Radiotherapy can be used for the following reasons:
  • For some cancers that are diagnosed early (eg cancers of the skin, cervix, prostate, lungs, thyroid and brain), it may be the only treatment needed to cure the cancer. This is known as primary therapy or radical radiotherapy.
  • To reduce the size of some cancers before surgery. This is called neo-adjuvant treatment.
  • To make sure all the cancer cells are destroyed after surgery, and to treat local spread of the cancer (such as in the treatment of breast cancer). This is called adjuvant treatment.
  • In the emergency treatment of a cancer pressing on the spinal cord, to reduce the size of the cancer and prevent damage to the nerves.
  • In advanced cancer to slow down the progress of the disease and relieve pain and other symptoms

A course of radiotherapy usually requires daily visits on weekdays for several weeks.

Preparing for radiotherapy

Planning a course of radiotherapy can take some time. To find the exact position of the cancer, your doctor will use X-ray pictures and CT (computerised tomography) scans, which give a three-dimensional picture of your internal organs. You may also have MRI scans, which uses magnets and radiowaves to produce images of the inside of your body. Before your treatment starts you will need to come to the radiotherapy department where a special machine called a simulator is used to help plan the exact location and dose of radiation.

The area to be treated has to be positioned accurately each time. To help this you may have a few tiny dots tattooed on your skin. If the area has to be kept very still, you may need to have a mould made. For example, if your head and neck area is to be treated, you may need to wear a see-through plastic mask or brace to make sure you head remains in exactly the same position for each treatment.

You will have a blood test to see if you have anaemia (low red cell number in your blood). If so, you may need to have a blood transfusion to increase the amount of oxygen your blood can carry around your body. This helps make some cancers more sensitive to radiotherapy.

What happens during radiotherapy?

In most hospitals, a number of different professionals are involved in providing treatment. This is known as a multidisciplinary team. A clinical oncologist (a doctor who specialises in cancer care using radiotherapy) will oversee the treatment. The radiotherapy equipment is operated by a therapy radiographer, a healthcare professional trained in using X-rays for treatment. A radiologist will help with diagnosis and assessing the response to treatment. A nurse specialist is often your key contact during treatment and will be available to offer help and support.

You may see other health professionals including a physiotherapist, dietician and pharmacist. Behind the scenes, medical physicists are responsible for calculating safe and effective doses of radiation.

There are two main types of radiotherapy treatment: external beam radiotherapy and internal radiotherapy.

External beam radiotherapy

External beam radiotherapy is delivered by a machine known as a linear accelerator. It produces a high-powered beam of radiation, which is often X-rays. The dose of X-rays is at least 40 times greater than for taking an X-ray picture.

The course of treatment will be planned by a clinical oncologist. He or she will a plan your treatment by taking into account the size of the cancer, its likely sensitivity to radiation and the sensitivity of the surrounding tissues. He or she will also take into account your general health and fitness, and will discuss possible short and long-term side effects that you may need to prepare for.

The number and duration of the radiotherapy sessions depends on the type of cancer and where it's located in your body. A superficial skin cancer may need only a few treatments, whereas a cancer deeper in the body may need longer treatment. It may also depend on whether you are having treatment to cure the cancer or treatment to reduce symptoms.

The total amount of radiation you will need is measured in Grays (abbreviated to Gy). The overall dose is given in daily doses called 'fractions'. For each fraction of radiotherapy you will be asked to sit or lie down in a fixed position.

The radiotherapy equipment can be positioned with great accuracy to target the beam of radiation exactly on the right spot. This may involve lying down while the machine rotates around you, or you may be asked to sit in a chair while the beam is directed at a tumour that is near the surface of your skin. The machine won't actually touch you at any point, but it can be quite noisy, with whirring and buzzing sounds. There is an intercom so you can communicate with the radiographer at all times.

