Internal radiation therapy

Internal radiation therapy places radioactive materials in the body. A larger dose of radiation can be given with internal radiation therapy than with external radiation therapy. Radiation can be given directly to cancer cells and so less radiation goes to nearby normal tissue. But internal radiation therapy can only be used to treat certain types of cancer.

Types of internal radiation therapy

There are different ways of giving internal radiation therapy.


Brachytherapy places a sealed container of a radioactive substance directly into a tumour (called an implant). It can also be placed in the area where a tumour was removed. Radioactive implants come in different forms, including special applicators, thin wires, tubes (catheters), ribbons, needles, capsules and small seeds. Depending on the type of implant, the radiation source will stay in place for minutes, hours or days, or it will be permanent. Permanent implants are usually very small, often about the size of a grain of rice.

Types of implants

Interstitial brachytherapy places the implant right into a tumour. It may be used to treat prostate or head and neck tumours. It may be given along with external radiation therapy.

Intracavitary brachytherapy places the implant in a special applicator inside a body cavity. It is most commonly used for cancers of the female reproductive tract, such as cervical cancer.

Intraluminal brachytherapy places the implant in a special applicator inside a body passage. It may be used to treat esophageal or lung cancer. It can be given along with external radiation therapy to give an additional boost of radiation. It is also called transluminal brachytherapy.

Plaque brachytherapy places a very small implant on the surface of a tumour. It may be used to treat some types of eye or skin tumours. It is also called surface brachytherapy.

High-dose and low-dose brachytherapy

Brachytherapy may be given as high dose or low dose.

High-dose-rate (HDR) brachytherapy delivers a single high dose of radiation in a very short period of time. A single treatment usually takes a few minutes. The radioactive material travels from a special high-dose-rate machine attached to tubes or needles inserted into the tumour. Once it is finished, the material goes back into the machine so that no radioactive material is left in the body. The person can usually go home after the treatment. Sometimes, a few treatments may need to be given over a few days or weeks. If so, the applicator may be left in between treatments.

Low-dose-rate (LDR) brachytherapy delivers continuous low doses of radiation over hours or days. Doctors implant a container for the radioactive material in the tumour. The radioactive material is inserted into the implanted container. You may need to be in the hospital for the first few days after the implant is placed, while the radiation is most active. The implants become less radioactive each day. The radiation in the body is very weak by the time you go home, but some safety precautions may be needed.

Radioisotope therapy

Radioisotope therapy, sometimes called radiopharmaceutical therapy, radionuclide therapy or radioligand therapy (RLT), travels through the blood to reach cells all over the body (systemic radiation). This radioactive material is not sealed in a container like brachytherapy. Radioisotope therapy is used to treat certain types of cancer, such as thyroid cancer, or to relieve pain when cancer has spread to the bone. Radioisotope therapy is given by mouth (orally) in a capsule or drink, or by intravenous injections.

Radioimmunotherapy (RIT)

Radioimmunotherapy (RIT) combines radiation therapy with monoclonal antibodies, a type of immunotherapy. Monoclonal antibodies specifically target cancer cells. When a RIT is injected into the body, the monoclonal antibody delivers the radioactive substance to the tumour.


Radioembolization combines radiation therapy with embolization. It can also be called selective internal radiation therapy. It gives radiation directly to tumours using tiny radioactive beads (called microspheres). Using a catheter, these beads are placed inside the blood vessels that feed a tumour, delivering a high dose of radiation to the tumour and also blocking the supply of blood to the cancer cells.

Before treatment

Your first appointment will be with the radiation oncologist. They will go over your medical records, will do a physical exam and may order tests. They will discuss the specific type of internal radiation therapy being recommended for your individual case, treatment options and side effects. If you have any questions about radiation therapy and your treatment, ask the radiation oncologist.

Treatment plan

Your treatment plan includes the amount (dose) of radiation therapy you will receive and the type of radioactive substance or implant.

Total radiation dose is the total amount of radiation you will receive. It is precisely calculated and ordered in units called grays (Gy). Depending on your treatment plan, you may receive your total dose of radiation all in one treatment or it may be divided up into several treatments of smaller doses (called fractions). Sometimes external radiation therapy is used along with internal radiation therapy.

The total dose of radiation depends on:

  • the type of radioactive material
  • the type of cancer
  • how sensitive the tumour is to radiation therapy (radiosensitivity)
  • the tumour location
  • the amount of tissue to be treated
  • whether other cancer treatments have been or will also be given
  • your overall health

Half-life is the time it takes for half of a material’s radioactivity to disappear. Different radioactive materials have different half-lives. The half-life will also determine how long safety precautions need to be taken after treatment.

