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Radiotherapy, also known as radiation treatment, is the controlled use of high energy X-rays to treat many different types of cancer. About  4 out of 10 people with cancer have radiotherapy.

In some cases, radiotherapy can also be used to treat benign (non-cancerous) tumours.

The length of each course of radiotherapy will depend on the size and type of cancer and where it is in the body.

Uses of radiotherapy

Radiotherapy may be used:

  • To cure an illness - for example, by destroying a tumour (abnormal tissue)
  • To control symptoms - for example, to relieve pain
  • Before surgery - to shrink a tumour to make it easier to remove
  • After surgery - to destroy small amounts of tumour that may be left

Radiotherapy is sometimes used to treat thyroid disease, as well as some blood disorders and other benign conditions. This topic focuses mainly on the use of radiotherapy as a treatment for cancer.

Types of radiotherapy

Radiotherapy can be given in two ways. It can be given from:

  • Outside the body (external radiotherapy) – using X-rays, small particles called electrons or, in rare cases, other particles such as protons; external radiotherapy is usually given once a day as a course of treatment over a number of days or weeks
  • Within the body (internal radiotherapy, also known as brachytherapy) – either by drinking a liquid that is absorbed by the cancerous cells or by putting radioactive material into, or close to, the tumour, usually for a small number of treatments (brachytherapy) or by injecting or drinking a liquid that is absorbed by the cancerous cells – for example, radioiodine for thyroid cancer

Courses of radiation

Radiotherapy is usually given as a course of treatment that lasts for a number of days or weeks.

Most people who have radiotherapy to treat a serious condition, such as cancer, have five treatments a week (one treatment a day, Monday to Friday) with a break at the weekend. Taking a break allows the normal, non-cancerous cells to recover.

In some cases, treatment may be given more than once a day or over the weekend.


Radiation treatment is divided into a number of small doses called fractions, which are usually given over a number of weeks. Fractions are used to reduce the side effects of a full dose of radiation. The number of fractions required will depend on the type of cancer being treated.

Combination therapy

Radiotherapy is often used in combination with other treatments, such as chemotherapy (powerful medication that is used to treat cancer). This is known as chemoradiotherapy.

Chemoradiotherapy can be used to try to cure a cancerous tumour, to shrink a tumour before it is removed using surgery, or after surgery to reduce the risk of relapse.

How radiotherapy works 

External radiotherapy

During external radiotherapy, a machine called a linear accelerator focuses high-energy X-rays or other high-energy beams at the cancer. Radiation kills the cancerous cells but also causes temporary damage to healthy, non-cancerous cells, resulting in side effects, most of which are temporary because normal tissues are able to repair themselves.
If radiotherapy is recommended, you will be referred to a specialist radiotherapy (oncology) department where you will receive your treatment. The type of machine that is used will depend on the reason for your treatment and the condition that you are being treated for.

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

Internal radiotherapy

Internal radiotherapy uses radioactive materials (metal implants or liquids) to treat cancer. The two types of radioactive material are described below.

Radioactive implants (brachytherapy)

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

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

Radioactive metals, such as caesium and iridium, are sometimes used to treat prostate cancer, cancer of the womb, cervical cancer and vaginal cancer. 

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 - which is used to treat blood disorders
  • Strontium - which is used to treat secondary bone cancers
  • Iodine - which is used to treat benign (non-cancerous) thyroid conditions and thyroid cancer


Health risks associated with radiotherapy are usually minimal because the radiation dose received by the rest of the body is usually very low. 

However, as internal radiotherapy involves placing radioactive substances inside your body, there are some safety issues that you will need to discuss with your treatment team.

How radiotherapy is performed 

Radiotherapy is only used if the benefits outweigh the risks. Your treatment team will discuss the risks of any radiotherapy procedures that are recommended for you.

Before having radiotherapy, you will be asked to sign a consent form to confirm that you agree to the treatment and understand any risks involved.

Treatment plan

Your treatment will be carefully planned to ensure that the radiotherapy destroys as many cancerous cells as possible, while affecting as few healthy cells as possible.

The amount of radiotherapy you have will depend on:

  • Where the cancer is in your body
  • The type and size of the cancer
  • Your general state of health

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

Once your oncologist has all the relevant information, they will calculate the total dose of radiotherapy that you need and the number of individual doses (fractions) required.

If you are having external radiotherapy, a simulator machine will be used as part of your treatment planning. The simulator moves in the same way as the machine that will be used for your treatment. It uses X-rays to take pictures so that the radiographer knows how to position your body when you have your treatment. A radiographer is a healthcare professional who is trained in taking X-rays.

