TriangleFOR PATIENTS · SOURCE READING
Radiation therapy, including radioactive iodine therapy
Source: Thyroid Cancer Treatment (PDQ®)–Patient Version, National Cancer Institute.
Source updated: February 12, 2025 · Captured 2026-09-09.
Selected source text with whitespace normalised. This Triangle page is not an NCI PDQ summary. Independent clinical review is pending.
Context: Treatment Option Overview / The following types of treatment are used:
Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy:
Source links and citations
External radiation therapy uses a machine outside the body to send radiation toward the area of the body with cancer. Sometimes the radiation is aimed directly at the tumor during surgery. This is called intraoperative radiation therapy.
Source links and citations
Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer.
Source links and citations
Radiation therapy may be given after surgery to kill any thyroid cancer cells that were not removed. Follicular and papillary thyroid cancers are sometimes treated with radioactive iodine (RAI) therapy. RAI is taken by mouth and collects in any remaining thyroid tissue, including thyroid cancer cells that have spread to other places in the body. Since only thyroid tissue takes up iodine, the RAI destroys thyroid tissue and thyroid cancer cells without harming other tissue. Before a full treatment dose of RAI is given, a small test-dose is given to see if the tumor takes up the iodine.
Source links and citations
The way the radiation therapy is given depends on the type and stage of the cancer being treated. External radiation therapy and radioactive iodine (RAI) therapy are used to treat thyroid cancer.
Source links and citations
Preserved source evidence · Independent clinical review pending · Not medical advice