Possible side effects of radiotherapy

Your team plans your treatment carefully to reduce your risk of side effects. However, most people have a few side effects during or after radiotherapy.

Side effects do not usually happen straight away. They may develop during treatment or in the days or weeks after treatment finishes. Sometimes side effects get worse for a time after you have finished radiotherapy before they get better. There may also be a small risk of side effects that are long-term or that only start months or years after radiotherapy.

It is difficult to predict exactly how you will react to treatment. Your team will explain what to expect. Always tell them if you have side effects during or after radiotherapy. They can give advice and support to help you cope.

We have listed some general side effects of radiotherapy, but you are unlikely to get all of them. You may also get other side effects that we do not mention here. The side effects can depend on:

  • the area of your body being treated – you may find it helpful to read information about the cancer type you have
  • the type of radiotherapy you have
  • other treatments you are also having, such as chemotherapy.

We have separate information on possible effects on your sex life and fertility for men and women.

Tiredness

Not everyone feels tired during radiotherapy treatment, but many people do. Tiredness (fatigue) can continue for weeks or a few months after your treatment has finished. You might be more tired if you have to travel to hospital each day. Or you may also be having other treatments such as surgery or chemotherapy that make you more tired.

Some people are able to continue with their day-to-day activities, but others may find they need to rest more.

Problems with eating and drinking

At times during your treatment, you may not feel like eating. Or you may find that your eating habits change. Eating a healthy diet and drinking plenty of fluids is good for your general health. It helps your body cope with treatment. Tell your team if you are finding it difficult to eat.

Radiotherapy to some areas of the body can cause more serious side effects that may make eating and drinking difficult. This includes treatment to your head, neck or gullet (oesophagus). Your team may suggest that you have a feeding tube. The tube is usually put in before your treatment starts. You usually only need it for a short time. You can be fed through it if you have problems eating or drinking. When you can eat and drink again, it is taken out.

Coping with eating and drinking problems

Tell the radiotherapy team if you are having any problems. They can give you advice and may be able to arrange for you to see the hospital dietitian. The dietitian can monitor your weight and diet more closely.

We have more information about coping with eating and drinking problems.

Feeling sick

Some people find radiotherapy makes them feel sick (nausea) or be sick (vomit). This is more likely if the treatment area is near the stomach or the brain. Sickness can usually be well controlled and stops once treatment is finished. Your team may give you anti-sickness (anti-emetic) drugs to prevent nausea or vomiting.

Coping with feeling sick

Always tell your team if you have nausea or vomiting during or after your treatment. They can give you anti-sickness (anti-emetic) drugs or change the drugs you are taking. They will explain when and how to take the drugs. These drugs often work better when you take them regularly, or before you start to feel sick. Tell your team if the sickness does not improve.

Skin reactions

External beam radiotherapy can cause a skin reaction in the area being treated. If this happens, it usually begins after about 10 days.

You may find your skin in the treatment area becomes red or darkens. It may also feel sore or itchy. Sometimes the skin gets very sore and it may blister, break or leak fluid. Very rarely, your team may stop treatment for a short time to allow a serious skin reaction to recover.

Skin reactions can take time to improve. They are usually better about 4 weeks after your treatment has finished. The area of skin may always look or feel slightly different to the surrounding skin.

Coping with skin reactions

During your treatment, you are usually advised to:

  • wear loose-fitting clothes made from natural fibres, such as a cotton t-shirt
  • wash your skin gently with mild, unperfumed soap and water and gently pat it dry
  • avoid rubbing the skin
  • avoid heating and cooling pads
  • avoid wet shaving
  • avoid hair-removing creams or products, including wax
  • follow your team’s advice about using moisturisers and deodorants
  • avoid the sun (your radiographer can give you more information about this).

If your skin becomes sore or itchy or changes colour, let the radiotherapy team know as soon as possible. They can give you advice and treatments if needed.

When you finish radiotherapy, you should protect the skin in the treated area from strong sunshine for at least a year. Once any skin reaction has disappeared, use a suncream with a high SPF of at least 30. Wear close-weave clothing and a wide-brimmed hat to protect your head and neck area. Remember, you can burn through clothing if you are out in hot sun for a long time. Your radiographer can give you more information about this.

You can usually go swimming once any skin reaction has disappeared. Remember to use a waterproof suncream if you swim outdoors.

Hair loss

Radiotherapy only causes hair loss in the treatment area. You may lose your hair where the radiation beam leaves your body as well as where it enters the body. Ask your clinical oncologist or radiographer to show you exactly where your hair is likely to fall out.

Hair may start to fall out 2 or 3 weeks into radiotherapy treatment. It usually grows back after treatment finishes. Sometimes it grows back a different texture or colour than before. It may take several months to grow back, depending on the dose of radiotherapy you have.

Rarely, hair does not grow back or is patchy. Your doctor or radiographer can tell you if this is likely with your treatment.

If you are worried about losing the hair on your head, it may help to read our information about coping with hair loss.

Changes in your blood

Some treatments can reduce the number of normal blood cells produced by your bone marrow (the spongy part inside some bones). This includes some types of radioisotope therapy. Sometimes, it can also happen with external beam radiotherapy, especially if you have chemotherapy at the same time.

Your blood cell levels are unlikely to cause problems and they will improve after your treatment finishes. Some people need treatment if the level of certain types of blood cells is too low.

Your team will arrange any blood tests you need during and after your treatment. Always tell your team if you have any bruising or bleeding that you cannot explain. This includes:

  • nosebleeds
  • bleeding gums
  • tiny red or purple spots on the skin that may look like a rash.

You should also contact them straight away if:

  • your temperature goes over 37.5°C (99.5°F)
  • you suddenly feel unwell, even with a normal temperature
  • you have symptoms of an infection – this can include feeling shaky, a sore throat, a cough, diarrhoea or needing to pass urine a lot.

Late and long-term side effects of radiotherapy

After having radiotherapy, there is a small risk you will have side effects that:

  • do not get better after treatment – these are called long‑term side effects
  • only start months or years later – these are called late side effects.

This risk may be higher if you are also having other treatments, such as chemotherapy.

Before you decide to have cancer treatment, your team will explain your risk of developing these side effects. Even if it is not very likely, it is important that you understand and think about these long-term risks.

You can find more about possible long-term effects of radiotherapy in our information about the type of cancer you have. We also have information about the late effects of treatment for the following cancers:

Secondary cancers

Radiotherapy may increase your risk of developing a different type of cancer later in life. When this happens, it is called a secondary cancer.

The chance of developing a secondary cancer because of treatment with radiotherapy is small. This risk is far less than the benefits of treating the first cancer.

If you are worried about secondary cancer, talk to your cancer doctor.

How we can help

Macmillan Cancer Support Line
The Macmillan Support Line offers confidential support to people living with cancer and their loved ones. If you need to talk, we'll listen.
0808 808 00 00
Monday - Friday, 9am - 5pm
Email us
Get in touch via this form
Chat online
Monday - Friday, 9am - 5pm
Online Community
An anonymous network of people affected by cancer which is free to join. Share experiences, ask questions and talk to people who understand.
Help in your area
What's going on near you? Find out about support groups, where to get information and how to get involved with Macmillan where you live.