Many patients will also have a computerised tomography scan (CT) scan to help the oncologist to target their tumour accurately.

After the exact area of your body to be treated has been established, the radiographer will put small but permanent ink marks on your skin to ensure that the same area is treated each time.

If you are having external radiotherapy to your head or neck, or if it is 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.

External radiotherapy

If you are having external radiotherapy, you will usually receive your treatment as an outpatient, which means that you will not have to stay in hospital overnight. You may need to stay in hospital if you are having chemotherapy in combination with radiotherapy (chemoradiotherapy), or if you are unwell.

During the procedure, you will be positioned on a treatment table and a radiotherapy machine (linear accelerator) will direct high-energy rays at the area being treated.

You will need to keep as still as possible throughout the treatment. The procedure only takes a few minutes and is completely painless. You will be able to breathe normally during your treatment.

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

Internal radiotherapy

Internal radiotherapy can be given as an 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.

Radioactive implants

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

Radioactive implants are placed into, or next to, the cancerous tumour so that it gets the highest possible dose of radiation. Although the area 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 is not a risk to your health.

If you are 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 are not a risk to others.

Permanent implants do not present a risk because they produce a very small amount of radiation that gradually decreases over time.

Liquid radiotherapy

After having liquid radiotherapy, you may be radioactive for a few days. This will not cause any long-term harm to your body, but you will probably have to stay in hospital until the radioactivity decreases. This is a precautionary measure to reduce other people’s exposure to radiation.

You will be able to leave hospital after the radiation has fallen to a safe level. Dr. B C Shah may give you some safety advice to follow for a few days when you get home.

If there is anything about your treatment that you do not understand, or if there is anything you are unsure about, you should ask a member of your treatment team to explain  it to you in more detail.

Common side effects of radiotherapy 

Following radiotherapy, it is highly likely that you will have some side effects. Side effects occur because radiotherapy temporarily damages some of the 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
  • 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 following radiotherapy, while others experience more severe effects. Some side effects begin during treatment whereas others can appear weeks or months afterwards.

Before starting treatment, you should discuss the possible side effects with your treatment team.

Common side effects of radiotherapy include:

  • Sore skin
  • Tiredness
  • Feeling sick
  • Dry mouth
  • Loss of appetite
  • Diarrhoea
  • Dair loss
  • discomfort on swallowing
  • a lack of interest in sex
  • stiff joints and muscles

These are explained in more detail below.

Sore skin

Your skin may become red and sore in the area being treated towards the end of a course of radiotherapy, or for a couple of weeks afterwards.

Depending on the area being treated, and the individual’s reaction to radiation, some people’s skin may peel after having a course of radiotherapy. This usually heals within a couple of weeks.

Dr. B C Shah will be able to give you advice about the best way of caring for your skin during treatment. If your skin becomes sore, you should try not to irritate it further.

You should 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.


You will probably feel tired both during and after having radiotherapy. Doing some gentle exercise may help to relieve the symptoms of tiredness.

Tiredness is particularly common towards the end of a course of radiotherapy and it can last for some time afterwards. It usually occurs as a result of the body repairing the damage to healthy cells.

A shortage of red blood cells (anaemia) can also contribute to tiredness during radiotherapy.

For some cancers, regular blood tests may be required during radiotherapy to ensure that you are not becoming anaemic. If you have anaemia, you may need to have a blood transfusion (where you receive blood that is removed from another person who is known as a donor).

Feeling sick (nausea)

Most people are not sick during radiotherapy. However, some people feel sick (are nauseated) at the start of, during, or for a short time after, their treatment. If you experience  nausea, your doctor may be able to prescribe medication to help control it.

Radiotherapy to your abdomen (tummy area) or pelvic area may make you sick. This can last a few days after your treatment stops. Again, medication or complementary therapies can help.

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 may refer you to a dietitian (nutritional specialist).


Diarrhoea is a common side effect of radiotherapy to the abdomen or pelvic area. It usually starts a few days after treatment begins and gradually gets worse as treatment continues. You should tell your doctor if you notice any blood in your stools (faeces).

After your treatment has finished, diarrhoea should disappear within a few weeks. You should tell your doctor if your symptoms have not improved after a few weeks.

Hair loss

Hair loss is a common side effect of radiotherapy to your head or neck. Radiotherapy will only cause hair loss in the area being treated.