During treatment

Internal radiation therapy is given in a hospital or cancer treatment centre. It may be given to you as an outpatient, but sometimes you may have to stay in the hospital overnight. This depends on the part of the body being treated, the type of internal radiation therapy and your overall health.

Brachytherapy gives radiation therapy as implants directly to the tumour or area where the tumour was removed. Doctors may use an ultrasound, CT scan or other imaging tests to help make sure that they place the implants into the tissue or body cavity in the right spot. Brachytherapy implants are usually placed in an operating room. You will be given a general anesthetic (you will be unconscious) or a sedative to help you relax.

Other types of internal radiation therapy, such as radioisotope therapy and RIT, may be given as intravenous injections (directly into the vein) or orally (by mouth). The radioactive substance travels to cancer cells and is absorbed by them in certain parts of the body. One dose is usually all that is needed.

Depending on the type of internal radiation therapy you receive, you may need to stay in a private room and limit time with visitors while the radiation is most active. The length of time depends on the type and dose of radioactive material. For some large implants, you may need to lie still during treatment. Some activities may also be restricted, but you can usually still read, watch television, listen to music or talk on the telephone. A medical physicist may regularly measure the level of radioactivity in the room. They may also measure radioactivity in people receiving radiation therapy before they are discharged from the hospital.

After treatment

The radiation therapy team will follow your progress throughout your treatment sessions and adjust the dose or length of treatment as needed. They may do blood tests or imaging tests at different times during your treatment to see how your tumour is responding to radiation therapy.

Recovery during and after radiation therapy will depend on the type of cancer, the stage of cancer, the radiation dose and your overall health. Some people can work and continue to do their regular leisure activities while receiving radiation therapy. Others find they tire easily and need to rest more.

Temporary implants will be removed when treatment is over. Usually this is done in your hospital room and does not need anesthesia, but the area may be sore or tender for a few days. Once an implant is removed, your body does not give off radiation. Permanent implants give off small doses of radiation over a few weeks or months. The implant or radioactive isotope becomes less radioactive each day. The radiation doesn’t usually go much farther than the area of the implant so your body fluids (such as urine and stool) are usually not radioactive. Your radiation therapy team may ask you to take some safety precautions, such as not having contact with pregnant women and small children, especially right after you get the implants. Your radiation therapy team will provide instructions and information about any safety precautions you need to follow and for how long. Talk to your radiation therapy team if you have any safety concerns or questions.

People who receive radiation therapy that travels all through the body, such as radioisotope therapy and RIT, may need to take special precautions for the first few days after treatment. Your radiation therapy team will discuss these precautions with you. They may include:

  • Wash your hands well after using the washroom.
  • Use separate dishes, cutlery and towels.
  • Drink plenty of fluids to flush the radioactive material out of your body.
  • Do not have sex or sexual contact.
  • Do not have contact with infants, children and pregnant women.

Your radiation therapy team will give you any additional precautions that may be necessary in your particular case.

Expert review and references

  • American Cancer Society. A Guide to Radiation Therapy. 2015.
  • American Society of Clinical Oncology. What to Expect When Having Radiation Therapy. 2016.
  • Radiotherapy. Cancer Research UK. CancerHelp UK. Cancer Research UK; 2009.
  • National Cancer Institute. FactSheet: Radiation Therapy for Cancer. Bethseda, MD: National Cancer Institute; 2010.
  • National Cancer Institute. Intraocular (Uveal) Melanoma Treatment - for Health Professionals (PDQ®). National Cancer Institute; 2015:
  • National Cancer Institute. What To Know About Brachytherapy. 2012.
  • Princess Margaret Cancer Centre. What To Expect: Radiation Treatment. 2016.
  • Princess Margaret Cancer Centre. Your Radiation Therapy at the Princess Margaret Hospital. 2011.
  • Radiological Society of North America. Prostate Cancer Treatment. 2017.
  • Radiological Society of North America. Brachytherapy. 2016.
  • Radiological Society of North America. Radioembolization (Y90). 2015.
  • Radiological Society of North America. Radioimmunotherapy (RIT). 2015.

Medical disclaimer

The information that the Canadian Cancer Society provides does not replace your relationship with your doctor. The information is for your general use, so be sure to talk to a qualified healthcare professional before making medical decisions or if you have questions about your health.

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