External beam radiation therapy for thyroid cancer

External beam radiation therapy (also known as radiotherapy) is the use of high-energy x-rays or electron beams to kill or damage cancer cells. Radiation is delivered precisely to the affected area, which reduces treatment time and side effects.

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When is external beam radiation therapy used?

Most people diagnosed with thyroid cancer do not need external beam radiation therapy. In a small number of cases, it may be given in the following circumstances:

  • after surgery and radioactive iodine treatment if the cancer has not been completely removed or if there is a high risk of the cancer coming back (recurrence)
  • as palliative treatment to relieve symptoms if the cancer has spread to nearby tissue or structures
  • to help control medullary or anaplastic thyroid cancer because these types do not respond to RAI.

Planning session

Before the treatment starts, you will have a planning session. The radiation therapist will take CT scans to determine the exact area to be treated, and may make small marks or tattoos on your skin. This ensures the same part of your body is targeted during each treatment session.

You may be fitted for a plastic mask to wear during treatment. This will help you stay still so that the radiation is targeted at the same area of your neck during each session. You can see and breathe through the mask, but it may feel strange and uncomfortable at first. The radiation therapy team can help you manage this.

Having treatment

Radiation therapy is usually given five days a week over several weeks. Treatment sessions usually take about 10 minutes, but it will take longer to position the machine correctly.

Side effects of external beam radiation therapy

Many people will develop temporary side effects during treatment. Common side effects include feeling tired, difficulty swallowing, sore throat, dry mouth, and red, dry, itchy, sore or ulcerated skin. Most of these will disappear within a few weeks or months. Your treatment team can help you prevent or manage any side effects.

Video: What is radiation therapy?

Watch this short video to learn more about radiation therapy.

This information was last reviewed in January 2018
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