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Page last reviewed: 13/07/2011

Radiotherapy is used to treat conditions such as cancer, thyroid disorders and some blood disorders.

It is used to treat about 40% - 60% of people with cancer. The length of each course of radiotherapy depends on the size of the cancer and where it is on the body.

During radiotherapy, controlled doses of high-energy radiation, usually X-rays, destroy cancer cells in the affected area.

Uses of radiotherapy

Radiotherapy is used for a number of different medical purposes including:

  • to cure an illness, for example by destroying a tumour (abnormal tissue),
  • to control symptoms, such as relieving pain,
  • before surgery, to shrink a tumour so that it is easier to remove, and
  • after surgery, to destroy small amounts of tumour that may be left.

Radiotherapy is sometimes used in a process called total body irradiation (TBI). In severe cases of leukaemia (cancer of the bone marrow and white blood cells) or lymphoma (cancer of the lymphatic system), the whole body is given radiation to destroy the bone marrow cells.

After TBI, new bone marrow is transplanted. The new bone marrow is taken from a donor or from the patient before TBI.

This article focuses mainly on the use of radiotherapy to treat cancer.

Types of radiotherapy

Radiotherapy can be given in two ways:

  • External radiotherapy, where radiotherapy is given from outside the body using X-rays, electrons or, in rare cases, other particles such as protons.
  • Internal radiotherapy, where radiotherapy is given from within the body, either by drinking a liquid that is absorbed by the cancerous cells or by putting radioactive material into or close to the tumour.

Courses of radiation

Radiotherapy is often given as a course of treatment that lasts for days or weeks. Most people who have radiotherapy to treat a serious condition, such as cancer, receive five treatments a week: one treatment a day from Monday to Friday with a break at the weekend. This break allows the normal cells to recover. Each treatment is known as a fraction.


To reduce the side effects of a full dose of radiation, it is usually divided into smaller doses called fractions. You'll receive a fraction of radiation during each treatment session, which will equal the full dose by the end of the course.

Combination therapy

Radiotherapy is often used in combination with other treatments, such as chemotherapy (cancer-fighting medication). If surgery to remove a tumour is required, radiotherapy may be given alongside it.

Radiotherapy uses X-rays to treat disease. It is often used to treat cancer.
A dose is a measured quantity of a medicine to be taken at any one time.
A disease is an illness or condition that interferes with normal body functions.
Body tissue is a group of cells that perform a specific job, such as protecting the body from infection, producing movement or storing fat. 
Chemotherapy is the treatment of an illness or disease with a chemical substance. It is used to treat cancer.

Page last reviewed: 13/07/2011

Radiotherapy is used to treat and control many different types of cancer. It can also shrink a cancerous tumour (abnormal cell growth) before it is surgically removed. The aim of radiotherapy is to kill the cancerous cells in the affected area of the body.

Radiotherapy can be given externally or internally. External radiotherapy usually involves a course of treatment over days or weeks. Internal radiotherapy is usually given once or a small number of times.

External radiotherapy

External radiotherapy is given outside the body. A machine focuses high-energy X-rays, cobalt irradiation or other high-energy beams at the cancer. Surrounding healthy cells are also affected but are able to repair themselves following treatment.

If radiotherapy is recommended for you, you will be referred to a specialist radiotherapy department where you will receive your treatment. The type of machine used will depend on the reason for your treatment and the condition that you are being treated for, for example the type of cancer you have.

You will not feel any pain during the treatment, but you may later experience some pain or discomfort from the side effects of the treatment. Most side effects can be controlled and do not usually last long.

See Side effects, above, for more information.

Other types of external radiotherapy

As well as standard external radiotherapy, using X-rays or other high-energy sources, there are a number of other types of external radiotherapy.

Conformal radiotherapy

Conformal radiotherapy uses the same type of machine as standard external radiotherapy. However, metal blocks are put in front of the radiation beam, changing the shape of the beam so that it 'conforms' closely to the shape of the tumour.

This enables a higher dose of radiation to be used, increasing the chance of killing the cancerous cells. There is also a lower chance of long-term side effects because healthy tissue is affected less.

