Chest radiotherapy side effects

Chest radiotherapy includes radiotherapy to your breast, your chest wall (if you've had surgery to remove your breast) or to your chest itself. This can include radiotherapy to the lungs or to the food pipe (oesophagus). Side effects will depend on where you're having treatment to.

The main side effects from chest radiotherapy include:

  • difficulty swallowing
  • sickness
  • weight loss
  • breathlessness
  • lymphoedema Open a glossary item after breast cancer treatment
  • breast changes and problems moving your arm and shoulder
  • heart problems

You may also experience more general side effects of radiotherapy such as sore skin and tiredness.

Like all side effects of radiotherapy, you might not feel these straight away. Side effects tend to come on gradually as you go through your treatment. And for a few weeks afterwards. Everyone reacts differently to radiotherapy, so how you feel varies from person to person. 

Difficulty swallowing

Radiotherapy to the chest might cause swelling and soreness in the oesophagus and you might have difficulty swallowing. Difficulty swallowing is also called dysphagia. This side effect usually starts with a feeling of a lump in the throat.

Whether you have problems swallowing depends on:

  • where exactly you are having treatment
  • if your throat or oesophagus is in the radiotherapy treatment area
  • the amount of radiation you have

Difficulty swallowing may be worse and can last longer if you have chemotherapy at the same time as radiotherapy.

Let your healthcare team know as soon as swallowing becomes uncomfortable. They can give you medicines to help.

You may see a Speech and Language Therapist (SLT) before you start treatment if this is likely to affect your swallowing. An SLT can assess your swallowing during and after treatment. They can teach exercises to support you with swallowing difficulties. And they work with a dietitian if you are finding it difficult to eat. You usually see a dietitian weekly during treatment.

Occasionally, if you can’t swallow at all, you will have a temporary feeding tube. This means having a tube down your nose or through your skin into your stomach or small bowel.


Radiotherapy to the chest can make you feel or be sick. This is called nausea and vomiting. The sickness might last for a few weeks after the treatment has finished. Medicines, diet and sometimes complementary therapies can help to control sickness.

Sickness can usually be well controlled with medicines. Your radiotherapy doctor can prescribe anti sickness tablets for you to take. Some people find that it helps to take an anti sickness tablet about 20 to 60 minutes before having treatment.

Other people find they manage better by taking anti sickness tablets regularly throughout the day during their course of treatment. You can discuss which would be best for you with your radiotherapy team.

Weight loss

Radiotherapy to your chest area can make you lose weight. This is because you may have difficulty swallowing and feel sick, which can cause a poor appetite.

These effects might be temporary and gradually go back to normal after treatment ends. But for some people, the effects may be permanent.

It's important to maintain your weight for radiotherapy treatment. Your radiotherapy is planned very precisely using your body measurements. This means if you lose or gain weight during radiotherapy it can change the amount of radiation that the cancer or nearby healthy cells receive. Losing too much weight might also make you feel weaker.

During your radiotherapy treatment:

  • you might see a dietitian once a week who can help to advise you on foods that are easier to eat
  • your doctor or dietitian may give you nutritional supplements, such as high calorie drinks to help keep your weight up
  • your doctor might prescribe strong painkillers if you have pain when swallowing
  • try not to drink alcohol (especially spirits) or smoke because this can make your mouth and throat very sore

If eating becomes very difficult you might have a feeding tube put into your stomach through your skin. Or a liquid feed through a drip.

Breathlessness or cough

Having radiotherapy to the chest, for example for lung cancer, can cause shortness of breath during and after radiotherapy. Shortness of breath will usually improve a few weeks after treatment but for some people it can continue long term.

Short term effects of radiotherapy to the chest

You may notice:

  • a cough that can sometimes get worse once your treatment has finished
  • a small amount of blood in your sputum
  • coughing up fresh blood, which rarely could be life threatening

If you have any unusual bleeding, you must report this to your healthcare team straight away.

Your specialist will discuss this all with you before you start treatment. If you are worried, let your healthcare team know.

Radiotherapy to the chest causes inflammation of the lungs, which is called acute radiation pneumonitis (pronounced new-mon-eye-tiss). This can make you feel more breathless. Always let your doctor, radiographer or nurse know if you are short of breath. They may give you some medicines for this. This condition should improve a few weeks after treatment.

Rarely shortness of breath might be because of a more serious condition, such as a chest infection or a blood clot in the lung. In rare circumstances, this may need urgent assessment and could become life threatening without any treatment.

Long term effects of radiotherapy to the chest

After having radiotherapy to the chest there is a risk of chronic radiation pneumonitis. It causes a long term cough and sometimes breathlessness.

Let your doctor or nurse know if you notice changes in your breathing any time after your radiotherapy. It might be possible to learn breathing exercises or use medicine that can help to reduce your breathlessness. But in some rare cases breathing problems may be permanent.

Before starting treatment, you need to tell your radiotherapy doctors if you have a heart condition that makes you breathless or if you have a heart pacemaker. Radiotherapy can make heart conditions worse over many years for some people.

Lymphoedema after breast cancer treatment

Breast cancer treatment can cause a build up of lymph fluid in the breast, chest or arm. This is called lymphoedema. It is pronounced lim-fo-dee-ma.

The lymphatic system carries clear watery fluid called lymph, which drains out from the small blood vessels (capillaries) into the body tissues. Cancer or cancer treatment can affect the fluid drainage channels of the lymphatic system. Fluid then doesn't drain in the normal way, so the area swells.

About 1 in 5 people (20%) will have lymphoedema of the arm after breast cancer treatment that includes:

  • surgery to remove lymph nodes
  • radiotherapy to the lymph nodes

If lymphoedema is not treated, it may get worse. It can be painful and make it difficult to move your arm.

Before you start treatment, your doctor will talk to you about:

  • your risk of developing lymphoedema
  • what you can do to reduce the risk of lymphoedema developing
  • what to do if you notice any swelling

Treatment aims to reduce the swelling and stop the fluid from building up again.

Breast changes and problems moving your arm and shoulder

Radiotherapy to the breast can cause breast changes and problems moving your arm or shoulder.

After radiotherapy, the breast might feel hard and less stretchy. This is due to a side effect called radiation fibrosis. This side effect is usually mild. Sometimes the breast can shrink over time. This is because radiotherapy can make the breast tissue contract so that the breast gradually gets smaller.

Radiotherapy might make it harder to move your arm and shoulder. This can affect your activities and work. It usually improves when the treatment finishes. Your nurse or physiotherapist can give you exercises to help.

Heart problems

Radiotherapy to the left side of your chest might mean your heart receives a small amount of radiation. This is because the heart is on the left side. This can cause some side effects.

The heart is sensitive to radiation. You might be at a higher risk if you have heart problems or have had them in the past. You must tell your doctor if you have a pacemaker.

Radiotherapy is more accurate than it has ever been so the chance of your heart receiving radiation is much lower. Also if you're having radiotherapy to the left side you might be asked to hold your breath at certain points during treatment. This is so that the heart is moved out of the radiation treatment area. This is called deep inspiration breath hold (DIBH) treatment.

Radiotherapy is also carefully planned so that if the heart has to be in the treatment area, only a small part of it will be.

The risk of heart side effects depends on how much treatment you're having and the type of radiotherapy.

The main side effect is pericardial effusion. This is when fluid builds up around the heart. This can cause breathlessness. If this happens, you may need a procedure to drain the fluid.

This video shows people affected by cancer talking about the side effects of radiotherapy to the chest. The video is around 5 and a half minutes long.

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Last reviewed: 
24 Feb 2024
Next review due: 
24 May 2027

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