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What internal radiotherapy is

Nurse and patients talking about cancer

This page tells you about internal radiotherapy, which uses radioactive metals or liquids (isotopes) to treat cancer. There is information about the two main types of internal radiotherapy. Read about


What internal radiotherapy is

Internal radiotherapy can mean treating cancer by using radioactive liquids that you drink or have injected into a vein. Or a type called brachytherapy uses radioactive metals or liquids put inside the body close to the area of the cancer. 

Different types of internal radiotherapy are used to treat different cancers. 


Radioactive liquids

Radioactive liquids to treat cancer are given either as a drink or by injection. Examples include

  • Radioactive phosphorus – used for blood disorders
  • Radioactive radium – used for cancer that has spread to the bones (secondary bone cancer)
  • Radioactive strontium – used for secondary bone cancers
  • Radioactive iodine – used for benign (non cancerous) thyroid conditions and thyroid cancer

The radioactive part of the liquid is called an isotope. It may be attached to another substance, which is designed to take the isotope into the tumour.


Radioactive implants

Internal radiotherapy implants are radioactive metal wires, seeds, or tubes put into your body, inside or close to a tumour. The radioactive metal is called a source and is left inside the body for a period of time. In many types of cancer the source is taken out after a few minutes or a few days. While it is in place you need to avoid close contact with people and may need to be looked after in a single room in hospital.

In some types of cancer, small metal implants, or seeds, are left in the body permanently. These implants are made of radioactive gold or contain radioactive iodine. They give a very high dose of radiation to the area of the cancer cells. For most types of implants the radioactivity only travels a few millimetres through body tissue and so it can't be detected outside the body. For some people the radioactivity can be detected outside the body at first. They need to avoid close contact with people until the radioactivity drops to a safe level.


More information about internal radiotherapy

Find out about

Types of internal radiotherapy

Side effects of radiotherapy

Cancer and treatments reading list

For general information and support

Contact the Cancer Research UK nurses on freephone 0808 800 4040 (Open 9am to 5pm, Monday to Friday)

Share experiences on our online forum – Cancer Chat.

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Updated: 26 April 2016