Side effects of breast radiotherapy

Radiotherapy for breast cancer can cause side effects such as swelling and difficulty moving your arm and shoulder. Everyone is different and side effects can vary from person to person. You may only have very few side effects, or you may have several.

Talk to your healthcare team if you are worried about your side effects or have any questions.

Short term side effects

These can start during treatment and continue to get worse while you are having treatment. They usually continue for about 2 to 4 weeks after your treatment has finished but then begin to improve. 

Short term side effects of breast radiotherapy include:

  • tiredness and weakness
  • skin problems
  • swelling of the breast
  • loss of hair in the treatment area 
  • problems moving your arm and shoulder
  • feeling or being sick

Tiredness and weakness

You might feel tired during your radiotherapy 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.

Skin problems

Sometimes the skin feels tender or sensitive to touch. If this happens do let your therapy radiographer Open a glossary item or specialist nurse know.

Your skin might go red or darker than normal in the treatment area, your neck, shoulder and your back. Your skin might always be slightly darker in these areas.

Your skin can also feel sore. Your radiographer will give you advice and may give you some creams to soothe the skin. 

Towards the end of the radiotherapy, the skin might break down, especially under the breast. Your nurse or radiographer may give you some creams and a special dressing to cover and protect the area. The area usually heals over a couple of weeks.

Your skin usually starts to improve 3 to 4 weeks after treatment. Tell the radiotherapy staff or breast care nurse if you notice any skin changes.

Swelling of the breast

Radiotherapy can make it more difficult for fluid to drain from the breast tissue. This can cause swelling of the breast or chest area. Doctors call this lymphedema or oedema of the breast.

The swelling usually goes down a few weeks after the treatment ends. But tell your doctor or radiographers if it doesn’t. They can arrange for you to see a lymphoedema specialist. You might have a type of massage called manual lymphatic drainage.

Loss of hair in the treatment area

You might lose hair anywhere within the treatment area. The most common place is in the area under the arm (armpit) on the treatment side. 

You may have hair loss in other areas depending on where you are having treatment. For example, you may have hair loss on your head if you are having radiotherapy to the brain for secondary breast cancer Open a glossary item.

This can happen about 10 days after your treatment starts. It may take weeks or months to grow back. For some people, it may never grow back.

Problems moving your arm and shoulder

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

It’s important to continue the arm exercise you were shown after your surgery. This will make it easier for you to lift your arm to the correct position during radiotherapy. It can also help stop your arm and shoulder from becoming stiff.

Feeling or being sick

Radiotherapy can make you feel sick, especially if you are having treatment in your tummy (abdomen) or brain. If this happens, your treatment team can give you anti sickness medicines to help you. Take them 20 to 60 minutes before having radiotherapy. 

General side effects of radiotherapy

This video talks about some of the general side effects of radiotherapy. It lasts around 8 minutes.  

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.

Most of these side effects are rare. You might get one or two of them. There are things you can do to deal with any side effects that you have. 

A swollen arm

Some people get swelling in the arm called lymphoedema after radiotherapy or surgery to the lymph nodes. You can help to prevent this swelling and if it happens there are treatments to control it.

Skin changes

The treatment area might look permanently tanned after your treatment has finished. This is not harmful.

Later, you might appear to have very tiny broken veins in the skin called telangiectasia.

You can cover up any skin changes with camouflage make up. Your GP can prescribe it.
There are different colours for all skin tones. Some clinical nurse specialists are trained in showing you how to apply it.

Your consultant or GP can refer you to the skin camouflage service run by Changing Faces. This free service teaches you how to apply the make up and creams. It can also advise you on the best products to buy.

Changes in the shape, size, and feel of the breast 

In time radiotherapy can cause the breast tissue to change shape or shrink in size a little. This can happen to your natural breast tissue or a reconstructed breast. 

After radiotherapy, the skin on the breast might feel thicker. And the breast might feel hard and less stretchy. This is due to a side effect called radiation fibrosis.

Sometimes the breast can shrink a little over time. This is because radiotherapy can make the breast tissue contract so that the breast gradually gets smaller.

An implant in a reconstructed breast can become hard (capsular contracture) and painful. The implant may need more surgery to correct or replace it. 

Let your surgeon know of any changes, they may be able to do some minor surgical adjustments to improve the look.

Breathing problems

A cough and breathlessness happen in some people who have radiotherapy to the chest and lymph node areas, but this is not common. The problems are due to changes in the lung tissue called chronic radiation pneumonitis. They 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.

Heart problems

Many years after radiotherapy to the left breast, some people might have changes to their heart. But this is rare.

Your treatment team can explain this risk to you. 

Bone problems

Radiotherapy can make the bones in the treated area become weaker after many years. For some people, this doesn't cause any problems. For others, it can cause pain and increase the risk of rib fractures.

Nerve damage around the treatment area

Scarring from radiotherapy may cause nerve damage in the arm on the treated side. This can develop many years after your treatment. Symptoms include tingling, numbness, pain, and weakness. In some people, it may cause some loss of movement in the arm and shoulder.

This side effect is rare. Speak to your doctor if you notice any of these symptoms. 

Other cancers 

Radiotherapy treatment may cause another type of cancer in many years’ time. These are rare, your doctor will talk to you about these risks.

If you have side effects

Let your doctor or nurse know if you have side effects or are worried about anything. 

When treatment ends you might have regular appointments for about 5 years afterwards. You can talk to your doctor or nurse at these appointments. But you don't have to wait for your next appointment if you get a new side effect or are worried about anything. You can bring the appointment forward.

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    F Cardoso and others
    Annals of Oncology, 2019. Volume 30, Issue 8, Pages 1194–1220

  • Estimating the risks of breast cancer radiotherapy: evidence from modern radiation doses to the lungs and heart from previous randomised trials 
    C Taylor and others
    Journal of Clinical Oncology, 2017. Vol 35, issue 15. pages 1641-1649

  • Postoperative radiotherapy for Breast Cancer: UK consensus statement

    The Royal College of Radiologists, 2016. Last updated 2019

  • Cancer: Principles and Practice of Oncology (12th edition)
    VT DeVita, TS Lawrence, SA Rosenberg
    Wolters Kluwer, 2023

  • 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. Please contact with details of the particular issue you are interested in if you need additional references for this information.

Last reviewed: 
06 Jul 2023
Next review due: 
06 Jul 2026

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