Radiotherapy won't make you become radioactive during or after the treatment because no radiation-producing material gets inside the body. You will be able to carry on with many of your normal daily activities. However, you may feel tired during and after your treatment so it's a good idea to ask friends and family for help if you need it.

Internal radiotherapy

Internal radiotherapy is where the source of radioactivity is put inside your body so it can get closer to the cancer. This can be done in two ways:


This is when a solid source of radioactivity is put next to a tumour to give a high dose of radiotherapy. This means the effect on body tissue around the cancer is as little as possible. Brachytherapy can be used to treat cancers of the cervix, womb (uterus), prostate and skin.

For women who have gynaecological cancers, such as cervical cancer, the radiation source is placed inside the vagina during the treatment. This means you need to stay in hospital for a day or two during treatment. For other cancers, you may need to have a minor operation to put the radioactive source into your body. This will be removed after about a week. Hospital visiting will be restricted at this time because you will be radioactive while the source is in place.

For prostate cancer, small radioactive pellets, known as seeds, are placed into the prostate gland and deliver a steady low dose of radiation. This type of source gradually loses it's radioactivity and stays in your body permanently.

Radioisotope therapy

This is when a radioactive substance, a radioisotope, is administered. It may be given either as an injection into a vein, capsules you can swallow, or as a liquid you can drink. Radioisotope treatment is often used for cancers of the thyroid gland.


After radioisotope therapy your body will give off small amounts of radiation so you may need to stay in isolation for some time after treatment and then take precautions, such as not getting close to pregnant women or children, for about 10 days. The radioactive material is flushed out by the kidneys so your urine may be radioactive and you will be given advice on precautions - such as flushing the toilet twice after urinating - to minimise risks to other people.

Recovering from radiotherapy

After your treatment, your clinical oncologist will arrange a follow-up appointment to check how you're recovering from any side-effects and what your response has been to the radiotherapy. This is a good opportunity to ask about any long-term side-effects that you might expect to have after your treatment.

Patient support groups can give you support and advice on recovering after radiotherapy.

What are the risks?


These are the unwanted, but mostly temporary effects of a successful treatment. The side-effects are very dependent on what part of the body has been treated. You will be given information about the side-effects specific to you before you start treatment.

Depending on which part of your body is being treated, possible side-effects immediately after radiotherapy include:

  • tiredness
  • loss of appetite
  • feeling sick and vomiting
  • diarrhoea
  • skin may become red, itchy and sometimes sore, like sunburn
  • coughing and shortness of breath
  • dry mouth or sore throat, causing difficulty swallowing
  • losing weight
  • hair loss - usually temporary but it can be permanent - only happens in the area of the body being treated
  • emotional symptoms - feeling low, depressed or anxious after treatment
  • stiffness of joints and muscles

Radiotherapy can also cause some long-term side-effects such as:

  • tiredness
  • scarring of the skin in the area that has been treated (this is called fibrosis)
  • other tissues can also become scarred and less stretchy (eg your bladder may hold less urine)
  • darkening of the skin
  • hair may grow back a different texture and colour
  • hair loss is sometimes permanent
  • tiny red marks on the skin from broken blood vessels
  • swelling of the arms and legs, due to the blockage of lymph vessels (this is called lymphoedema)
  • shortness of breath - if you have had radiotherapy to your chest
  • difficulty swallowing due to narrowing of the gullet (oesophagus)

Some, but not all, people who have radiotherapy to the pelvic region may have side effects related to their bowel, bladder or sexual function. Your oncologist and specialist nurse will be able to offer advice and support.

Very rarely radiotherapy can cause a second cancer to develop several years after treatment. The benefits of the radiotherapy outweigh this risk but it may be something that your oncologist will mention to you and is also one of the reasons patients are followed up.

Last Updated: Aug 2017
Please note that all medical health articles featured on our website have been reviewed by Quality Healthcare doctors. The articles are for general information only and are not medical opinions nor should the contents be used to replace the need for personal consultation with a qualified health professional on the reader’s medical condition.