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

There are many different ways you can have radiotherapy, but they all work in a similar way.

They damage cancer cells and stop them from growing or spreading in the body.

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)

Radiotherapy is generally considered the most effective cancer treatment after surgery, but how well it works varies from person to person.

Ask your doctors about the chances of treatent being successful for you.

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

Treatment is usually given in hospital.  You can normally 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.

Most people have several treatment sessions, which are typically spread over the course of a few weeks.

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, red skin
  • feeling tired most of the time
  • 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.

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How is it performed?

Radiotherapy can be administered in a number of ways. The treatment recommended for you will depend on your individual circumstances.

If radiotherapy is recommended, you'll be referred to a specialist radiotherapy department for treatment.

Your treatment team will discuss possible side effects of radiotherapy with you and you 'll be asked to sign a consent form to confirm you agree to the treatment and understand any risks involved.

Planning your treatment

Your treatment will be carefully planned to ensure the highest possible dose is delivered to the tumour (to maximise the effectiveness of the treatment) while minimising the dose to surrounding healthy tissues.

Your treatment plan depends on:

  • where the cancer is in your body
  • the type and size of the cancer
  • your general state of health

In planning your treatment, your doctor (a radiotherapy specialist or clinical oncologist) will use all the information gathered during your diagnosis. They may also carry out some additional tests to find more about the size and site of the cancer and get a clearer understanding of the area of your body to be treated.

Once your oncologist has all the relevant information, they'll calculate the total dose of radiotherapy you need and the number of individual doses required.


If you're having external radiotherapy (see below), a simulator machine may be used as part of your treatment planning. The simulator moves in the same way as the machine used for your treatment. It uses X-rays to take pictures so your treatment team knows how to position your body when you have treatment.

Most patients have a CT scan to help the oncologist target the tumour accurately. After the scan, the radiographer may put small but permanent ink marks on your skin to ensure the treatment area is targeted accurately each time.

If you're having external radiotherapy to your head or neck, or if it's difficult for you to keep the part of your body having treatment still, a plastic mould will be made for you to wear during treatment. In this case, the ink markings will be made on the mould rather than on your skin.

You can read more about planning external radiotherapy on the Cancer Research UK website.

Courses of treatment

Radiotherapy is usually given as a number of individual treatments delivering a small dose of radiation daily over several weeks.

Most people have five treatments a week (one treatment a day from Monday to Friday), with a break at the weekend. However, in some cases treatment may be given more than once a day or over the weekend.

The course of treatment usually lasts between one and seven weeks.

The individual radiotherapy doses are often called "fractions". However, the term "attendances" may be used to indicate how many hospitals visits will be needed during treatment. This term is sometimes preferred because it's possible to have several treatment fractions during one hospital visit.

The number of fractions or attendances required depends on the type of cancer being treated and the aim of treatment. If radiotherapy is used to relieve symptoms, rather than cure the cancer, fewer sessions are usually needed.

External beam radiotherapy

External beam radiotherapy can be delivered using a variety of techniques.

Conventional external beam radiotherapy

Most people receiving radiotherapy have external radiotherapy delivered by a source of radiation outside the body.

External radiotherapy is usually carried out as an outpatient procedure, so you won't have to stay in hospital overnight. However, you may need to stay in hospital if you're having chemotherapy in combination with radiotherapy (chemoradiotherapy), or if you're unwell.

During the procedure, you'll be positioned on a treatment table and a radiotherapy machine (usually a machine called a linear accelerator) directs high-energy radiation at the area being treated.

You'll need to keep as still as possible throughout the treatment, although you can breathe normally. The procedure only takes a few minutes each day and is completely painless.

While you're having treatment, you'll be left alone in the treatment room. A radiographer operates the machine from outside the room and watches you through a window or on closed circuit television. If necessary, you'll be able to talk to the radiographer during the procedure using an intercom.

Intensity-modulated radiation therapy (IMRT)

Intensity-modulated radiation therapy (IMRT) is an advanced type of radiation therapy used to treat cancer and noncancerous tumours. IMRT uses computer technology to manipulate multiple small radiation beams of varying intensities to precisely conform to the shape of a tumour. The radiation intensity of each beam is controlled, and the beam shape changes throughout each treatment.

The goal of IMRT is to distribute the radiation dose to maximize the dose delivered to the tumour while avoiding or minimising exposure of healthy tissue to limit the side effects of treatment.

Image-guided radiation therapy (IGRT)

Image-guided radiation therapy (IGRT) uses a variety of advanced imaging techniques throughout the course of radiotherapy to accurately identify, pinpoint and monitor your tumour for changes. IGRT allows your oncologist to modify the treatment beams during treatment, which increases the chances of the treatment being effective.

Stereotactic radiosurgery (SRS)

Stereotactic radiosurgery (SRS), sometimes known as Gamma Knife radiosurgery, is a highly precise radiation therapy used to treat tumours and other abnormalities in the brain.

Specialised equipment focuses up to 200 tiny beams of radiation to deliver a high dose to the treatment area, usually in one treatment in a single day. During the procedure, your head is placed in a frame to keep it still. The accuracy of SRS results in minimal damage to healthy tissues.

