Radiotherpay is a treatment where raditation is used to kill cancer cells.

When radiotherapy is used

Radiotherapy may be used in the early stages of cancer or after it has started to spread.

It can be used to:

  • try to cure cancer completely (curative radiotherapy)
  • make other treatments more effective - for example, it can be combined with chemotherapy (chemoradiation) or used before surgery (neo-adjuvant radiotherapy)
  • reduce the risk of cancer coming back after surgery (adjuvant radiotherapy)
  • releive symptoms if a cure isn't possible (palliative radiotherapy)

Types of radiotherapy

Radiotherapy can be given in several ways.  Your doctors will recommend the best type for you.

The most common types are:

  • radiotherapy given by a machine (external radiotherapy) - where a machine is used to carefully aim beams of radiaiton at the cancer
  • radiotherapy implants (brachytherapy) - where small pieces of radioactive metal are (usually temporarily) placed inside your body near the cancer
  • radiotherapy injections, capsules or drinks (radioisotope therapy) - where radioactive liquid is swallowed or injected into your blood
  • intrabeam radiotherapy, where radiation is delivered directly at the tumour during breast cancer surgery (this treatment is not available at all NHS hospitals)

Radiotherapy is usually given in hospital. You can usually go home soon after external radiotherapy, but you may need to stay in hospital for a few days if you have implants or radioisotope therapy.

Read more about what happens during radiotherapy.

Side effects of radiotherapy

As well as killing cancer cells, radiotherapy can damage some healthy cells in the area being treated.

This can cause some side effects, such as:

  • sore skin that might change colour to red, lighter or darker than your usual skin tone
  • feeling tired
  • hair loss in the area being treated
  • feelign sick
  • losing your appetite
  • a sore mouth
  • diarrhoea

Many of those side effects can be treated or prevented and most will pass after the treatment stops.

External radiotherapy doesn't make you radioactive, as the radiation passes through your body.

The radiation from implants or injections can stay in your body for a few days, so you may need to stay in hospital and avoid close contact with other people for a few days as a precaution.

You may need to avoid close contact with children and pregnant women when you go home for a short time. Your care team will let you know what to do.

How is it performed?

Radiotherapy can be carried out in many different ways, depending on your circumstances.

Before treatment starts

Deciding to have treatment

If you're diagnosed with cancer, you'll be cared for by a team of specialists. Your team will recommend radiotherapy if they think it's the best option for you, but the final decision is yours.

Making this decision can be difficult. You may find it useful to write a list of questions to ask your care team.

For example, you may want to find out:

  • what the aim of treatment is – for example, is it being used to cure your cancer, relieve your symptoms or make other treatments more effective?
  • about possible side effects and what can be done to prevent or relieve them
  • how effective radiotherapy is likely to be
  • whether any other treatments could be tried instead

If you agree with your team's recommendation, they'll start to plan your treatment once you've given your consent to treatment.

Planning your treatment

Your treatment will be carefully planned to ensure the highest possible dose is delivered to the cancer, while avoiding damage to nearby healthy cells as much as possible.

You will probably have a computerised tomography (CT) scan to work out exactly where your cancer is and how big it is.

After the scan, some very small but permanent ink marks may be made on your skin to ensure the right area is targeted accurately each time.

If you're having radiotherapy to your head or neck, a plastic mask will be made for you to wear during treatment. The ink marks will be made on the mask.

Your treatment 

Before treatment starts, your care team will draw up a plan that outlines:

  • the type of radiotherapy you'll have
  • how many treatment sessions you'll need
  • how often you'll need treatment

Some people have five treatments each week (one treatment a day from Monday to Friday, with a break at the weekend). But sometimes treatment may be given more than once a day or over the weekend.

Your doctor may call each dose a "fraction", although the term "attendance" is sometimes used to indicate how many hospitals visits you'll need to make during treatment.

If radiotherapy is being used to control your symptoms, you may only need a single session

Want to know more?

How radiotherapy is given

Radiotherapy can be given as:

  • external radiotherapy – where a machine directs beams of radiation at the cancer
  • a radioactive implant inside your body near the cancer
  • a radioactive liquid that you swallow or have injected
  • directly at the tumour during surgery (intrabeam radiotherapy)

Externl radiotherapy

During external radiotherapy, you lie down on a table and a machine is used to direct beams of radiation at the cancer.

The machine is operated from outside the room, but you'll be watched through a window or a camera. There will be an intercom if you need to speak to the person treating you.

You need to keep as still as possible throughout the treatment. It usually only takes a few minutes and is completely painless. You can normally go home soon after it has finished.

Radiotherapy implants (brachytherapy)

Radioactive implants (metal wires, seeds or tubes) may be used to treat cancer in areas of the body where they can be placed inside the body without surgery (such as the vagina).

Sometimes surgery is used to place an implant near the cancer.

The length of time the implant is left in your body varies. It could be a few minutes or a few days. In some cases, tiny implants may be left inside the body permanently.

The radiation from the implants is painless, but it could be harmful to others so you may need to stay in hospital for a few days until the implant is removed.

