Side effects of breast radiotherapy

Everyone is different and side effects can vary from person to person. You won't have all the side effects mentioned. Do talk to your healthcare team if you are worried about your side effects or have any questions.

Short term side effects

These can start after a couple of weeks of treatment. They continue to get worse during the treatment and after the treatment has finished. Generally these will start to get better a few weeks after treatment.

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. Putting a cool pad over the area may help. This will start to improve soon after your treatment has finished.

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

Your skin can also feel sore. Your radiographer will give you creams to soothe the skin. The soreness usually goes away within 2 to 4 weeks of ending the treatment. 

Towards the end of the radiotherapy, the skin might break down. especially under the breast. Your nurse will use special dressings to cover and protect the area. The area usually heals up over a couple of weeks.

Tell the radiotherapy staff 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 lymphoedema.

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 armpit

Your hair might fall out in the area under the arm (armpit) on the treated side. 

You might also lose hair anywhere within the treatment area. 

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 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.

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.

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 a swelling in the arm called lymphoedema after radiotherapy or surgery to the armpit. 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.

The British Association of Skin Camouflage can also help.

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 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 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 may need replacing. 

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 area, 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.

Bone problems

Radiotherapy can make the bones in the treated area become weaker after many years. This can cause pain and can also increase the risk of fractures.

Your doctor or nurse can check your bone strength with a bone density Open a glossary item (DEXA) scan if needed. Tell them if you have any pain in your shoulder or ribs.

Nerve damage around the treatment area

Scaring 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.

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 usually 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.

Last reviewed: 
02 Feb 2021
Next review due: 
02 Feb 2024
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