About Radiotherapy

What is radiotherapy?

Radiotherapy involves using radiation, such as x-rays, to treat cancer. It may be used to shrink tumours and cure cancer, reduce the risk of cancer returning or to help relieve symptoms. Radiotherapy can be carried out externally, from outside of the body, or internally, from within the body. Patients within the ARCHERY trial are likely to be receiving external radiotherapy.

How does radiotherapy work?

In external radiotherapy a machine directs radiation beams from outside the body at the cancer. These radiation beams damage the DNA of the cancer cells. DNA is the genetic code controlling how cells behave. If the DNA is damaged beyond repair, then the cancer cells cannot grow. This will either slow the growth of the cancer or lead to damaged cells dying. Once damaged cells die, they can be destroyed and removed by the body. 

Brachytherapy is a type of internal radiotherapy. A small radioactive material called a source is put into your body, inside or close to the cancer.

There are different types of radioactive sources (also called implants) such as seeds, wires or discs. They deliver radiotherapy to the affected area, destroying the cancer cells. Healthy tissue near to the cancer is exposed to a lot less radiation, reducing the damage to healthy cells.

How is radiotherapy treatment carried out?


Depending on the type of cancer, different types of radiation beam are used. These beams are made up of very small particles. During treatment, you cannot see or feel the radiation beams.  The type of machine used may also vary depending on the type and location of the cancer. The radiotherapy experience is very similar for all.

Radiation is usually applied to both cancer cells and a border of healthy cells around the cancer. This is to make sure the cancer does not spread or come back. Because radiation has the same effect on healthy cells and cancer cells, the smallest possible amount will be used on healthy cells. 


Your doctor works out how much radiation you need. This affects how long the radioactive source stays inside you. This can be anything from several minutes to a few days, or it can stay in place permanently. If the source stays inside you permanently, it stops giving off radiation after a few weeks or months.

What does radiotherapy feel like?

The machine does not touch the body and the beams cannot be felt. The radiotherapy session itself will not hurt. The most common type of machine used is called a linear accelerator (LINAC). This uses electricity to create the beams of radiation. Because of this the machine makes a buzzing sound when on. The machines are quite big, as are the rooms they are used in. 

The treatment itself is not painful. You may hear a slight buzzing noise from the radiotherapy machine while you are having the treatment. In some treatment rooms you can listen to music. This may help you relax.

Most curative (radical) radiotherapy involves having treatment from several different directions. To do this, the radiotherapy machine may move around you into different positions during your radiotherapy. This may happen several times. You will need to lie still. Sometimes, the radiographers will come into the treatment room to change the position of the machine.

During your treatment, the radiotherapy machine may take pictures (x-rays or CT scans) of the area being treated. These pictures may be taken on the first day and again on other days. They are used to help make sure the treatment is given accurately and to show how well treatment is working, as treatment takes time to work.

What are the side effects of radiotherapy?

Side effects depend on where in your body the radiotherapy is being applied. Other treatments may also be used with radiotherapy that cause their own side effects. If side effects occur, these will be felt a few hours after treatment.

Short term side effects include red or sore skin, swelling and hair loss in the area of treatment. Tiredness, feeling sick and headaches are also common temporary side-effects. Long term effects will depend on the location and type of cancer and how much healthy tissue needs to be treated. 

Some people are able to carry on working around their radiotherapy treatment, whilst others may need to stay home or be in hospital. 

External radiotherapy does not make you radioactive. It is safe to be around other people after treatment, including children. In the case of internal radiotherapy, additional safety precautions may be required whilst the radioactive source is in place. 

How is radiotherapy planned?

The method, strength, positioning and length of radiotherapy treatment is devised by a team of doctors and other specialists. These treatment plans are specific to each patient and their cancer type. The AI software used in the ARCHERY study aims to make the process of planning this faster and more efficient. You can learn more about the AI software on the 'what is the radiation planning assistant (RPA)' page.

Archery is funded by Rising Tide and NIH