Permanent implants aren't a risk to others because they produce a very small amount of radiation that gradually decreases over time.

But you may need to avoid close contact with children and pregnant women for a short time as a precaution. Your care team will let you know what to do.

Radiotherapy injections, capsules or drinks (radioisotope therapy)

Some types of cancer, including thyroid cancer and some prostate cancers, can be treated with radioactive liquid that's swallowed or injected.

You may be radioactive for a few days after treatment is given, so you'll probably need to stay in hospital as a precaution until the amount of radiation has fallen to a safe level.

Your treatment team may give you some advice to follow for a few days when you get home to avoid putting other people at risk.

Intrabeam radiotherapy

This is where radiotherapy is delivered directly at the tumour during breast cancer surgery.

This treatment is not available at every NHS hospital, only those with an intrabeam machine.

Want to know more?

Issues during treatment

Pregnancy and contraception

Women should avoid becoming pregnant while having radiotherapy, as the treatment could harm your baby.

Rarely, it may be possible to have radiotherapy in pregnancy. But this depends on where in your body you are having treatment

Use an effective method of contraception, such as a condom, and contact your care team immediately if you think you may be pregnant.

Men having radiotherapy may sometimes be advised to use contraception during treatment and possibly for several months afterwards.

Macmillan has more information about sex life and radiotherapy.

Side effects

Radiotherapy can cause a range of side effects.

Read about the side effects of radiotherapy.

Deciding to stop treatment

Some people decide that the benefits of radiotherapy aren't worth the poor quality of life, due to the side effects.

If you're struggling with the treatment and are having doubts about whether to continue, it's a good idea to speak to your care team.

Your team can give you advice about the likely benefits of continuing with treatment, but the final decision to continue or stop is yours.

Side effects

Radiotherapy can cause side effects, although many of these can be treated or prevented and most will pass once treatment stops.

It's difficult to predict what side effects you'll get and in some cases you may only develop side effects months, or even years, after you start treatment.

Side effects vary from person to person and depend on things such as the part of your body being treated and the type of radiotherapy you have. Ask your care team about the side effects you might get.

Sore skin

In some people, radiotherapy can make your skin sore, change colour (it might become red, lighter or darker than your normal skin tone), or dry and itchy. Sometimes it can blister and peel.

This tends to start 1 to 2 weeks after treatment begins.

Tell your care team if you notice any soreness or changes to your skin.

To care for your skin during radiotherapy you should:

  • wash your skin every day with your usual soap
  • pat your skin dry instead of rubbing it
  • apply your usual moisturiser every day, or start using a moisturiser
  • use your usual deodorant, unless it irritates your skin
  • avoid shaving the area if possible and do not use laser, wax, or hair-removal creams
  • avoid using heat or cold packs on the area
  • try wearing loose-fitting clothes made from natural fibres such as cotton or silk, and avoid tight bands, ties or straps on the sore area
  • use a high-factor sunscreen (SPF 50 or above) to protect your skin from the sun and continue to use it for at least a year after treatment ends
  • check with your care team if you should stop swimming – chlorine in the water can sometimes make your skin worse when you're having radiotherapy
  • stop using any products on your skin if your skin breaks

Skin problems usually settle within 2 to 4 weeks of treatment finishing, but sometimes your skin might stay slightly darker or lighter than it was before.


Many people having radiotherapy feel tired a lot of the time or tire very easily doing everyday activities.

This usually starts during treatment and can continue for several weeks or months after treatment finishes.

It can help to:

  • get plenty of rest
  • avoid doing tasks or activities that you don't feel up to
  • do light exercise, such as going for short walks, if you're able to – this can boost your energy levels, but be careful not to push yourself too hard
  • ask your friends and family for help with everyday tasks

If you're working, you may want to ask your employer for time off or to let you work part-time until your treatment has finished.

Contact your care team if you suddenly feel very tired and out of breath. This can be a sign of a lack of red blood cells (anaemia), which may need to be treated.

Hair loss

Hair loss is a common side effect of radiotherapy. But unlike chemotherapy, it only causes hair loss in the area being treated.

Ask your care team to show you exactly where your hair is likely to fall out.

Your hair will usually start to fall out two to three weeks after treatment starts.

It should start to grow back a few weeks after treatment finishes, although sometimes it may be a slightly different texture or colour than it was before.

Occasionally, hair loss can be permanent if you have a high dose of radiotherapy. Ask your doctor if this is a risk before starting treatment.

Coping with hair loss

Hair loss can be upsetting. Talk to your care team if you find losing your hair difficult to cope with.

They understand how distressing it can be and can support you and discuss your options with you.

You may decide you want to wear a wig if you lose the hair on your head. Synthetic wigs are available free of charge on the NHS for some people, but you'll usually have to pay for a wig made from real hair.

Other options include headwear such as headscarves.

Feeling sick

Some people feel sick during, or for a short time after, radiotherapy treatment sessions.

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

Tell your care team if you feel sick during or after treatment. They can prescribe anti-sickness medication to help.

You should stop feeling sick soon after your treatment finishes.

