How radiotherapy works

This section aims to answer some common questions about radiotherapy and how it works as a treatment for cancer.

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 tumour using a machine called a linear accelerator.
  • Internal radiotherapy involves having radioactive material placed inside the body.

How does it work?

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

Aim of radiotherapy

You can be given radiotherapy for different reasons. You may be given radiotherapy to try and destroy a tumour and cure the cancer. This is called curative or radical treatment. It may be used in combination 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.

The type of radiotherapy you’re given will depend on your individual situation.

Last updated: March 2023