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External Radiation Therapy for Thyroid Cancer
External radiation therapy uses high-energy rays (or particles) to destroy cancer cells or slow their growth. A carefully focused beam of radiation is delivered from a machine outside the body.
When might external radiation be used for thyroid cancer?
This type of radiation therapy is most often used to treat medullary thyroid cancer or anaplastic thyroid cancer. These cancers don’t take up iodine.
For cancers that do take up iodine (most papillary and follicular thyroid cancers), radioiodine therapy is usually a better treatment option. However, if a papillary or follicular cancer isn’t helped by radioiodine therapy, external radiation therapy may be an option for treatment.
External radiation therapy is most often used for cancers that have spread outside of the thyroid. This might be done to help treat the cancer (or to treat symptoms such as pain), or to help lower the chance of cancer coming back in the neck after surgery.
How is external radiation given?
External radiation therapy to the neck area is usually given 5 days a week for several weeks.
Before your treatments start, the medical team will take careful measurements to find the proper dose of radiation and the correct angles for aiming the radiation beams.
The treatment itself is painless and much like getting a regular x-ray. Each treatment lasts only a few minutes, although the setup time (getting you into place for treatment) usually takes longer.
Possible side effects of radiation therapy for thyroid cancer
The main drawback of this treatment is that the radiation can damage nearby healthy tissue along with the cancer cells. Possible side effects include:
- Skin changes (similar to a sunburn) in the area being treated
- Trouble swallowing
- Dry mouth
- Hoarseness
- Feeling very tired
To reduce the risk of side effects, doctors carefully figure out the exact dose needed and aim the beam as accurately as they can to hit the target. This is often done with an advanced type of treatment known as intensity-modulated radiation therapy (IMRT).
More information about radiation therapy
To learn more about how radiation is used to treat cancer, see Radiation Therapy.
To learn about some of the side effects listed here and how to manage them, see Managing Cancer-related Side Effects.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.
Asban A, Patel AJ, Reddy S, Wang T, Balentine CJ, Chen H. Chapter 68: Cancer of the Endocrine System. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 6th ed. Philadelphia, Pa. Elsevier: 2020.
American Thyroid Association Guidelines Task Force, Kloos RT, Eng C, Evans DB, et al. Medullary thyroid cancer: Management guidelines of the American Thyroid Association. Thyroid. 2015 25;19:567-610.
American Thyroid Association (ATA) Guidelines Taskforce on Thyroid Nodules and Differentiated Thyroid Cancer. Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid. 2016; 26:1-133.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Thyroid Carcinoma. V.2.2024. Accessed at https://www.nccn.org/professionals/physician_gls/pdf/thyroid.pdf on April 15, 2024.
Tuttle RM. Medullary thyroid cancer: Surgical treatment and prognosis. UpToDate. 2024. Accessed at https://www.uptodate.com/contents/medullary-thyroid-cancer-surgical-treatment-and-prognosis on April 17, 2024.
Tuttle RM, Lee NY. Differentiated thyroid cancer: External beam radiotherapy. UpToDate. 2024. Accessed at https://www.uptodate.com/contents/differentiated-thyroid-cancer-external-beam-radiotherapy on April 17, 2024.
Tuttle RM, Sherman EJ. Anaplastic thyroid cancer. UpToDate. 2024. Accessed at https://www.uptodate.com/contents/anaplastic-thyroid-cancer on April 17, 2024.
Last Revised: August 23, 2024
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