Stereotactic body radiation therapy (SBRT)

Stereotactic body radiation therapy (SBRT) can be delivered on some modern linear accelerators or with a CyberKnife machine.

CyberKnife treatment involves using a small linear accelerator mounted on a mobile arm. This allows multiple radiation beams to be directed at any part of the body from any direction to deliver a high radiation dose to the tumour and, at the same time, limit damage to healthy tissue.

Internal radiotherapy

Sometimes a source of radiation inside the body is used to deliver internal radiotherapy.

Internal radiotherapy can involve a radioactive implant, drink or injection. Depending on the type of treatment being used, you may need to stay in hospital for a short period of time. Radiation emitted by internal radiotherapy is painless, though the procedure to insert the source can sometimes cause mild discomfort.

Radioactive implants

The use of radioactive implants (known as brachytherapy) usually involves the insertion of metal wires, seeds or tubes near the cancerous cells.

These implants are often used to treat areas of the body where an implant can be placed inside the body without surgery. For example, a radioactive implant can be placed in the vagina to treat cervical cancer. In some cases, surgery is used to place an implant near the cancerous cells.

The length of time the radioactive implant is left inside your body depends on the type and nature of your cancer. It could be a few minutes or a few days. In some cases, tiny radioactive implants may be left inside the body permanently.

If you're having a radioactive implant, you may need to stay in hospital for a few days until the radioactive source is removed. After the implant has been removed, you're not a risk to others.

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

Liquid radiotherapy

Liquid radiotherapy involves the use of radioactive liquids, usually to treat thyroid cancer. These can be given either as a drink, an injection into a vein, or an injection directly into the area affected by cancer.

After having liquid radiotherapy, you may be radioactive for a few days. This won't cause any long-term harm to your body, but you'll probably have to stay in hospital as a precautionary measure until the radioactivity decreases.

The radiation dose will be carefully monitored and you'll be able to leave hospital after the radiation has fallen to a safe level. Your treatment team may give you some safety advice to follow for a few days when you get home.

If there's anything about your treatment you don't understand, or if there's anything you're unsure about, you should ask a member of your treatment team to explain it to you in more detail.

You can read more about internal radiotherapy safety on the Cancer Research UK website.

Follow-up appointments

After your course of radiotherapy has finished, you'll have an appointment with your oncologist to check on your progress. The first appointment is often between four and six weeks after treatment finishes.

You may need follow-up appointments for several years, but they'll usually become less frequent as time passes.

Your GP will be sent a report about your treatment. You'll also be able to contact a member of your treatment team if you have any questions after your course of radiotherapy has finished.

How is radiotherapy given

Radiotherapy is usually given in one of two ways:

  • external radiotherapy – where a machine directs beams of radiation at the cancer
  • internal radiotherapy – where a radioactive implant is placed inside your body near the cancer, or a radioactive liquid is swallowed or injected

The main types of radiotherapy are outlined below.

Radiotherapy given using a machine (external 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.

Sometimes a slightly different technique may be used, such as:

  • intensity-modulated radiation therapy (IMRT) – where the shape and strength of the radiation beams are varied to closely fit the area of the cancer
  • image-guided radiation therapy (IGRT) – where scans are done before and during each treatment session to ensure the cancer is targeted accurately
  • stereotactic radiosurgery (SRS) – where lots of tiny beams of radiation are aimed at the cancer very precisely, so a high dose can be given at once (usually in a single treatment)
  • stereotactic body radiation therapy (SBRT) – where several beams of radiation are directed at the cancer from several directions

You can ask your doctor about the technique being used for your treatment.

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.

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.

Want to know more?

Issues during treatment

During radiotherapy treatment, there are a number of important things to bear in mind.

Pregnancy and contraception

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

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.

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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.

It varies from person to person and depends 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.

Some of the main side effects are listed below, but it's unlikely you'll have all of these.

Sore skin

In some people, radiotherapy can make the skin sore and red (similar to sunburn), darker than normal or dry and itchy.

This tends to start a week or two after treatment begins.

Tell your care team if you notice any soreness or changes to your skin. They may suggest:

  • washing your skin every day with mild, unperfumed soap
  • patting your skin dry instead of rubbing it
  • moisturising your skin every day
  • not using perfume, perfumed soaps or talcum powder on the area
  • not shaving the area if possible – if you need to shave, use an electric razor instead of wet shaving
  • wearing loose-fitting clothes made of natural fibres, and avoid tight collars, ties or shoulder straps
  • using a high-factor sunscreen (SPF 15 or above) to protect your skin from the sun
  • not swimming in chlorinated water

Skin problems usually settle within two to four weeks of treatment finishing, but sometimes your skin may stay slightly darker (like it's tanned) 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 – 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 (Monday to Friday 9am-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.

Talk to your care team if you're concerned about the risk of developing another type of cancer in the future.

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The information on this page has been adapted by NHS Wales from original content supplied by NHS Choices.
Last Updated: 26/07/2017 15:20:55