What is radiotherapy?

Radiotherapy uses high-energy rays to treat disease. It can be given both externally and internally.

  • External radiotherapy aims high-energy x-rays at the affected area using a large machine.
  • Internal radiotherapy involves having radioactive material placed inside the body.

Radiotherapy works by destroying cancer cells in the area that’s being treated. Normal cells can also be damaged by radiotherapy, which may cause side effects. Cancer cells cannot repair themselves after radiotherapy, but normal cells usually can.

You can be given radiotherapy for different reasons. Doctors can give radiotherapy to try and destroy a tumour and cure the cancer. This is called curative treatment. It may be used with other treatments, such as surgery or chemotherapy.

If it’s not possible to cure the cancer, doctors may give you radiotherapy to help relieve symptoms you have. This is called palliative treatment.

Radiotherapy is sometimes given with chemotherapy. This is called chemoradiation.

The type of radiotherapy you’re given will depend on the type of cancer you have and your individual situation.

What is radiotherapy?

Radiotherapy uses high-energy rays, usually x-rays and similar rays (such as electrons), to treat disease. It destroys cancer cells in the area that’s treated.

Normal cells can also be damaged by radiotherapy. They can usually repair themselves, but cancer cells can’t.

Radiotherapy is carefully planned so that it avoids as much healthy tissue as possible. However, there will always be some healthy tissue that’s affected by the treatment and this will cause side effects.

Radiotherapy explained

Consultant Clinical Oncologist Vincent Khoo describes external beam radiotherapy, how it works, and what it involves.

Information about our videos

Radiotherapy explained

Consultant Clinical Oncologist Vincent Khoo describes external beam radiotherapy, how it works, and what it involves.

Information about our videos


Why radiotherapy is given

Many people with cancer will have radiotherapy as part of their cancer treatment. Radiotherapy may be given for different reasons.

Curative treatment

This is given with the aim of destroying a tumour and curing the cancer. It is also known as radical treatment.

Palliative treatment

This is given when it’s not possible to cure a cancer. You may have palliative treatment to control the growth of a tumour or relieve symptoms such as pain or coughing.


Ways of giving radiotherapy

There are two ways of giving radiotherapy:

Which way you have radiotherapy will depend on the type of cancer you have and where it is in the body. Some cancers are treated with both external and internal radiotherapy.

Chemoradiation

Sometimes chemotherapy is given at the same time as radiotherapy. This is called chemoradiation or chemoradiotherapy. Chemotherapy uses anti-cancer (cytotoxic) drugs to destroy cancer cells. The chemotherapy drugs can make the cancer cells more sensitive to radiotherapy.

Giving chemotherapy and radiotherapy together can make the side effects of treatment worse. Your doctor, radiographer or specialist nurse can give you more information about chemoradiotherapy and the possible side effects of this treatment.

Radiotherapy treatments are planned on an individual basis. This means that even if someone you know or have met has the same type of cancer as you, their radiotherapy treatment may be different.


Radiotherapy for children

Radiotherapy can be a frightening experience for both children and their parents. Understanding what’s involved can help.

Radiotherapy staff are used to treating children and can offer help and support. A play therapist will often be available as well to provide support.

We have more information about radiotherapy for children.

Back to Radiotherapy explained

Possible side effects

There are things you can do to help manage the possible side effects of radiotherapy treatment.

Making a radiotherapy mask

During radiotherapy to the head and neck a mask is used to help you keep still so that exactly the right area is treated.

Who might I meet?

You will meet many different specialists before, during and after radiotherapy treatment.

After treatment

It can take time to recover from radiotherapy. Support is there if you have any problems.