Possible side effects of radiotherapy

Side effects may affect you no matter which area of the body you’re having radiotherapy to. It’s important to remember that most people will have a few side effects and they will often be mild. Most people only experience a few of the following:

  • tiredness
  • feeling sick
  • problems with eating and drinking
  • skin reactions
  • flu-like symptoms
  • hair loss
  • changes in your blood.

There are ways to help you manage side effects so they’re easier to cope with. If you need help and advice about dealing with any, speak to your doctor or radiotherapy staff. Most side effects last for about 10–15 days after treatment finishes.

Some people have side effects that last for longer, or develop some time after they have finished their treatment. These are called long-term or late effects.

Before you have radiotherapy, your clinical oncologist will talk to you about any likely side effects. You can ask the oncologist about any you’re particularly worried about.

Side effects of treatment

Radiotherapy affects people in different ways, so it’s difficult to predict exactly how you’ll react to your treatment. The side effects you have will depend on the type of treatment and the area of the body being treated.

Before you consent to your treatment, the hospital staff will talk to you about any side effects you may get. They will also give you tips on how to deal with them and how they can be treated.

External radiotherapy usually causes more general side effects than internal therapy. Here we discuss the general side effects of radiotherapy that you may experience, whichever part of the body you’re having radiotherapy to.

Before you start radiotherapy, you may also find it helpful to read more information about your type of cancer. It will include more information about the possible side effects of radiotherapy.

Modern treatments have reduced the frequency and severity of side effects. It’s important to remember that most people will have only a few of the side effects mentioned here.

Most side effects of radiotherapy will continue for about 10–15 days after treatment has finished and then gradually begin to get better. However, general tiredness may continue for longer.


Tiredness (fatigue)

Not everyone feels tired during radiotherapy treatment but many people do.

Tiredness can continue for weeks to months after your treatment has finished. It can often be made worse by having to travel to hospital each day, or by other treatments such as surgery or chemotherapy.

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

Managing tiredness

Get plenty of rest but balance this with some gentle exercise, such as short walks. This will give you more energy and help to keep your muscles working. Save some energy for doing the things you enjoy. You can also ask others for help doing chores if these are tiring you out.

We have more information about coping with tiredness (fatigue).


Feeling sick

Some people find that their treatment makes them feel sick (nausea), and sometimes they may actually be sick (vomit).

This is more likely to happen if the treatment area is near the stomach, or if the brain is being treated.

Your clinical oncologist (or sometimes a nurse or radiographer) can prescribe anti-sickness (anti-emetic) drugs if this happens. They may also prescribe them as a precaution. Tell your clinical oncologist or specialist radiographer if you have any nausea or vomiting, and remember that it usually stops once treatment is over.

Managing sickness

You may find it helpful to let someone else cook or prepare food for you, especially if the smell of cooking makes you feel sick. Sipping a fizzy drink slowly through a straw, drinking ginger tea, or eating crystalised ginger or ginger biscuits can also help.

If you’re given anti-sickness tablets, take them regularly, as this is the best way to control any sickness. Some anti-sickness medicines work best if you take them before your radiotherapy treatment. Ask your doctor, radiographer or nurse to tell you the best time to take your anti-sickness medicines.

We have more information to help you cope with feeling and being sick.


Problems with eating and drinking

During your treatment, it’s important to have a healthy diet and to drink plenty of fluids.

At times, you may not feel like eating, or you might find that your eating habits change. This may cause you to lose weight. If you can, it’s important to try to maintain your weight throughout treatment, as your radiotherapy will have been planned according to your body’s shape. Tell the radiotherapy staff if you’re having any problems with eating, as they may be able to arrange for you to talk to the hospital dietitian.

Some people who have radiotherapy to their head and neck area develop swallowing difficulties. If this happens to you, you may find it difficult to eat and drink until your swallowing improves.

If your oncologist thinks you may develop swallowing problems, they may suggest you have a small procedure to put a feeding tube into your stomach. We have more information about the different feeding systems your doctor might suggest.

Managing eating and drinking problems

Try having small, nutritious snacks throughout the day rather than large meals. If food seems tasteless, use seasoning or strong-flavoured sauces. If your mouth is dry, try sucking an ice cube. If you’re losing weight, add extra energy and protein to your diet with everyday foods or by using food supplements.

We have more information about managing eating problems. We also have recipes for people affected by cancer who are losing weight.


Skin reactions

You may develop a skin reaction while having external radiotherapy. If this happens, it usually begins after about 10 days.

How your skin reacts will vary depending on the amount of radiotherapy you have. Some people may find that the skin in the treatment area becomes red and sore or itchy. Or, it may become darker with a blue or black tinge. Sometimes the skin will get very sore and it may break and leak fluid, although this doesn’t happen very often. If your skin gets very sore, your treatment may have to be delayed for a short time to allow the area to recover, although this is very rare.

