again.

A cough and breathlessness happen in about 1 out of 25 people (4%) who have radiotherapy to the chest area. This is due to changes in the lung tissue called chronic radiation pneumonitis. It might start many months or a few years after treatment.

Let your doctor know if you notice any changes in your breathing or if you cough up a lot of mucus.

You might have regular tests to check how well your lungs work. Treatment with steroids or other medicines can help you to breathe more easily.

If your cancer is in the top of the lung, a group of nerves called the brachial plexus might receive some radiation. This group of nerves supply the arm. Your radiotherapy will be carefully planned to limit the dose to this area as much as possible.

Scarring of the lung in the treatment area could happen months to years after radiotherapy treatment.

Scarring is usually permanent and can cause a small portion of the lung to collapse. This might make you more short of breath, and you may need to use oxygen.

If your cancer is close to the ribs, radiotherapy may weaken the ribs, cause pain and cause ribs to break (fracture). This does not always cause any symptoms and may be found on a scan after your treatment.

Rarely the broken ribs can cause pain that requires painkillers for a long period of time.

Very rarely radiation can cause inflammation to the covering layer of your heart (pericardium). This is called pericarditis. It can cause:

  • chest pain that starts suddenly, often on the left side under your breastbone
  • tightness in your chest that gets worse when you lie down or breathe in

Very rarely lung radiotherapy can cause damage to your spinal cord.

Your doctor will talk to you about this possible side effect before you have treatment but it is extremely rare. 

Side effects if you have chemotherapy with radiotherapy

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

  • Lung cancer: diagnosis and management

    National Institute for Health and Care Excellence, 2019 (updated 22 September 2022)

  • Management of lung cancer
    Scottish Intercollegiate Guideline Network, 2014

  • A critical review of recent developments in radiotherapy for non-small cell lung cancer
    S Baker and others
    Radiation Oncology, 2016. 11:115

  • Hypofractionated Intensity-Modulated Radiotherapy for Patients With Non-Small-Cell Lung Cancer
    E Pollom and others
    Clinical Lung Cancer, 2016 Nov;17(6):588-594

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. If you need additional references for this information please contact with details of the particular risk or cause you are interested in.

Last reviewed: 
07 Feb 2023
Next review due: 
07 Feb 2026

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