Intensity modulated radiotherapy

In intensity modulated radiotherapy (IMRT), computers control the shape and intensity of the radiation beams This allows very precise doses of radiation to be given to specific areas of the tumour. Before the procedure, a three-dimensional CT scan is taken to match the intensity of the dose with the shape of the tumour.

In IMRT, the cancerous tumour receives a very high dose of radiation while the surrounding healthy tissue receives a very low dose. As with conformal radiotherapy, side effects following treatment are likely to be lower than with standard external radiotherapy.

Internal radiotherapy

Internal radiotherapy uses radioactive materials (metals or liquids) to treat cancer. The two main types of internal radiotherapy are:

  • radioactive implants, and
  • radioactive liquids.

Radioactive implants

Radioactive implants are usually metal wires, seeds or tubes. They are inserted close to the cancerous tumour in a procedure known as brachytherapy.

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

Caesium and iridium are radioactive metals that are sometimes used to treat cancer of the cervix, womb and vagina.

Radioactive liquids

Radioactive liquids to treat cancer are given either as a drink or an injection. The radioactive part of the liquid is known as an 'isotope'.

Radioactive liquids include:

  • phosphorous, used to treat blood disorders,
  • strontium, used to treat secondary bone cancers, and
  • iodine, used to treat benign (non-malignant) thyroid conditions and thyroid cancer.


Health risks associated with radiotherapy are generally low because the amount of radiation used is usually very small. However, as internal radiotherapy involves placing radioactive substances inside your body, there are some safety issues you will need to discuss with your treatment team.

If you have a radioactive implant or radioactive liquid, your hospital will have a number of safety guidelines to ensure that hospital staff and visitors are not exposed to radiation. The hospital staff will explain the safety procedures to you before treatment.

Radioactive implants are inserted next to the cancerous tumour so that it gets the highest dose of radiation. The area that is close to the implant will also get a high dose of radiation.

Other parts of your body will receive a very small amount of radiation, which isn't a risk to your health.

Your body will give out a low level of radiation for a few days after having radioactive liquid. This gradually decreases as the radioactivity breaks down.

If you receive your radiotherapy treatment as an inpatient (you stay in hospital overnight), your treatment team can give you advice about visitors while you are in hospital and will ensure the radiation has decreased to a safe level before you are discharged.

See External links for more information about radiotherapy safety.

Page last reviewed: 13/07/2011

Following radiotherapy, it is likely you will have side effects. Side effects occur because radiotherapy damages some of your healthy cells as well as destroying the cancerous ones.

Side effects will depend on:

  • the part of your body being treated,
  • the dose of radiotherapy, and
  • how quickly the healthy cells are able to repair the damage.

Radiotherapy affects different people in different ways and it is difficult to know exactly how you will react to the treatment. Some people experience mild side effects but for others they are more severe.

Some side effects begin during treatment. Others can appear weeks or months afterwards. Before starting treatment, discuss the possible side effects with your treatment team.

Common side effects of radiotherapy

Common side effects of radiotherapy include:

  • tiredness,
  • nausea,
  • diarrhoea,
  • stiff joints and muscles,
  • dry mouth,
  • loss of appetite,
  • hair loss,
  • sore skin, and
  • a lack of interest in sex.


You will probably feel tired both during and after your radiotherapy treatment. Tiredness is particularly common towards the end of a course of treatment and can last for some time.

Tiredness usually occurs as a result of the body repairing the damage to healthy cells. It can also be caused by anaemia (a shortage of red blood cells) which is more commonly seen as a side-effect of chemotherapy.


Anaemia can develop if too many healthy red blood cells are destroyed during treatment, meaning less oxygen is carried around your body. During your treatment, you will have regular blood tests. If you have anaemia, you may need a blood transfusion.

Doing some gentle exercise may help relieve the symptoms of tiredness. Your doctor or treatment team can advise you about suitable exercise.


Some people feel sick at the start of their treatment. Others feel sick during it or for a short period of time after it has finished. If you are affected by nausea, your doctor or radiotherapist may be able to prescribe medication to control it.


Diarrhoea is a common side effect of radiotherapy to the abdomen (stomach) or pelvic area. It usually starts a few days after treatment begins and gradually gets worse as treatment continues.

