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Side effects of radiotherapy

Find out about the side effects of external radiotherapy to the lung and how to cope with them.

Side effects tend to start a few days 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 2 weeks or so.

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

Side effects can include:

You are likely to feel very tired during your treatment. It tends to get worse as the treatment goes on. You might also feel weak and lack energy.

After a while you might need to sleep after each radiotherapy session. 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: for example, exercise. Some research has shown that taking gentle exercise can give you more energy. It is 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 other medicines.   

Your skin might go red or darker in the treatment area. You may also get 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 also feel sore. Your radiographers will give you creams to soothe the skin. The soreness usually goes away within 2 to 4 weeks of ending the treatment. However your skin may be slighter darker in that area permanently.

Tell the radiotherapy staff if you notice any skin changes.

Your mouth and throat might get sore. It may be painful to swallow drinks or food. Let hot drinks cool before you drink them. You will have mouth washes to keep your mouth healthy.

You can have painkillers to reduce the soreness. Take them half an hour before meals to make eating easier.

Tell your doctor or nurse if your throat is sore.

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.

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.  

Side effects if you have chemotherapy with radiotherapy

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

Last reviewed: 
14 Sep 2017
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