Many people find losing their hair stressful and difficult to cope with. Losing your hair can affect your self-confidence and it may make you feel depressed.

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

You may consider getting a synthetic (man-made) wig or a wig that is made from human hair. 

  • Inpatients (those who need to stay in hospital overnight for treatment)
  • Those under 16 years of age
  • Those between 16 and 19 years of age who are in full-time education

Discomfort on swallowing

Radiotherapy to the chest can cause the tube through which food passes (the oesophagus) to become temporarily inflamed, which may cause temporary discomfort when swallowing. If required, Dr. B C Shah will be able to prescribe medication to help soothe your throat.

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.

You should avoid eating hot or spicy food and drinking acidic drinks or spirits during this time because they can aggravate the problem.

Radiotherapy to the vaginal area may cause your vagina to become sore and narrower. Your radiotherapist will tell you how you can treat this using a vaginal dilator, which is a device that is inserted into your vagina to help prevent it 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 Dr. B C Shah to prescribe appropriate medication. 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 erectile dysfunction (the inability to get and maintain an erection) and loss of interest in sex are common side effects of pelvic radiotherapy.

Radiotherapy to other areas of your body 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 following radiotherapy, your doctor will discuss this with you before your treatment. 

Stiff joints and muscles

Radiotherapy can sometimes cause your muscles to tighten up and your joints to become stiff in the area being treated. You may also 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 will be able to recommend suitable exercises for you.

Long-term side effects of radiotherapy 

It is rare to develop severe, long-term side effects as a result of having radiotherapy. Your doctor will discuss the likelihood that you will experience side effects before you consent to treatment.

Sometimes, side effects can occur years after finishing a course of radiotherapy. Some of these may be permanent and can include:

  • Effects on fertility
  • Cosmetic changes to the skin
  • Tiny cracks in your pelvic bones (pelvic insufficiency fractures)
  • An inability to control your bowel (bowel incontinence)
  • Swelling in your arms or legs (lymphoedema)

These are discussed in more detail below.

Infertility and early menopause

In women, radiotherapy to the pelvic area exposes the ovaries to radiation. In pre-menopausal women, this may cause early menopause (where a woman's monthly periods stop) and infertility (the inability to get pregnant). This is often very upsetting, particularly for younger women who want to have a family.

Before having treatment, your doctor 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.

Cosmetic changes to the skin

Long-term changes to the skin can occur after having radiotherapy. Some people notice that their skin is thicker, a slightly darker colour and, occasionally, dimpled (like the peel of an orange). These changes usually improve over time.

Pelvic insufficiency fractures

Radiotherapy to your pelvic bones can cause tiny cracks, known as pelvic insufficiency fractures, to appear in the bones of your pelvis some time after treatment has finished. Pelvic insufficiency fractures are more likely to occur in people who have osteoporosis, a condition that causes brittle bones. 

Pelvic insufficiency fractures can be very painful, particularly during exercise. Resting should help to reduce the pain. You should report any new bone pain that you experience to your oncologist or GP.

Bowel incontinence

Bowel incontinence, sometimes known as faecal incontinence, is a rare side effect of radiotherapy to the pelvis. It is the inability to control your bowel movements which can result in faeces (stools) leaking from your rectum (back passage).

Bowel incontinence can be treated with dietary changes, medicines or a number of different surgical procedures. 


Radiotherapy can damage your body’s network of channels and glands that make up the lymphatic system. One of the functions of the lymphatic system is to drain excess fluid from your tissues. If the lymphatic system is damaged, fluid can build up and cause swelling and pain.

This is known as lymphoedema and it often occurs in the arms or legs although it can also affect other areas, such as the chest. Lymphoedema is usually associated with women who have had radiotherapy for breast cancer.

It may be possible to prevent lymphoedema occurring using appropriate skincare techniques and exercise. 

Recovering from radiotherapy 

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

Follow-up appointments

After your course of radiotherapy has finished, you will have an appointment with your oncologist (a cancer doctor who specialises in radiotherapy) to check on your progress.

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

Dr. B C Shah will be sent a report about your treatment. You will also be able to contact a member of your treatment team if you have any questions after your course of radiotherapy has finished.

Effects of radiotherapy

Despite the side effects mentioned here, radiotherapy can be a highly effective treatment, either in curing or controlling a cancer, or relieving symptoms.

The positive effects of radiotherapy usually take some time to become apparent. The treatment's benefits will depend on the type of cancer that you have and how advanced it is when treatment begins.

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