After your treatment has finished, your diarrhoea should disappear within a few weeks.

Tell your doctor if you notice any blood in your stools (faeces). If your symptoms have not improved after a few weeks, tell your radiotherapist. They may refer you to a gastroenterologist (a specialist in stomach and bowel disorders).

Stiff joints and muscles

Sometimes radiotherapy can cause your muscles to tighten up and your joints to become stiff in the area being treated. You may experience some uncomfortable swelling in the affected area.

Exercising your joints and muscles regularly can help prevent stiffness. If you have stiff joints and muscles, your doctor or radiotherapist may refer you to a physiotherapist, who can recommend suitable exercises.

Loss of appetite

The combination of feeling sick and tired during radiotherapy can make you lose your appetite. You may have difficulty swallowing if you are having radiotherapy to your head, neck or chest.

If you have difficulty eating, you may find it easier to eat several small meals throughout the day, rather than a few larger meals. You can also speak to your radiotherapist who, if necessary, may refer you to a dietitian (nutritional specialist).

Sore skin

After external radiotherapy, your skin may become red and sore in the area being treated. Your treatment team can give you advice about the best way of caring for your skin during treatment.

If your skin becomes sore, try not to irritate it further. Avoid shaving and using perfumed soap in the affected area. Protect your skin from cold winds and wear a high-factor sunscreen (SPF 15 or above) to protect your skin from the sun.

Hair loss

Hair loss is another common side effect of radiotherapy. Many people find losing their hair stressful and difficult to cope with. Losing your hair can affect your confidence and may make you feel depressed.

Talk to your family and friends about how you are feeling so they can support you. After a few weeks of finishing treatment, your hair should start to grow back.

You may consider getting a synthetic (manmade) wig or a wig made from human hair.

Effects on sex and fertility in women

Having radiotherapy may cause you to lose interest in sex, particularly if you have other side effects such as tiredness or nausea or if you are anxious about your condition or treatment.

Radiotherapy to the vaginal area may cause your vagina to become narrower. Your radiotherapist will tell you how you can treat this using a vaginal dilator, a device that is inserted into your vagina to help prevent narrowing. Having sex regularly after your treatment can also help prevent your vagina narrowing.

If you experience vaginal dryness or pain when having sex, you can use lubricants, or ask your GP or radiotherapist to prescribe appropriate medication.

Radiotherapy directed at the pelvic area exposes the ovaries to radiation. In pre-menopausal women, this may cause early menopause and infertility (the inability to get pregnant). This is often very upsetting, particularly for younger women who want to have a family. Before your treatment, your radiotherapist will discuss all the options and available support with you.

For example, it may be possible for some of your eggs to be surgically removed, frozen and stored until you are ready to have a baby. T

Radiotherapy to other areas of the body will not affect your ovaries or make you infertile.

Effects on sex and fertility in men

In men, temporary impotence (the inability to get an erection) and loss of interest in sex are common side effects of radiotherapy. This is often caused by feeling tired after radiotherapy and being anxious about the treatment or illness.

Radiotherapy to the pelvic area can cause temporary or permanent impotence by affecting the nerves in and around your penis. Most other radiotherapy treatments will not make you infertile or cause any problems if you decide to have children in the future.

If there is a risk that you could become infertile, your radiotherapist will discuss this with you before your treatment.

Page last reviewed: 13/07/2011

Most side effects only last a few days or weeks after radiotherapy. However, some side effects, such as tiredness or hair loss, can last for a few months.

Follow-up appointments

After your radiotherapy has finished, you will have an appointment with your Radiation Oncologist to check on your progress. Follow-up appointments may continue for several years but will be less frequent as time goes on.

The timing of follow-up appointments will depend on whether you are having further treatment and whether or not the radiotherapy has been successful.

Your GP will be sent a report about your treatment and you will be able to contact a member of your treatment team if you have any questions or issues in between your follow-up appointments.

Effects of radiotherapy

The positive effects of radiotherapy usually take some time to show. Results depend on the condition you have and the stage it was at when treatment began.

The effectiveness of your treatment may depend on whether you are having other treatment alongside radiotherapy, such as chemotherapy or surgery.

See Useful links for more information about chemotherapy and follow-up appointments.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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