Health Topic

Radiation Therapy

Radiation therapy is treatment used to stop the spread of cancer. It must be carefully done to minimize side effects and maximize benefits.

Reviewed Reviewed by a registered pharmacistGeneral information

Also called: Brachytherapy · Radiotherapy

Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.

About Radiation Therapy

Radiation therapy is a cancer treatment. It uses high doses of radiation to kill cancer cells and stop them from spreading. It may also be used for easing cancer symptoms. Radiation therapy may damage healthy cells. They can usually repair themselves more easily than cancer cells.

You may need days or weeks of treatment before the radiation starts killing cancer cells. But cancer cells should keep dying for weeks or months after your treatment ends.

Radiation therapy treats many types of cancer. It may be used at different times or for different reasons during your treatment. Sometimes radiation is used with other treatments, like surgery, chemotherapy, or immunotherapy.

You may get radiation therapy once a day or in smaller doses twice a day for a few weeks. The radiation may be external, from special machines, or internal from radioactive substances placed inside your body.

The type of radiation therapy you get depends on many factors, including:

  • The type of cancer
  • The size of the cancer
  • Where the cancer is in your body
  • How close the cancer is to normal tissues that are sensitive to radiation
  • How far the radiation needs to travel into your body
  • Your general health and medical history
  • Whether you will have other types of cancer treatment
  • Other factors, such as your age and other medical conditions

Your treatment must be carefully planned to reduce side effects. Radiation therapy can damage normal cells as well as cancer cells. Healthy cells usually repair themselves but damaging them can cause side effects.

Side effects can vary from person to person. Common side effects include skin changes and fatigue. Other side effects depend on the part of your body being treated. Most side effects go away a few months after you are done with treatment.

It sits within Cancers and Surgery and Rehabilitation.

The lead U.S. institute for this subject is the National Cancer Institute.

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Research on Radiation Therapy

8,808 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.

What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.

Research currently under way

Research already completed

Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.

Where to read more

Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.

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Related Issues

Clinical Trials

Medical subject headings

Clinicians and researchers index this subject under Radiotherapy. These are the terms to use when searching medical literature.

This page is built from the MedlinePlus health topic record for Radiation Therapy, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.