Macmillan has more information about managing sickness and vomiting.

Problems eating and drinking

Radiotherapy can sometimes cause:

  • a sore mouth
  • loss of appetite and weight loss
  • discomfort when swallowing

Sore mouth

Radiotherapy to the head or neck can make the lining of the mouth sore and irritated. This is known as mucositis.

Symptoms tend to develop within a couple of weeks of treatment starting and can include:

  • the inside of your mouth feeling sore – as if you've burnt it by eating very hot food
  • mouth ulcers, which can become infected
  • discomfort when eating, drinking and/or talking
  • a dry mouth
  • reduced sense of taste
  • bad breath

Tell your care team if you have any of these problems. They may recommend painkillers or special mouthwashes that can help. Avoiding spicy, salty or sharp foods can also help.

Mucositis usually clears up a few weeks after treatment finishes, although sometimes a dry mouth can be a long-term problem.

Loss of appetite

Feeling sick and tired during radiotherapy can make you lose your appetite, which could lead to weight loss.

But it's important to try to eat healthily and maintain your weight during treatment, so tell your care team if you don't feel you're eating enough.

They may give you tips such as eating frequent small meals instead of three large ones or refer you to a dietitian.

Discomfort when swallowing

Radiotherapy to the chest can irritate the gullet (oesophagus), which can temporarily make swallowing uncomfortable.

Tell your care team if this affects you, as you may need to make some changes to your diet (such as eating soft or liquid foods).

You may also be prescribed medication to reduce the discomfort and in a few cases you may need a temporary feeding tube.

Swallowing problems will usually improve after treatment stops.


Diarrhoea is a common side effect of radiotherapy to the tummy or pelvic area.

It usually starts a few days after treatment begins and may get a bit worse as treatment continues.

Tell your care team if you get diarrhoea. Medication is available to help relieve it.

Diarrhoea should disappear within a few weeks of treatment finishing. Tell your doctor if your symptoms haven't improved after a few weeks, or if you notice blood in your poo.

Stiff joints and muscles

Radiotherapy can sometimes makes the joints and muscles in the area being treated stiff, swollen and uncomfortable.

Exercising and stretching regularly can help to prevent stiffness.

Tell your care team if it's a problem. They may refer you to a physiotherapist, who can recommend exercises for you to try.

Sex and fertility issues

Radiotherapy can have an effect on your sex life and fertility, especially if your lower tummy, pelvic area or groin is treated.

Ask your care team if there's a chance it could affect you.

Sex and fertility issues for women

In women, there's a risk that radiotherapy could cause:

  • loss of interest in sex( loss of libido) – this tends to gradually improve after treatment stops
  • stiffening and narrowing of the vagina – your care team may suggest using vaginal dilators (devices you insert into your vagina) to prevent this; having sex regularly may also help
  • vaginal dryness – lubricants, vaginal moisturisers and medicated creams can help with this
  • the menopause – this can cause symptoms such as hot flushes and night sweats, but treatment with hormone replacement therapy (HRT) can help
  • infertility – if there's a risk this could happen, it may be possible to store some of your eggs before treatment

Cancer Research UK has more information about women's sex life and fertility after radiotherapy.

Sex and fertility issues for men

In men, there's a risk that radiotherapy could cause:

  • loss of interest in sex – this tends to gradually improve after treatment stops
  • difficulty getting an erection (erectile dysfunction) – this tends to improve with time and there are several erectile dysfunction treatments available
  • pain when ejaculating – this should pass a few weeks after the treatment ends
  • infertility – if there's a risk this could happen, it may be possible to store a sample of your sperm before treatment

Cancer Research UK has more information about men's sex life and fertility after radiotherapy.

Emotional issues

Having radiotherapy can be a frustrating, stressful and traumatic experience. It's natural to feel anxious and to wonder if your treatment will be successful.

Stress and anxiety can also increase your risk of getting depression.

Speak to your care team if you're struggling to cope emotionally. They can offer support and discuss possible treatment strategies.

Joining a cancer support group may also help. Talking to other people in a similar situation can often reduce feelings of isolation and stress.

The charity Macmillan Cancer Support has a directory of support groups. You can also call the Macmillan Support Line free on 0808 808 00 00  every day, 8am to 8pm


Radiotherapy can damage your body's lymphatic system, a network of channels and glands that form part of your immune system (the body's defence against illness).

One of the jobs of the lymphatic system is to stop fluid building up in your body. If it becomes damaged, you may experience pain and swelling. This is known as lymphoedema.

It's most common in the arms or legs, but it can affect other areas, depending on the part of your body that was treated.

It may be possible to reduce your risk of lymphoedema by looking after your skin and doing regular exercises. Ask your care team if you're at risk and what you can do to help avoid it.

If you do get it, treatment for lymphoedema can often help keep the symptoms under control.

Getting another type of cancer

Radiotherapy can slightly increase your risk of developing another type of cancer in the years after treatment.

But the chance of this happening is small and the benefits of treatment generally outweigh the risk.


The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website
Last Updated: 03/08/2023 12:24:25