If you have a skin reaction, it will usually settle down 2–4 weeks after your treatment has finished. But the area may stay slightly darker than the surrounding skin.

Managing skin reactions

During your treatment, you will usually be advised to:

  • wear loose-fitting clothes made from natural fibres, such as a cotton T-shirt
  • wash your skin gently with soap, or aqueous cream, and water and gently pat it dry (aqueous cream should not be used as a moisturiser)
  • avoid rubbing the skin
  • avoid heating and cooling pads
  • avoid shaving, if possible
  • not use hair-removing creams or products, including wax
  • use a moisturiser that is sodium lauryl sulphate-free (your radiographer can give you more information about this)
  • use normal deodorant, unless your skin is broken
  • avoid the sun and use a high sun protection factor (SPF) sunscreen (your radiographer can give you more information about this).

If you develop a skin reaction such as soreness or a change in skin colour, let the radiotherapy staff know as soon as possible. They will advise you on the best way to manage it.

After your treatment has finished, you’ll need to protect the skin in the treated area from strong sunshine for at least a year.

Once any skin reaction has settled down, you should use a suncream with a high SPF of at least 30.

You should also wear close-weave clothing and a wide-brimmed hat if your head and neck area has been treated. It’s important to remember that you can burn through clothing if you’re 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 settled down. This is usually within a month of finishing treatment. Remember to use a waterproof suncream if you’re swimming outdoors.


Flu-like symptoms

If you have palliative radiotherapy given in one or two treatment sessions, you may experience flu-like symptoms. These include headaches, aching joints or muscles, and lack of energy (lethargy). If your temperature goes above 38°C (100.4°F), it’s important to let your radiotherapy team know.

Flu-like symptoms usually settle quickly. Drinking plenty of fluids and getting some rest can help.


Hair loss

Radiotherapy will only cause hair loss in the treatment area.

Hair loss can also happen where the radiation beam leaves the body (for example, on the back of the neck), 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 usually begins to fall out 2–3 weeks into radiotherapy treatment. It usually grows back after treatment finishes, but it may be a different texture or colour than before. It may take several months to grow back, although it depends on the dose of radiotherapy you have.

Occasionally, hair loss is permanent. Your doctor or radiographer can tell you if any hair loss is likely to be permanent.

Managing hair loss

If you lose the hair on your head, you may want to wear a wig to cover up your hair loss. Other ways of covering up hair loss include wearing a scarf or turban.

We have more information to help you cope with hair loss.


Changes in your blood

Radioisotope therapy, such as strontium or samarium, and sometimes external radiotherapy may temporarily reduce the number of normal red and white blood cells produced by the bone marrow (the spongy part inside some bones).

When the number of white blood cells is low, you’re more prone to infection. If necessary, you’ll be given antibiotics to treat any infection.

If the number of red blood cells is low (anaemia), you may get tired easily and may need a blood transfusion.

Your hospital team will arrange for you to have regular blood tests if the treatment you’re having is likely to cause your red blood cells to fall.

It’s very important to let your doctors know if you feel unwell, if your temperature goes above 38°C (100.4°F), or if you start feeling cold and shaky.


Effects on sexuality and fertility

Some women may have changes to the vagina and some men may have difficulty getting or keeping an erection. You may also experience changes in the physical and emotional feelings associated with sex. We have more information about how radiotherapy might affect your sex life.

We also have more information about the effect of radiotherapy on your fertility, for women and for men.


Long-term side effects of radiotherapy

All cancer treatments can result in long-term side effects. Modern ways of giving radiotherapy aim to limit the risk of permanent side effects. This has meant that the number of people who develop long-term problems is reducing. However, when radiotherapy is also given with chemotherapy, the long-term effects of radiotherapy may be increased.

Before you consent to the radiotherapy, your clinical oncologist will discuss the likelihood of you developing long-term side effects. It’s important that you have the opportunity to talk these through with your oncologist, even though they might not happen to you.

Not everyone has late effects. You can find more information about the possible long-term effects of treatment for your type of cancer.


Second cancers

Radiotherapy can cause cancer, and a small number of people will develop a second cancer because of the treatment they've had. However, the chance of a second cancer developing is so small that the risks of having radiotherapy are far outweighed by the benefits.

If you’re concerned about your risk of developing a second cancer, talk to your cancer specialist.

Back to Radiotherapy explained

What is radiotherapy?

Radiotherapy uses high-energy rays to destroy cancer cells. This treatment aims to treat cancer or relieve symptoms.

Making a radiotherapy mask

During radiotherapy to the head and neck a mask is used to help you keep still so that exactly the right area is treated.

Who might I meet?

You will meet many different specialists before, during and after radiotherapy treatment.

After treatment

It can take time to recover from radiotherapy. Support is there if you have any problems.