# Radioiodine therapy and whole-body iodine scanning

Source: https://onco.cc/technologies/radioiodine-therapy/  
OnCo record `radioiodine-therapy` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Using the thyroid's natural appetite for iodine to image and treat thyroid cancer with a radioactive form of it. The oldest theranostic, and now used more selectively than it was.

## Summary

I-123 or low-activity I-131 scans map iodine-avid tissue; therapeutic I-131 ablates remnants or treats metastases. Randomised trials (HiLo, ESTIMABL1/2, IoN) have progressively reduced activity and then removed ablation for low-risk disease. Refractory disease (no uptake, or progression despite uptake) defines the population for kinase inhibitors; redifferentiation with MEK/BRAF inhibitors can restore uptake in selected patients.

## Fields

- Kind: Technology
- Status: standard-of-care
- Last checked: 2026-09-07
- Principle: Thyroid cells take up iodine through the sodium-iodide symporter after TSH stimulation; the beta emission treats, the gamma emission images.
- Since: 1946
- Strengths: Highly selective without any engineered targeting; Cheap, oral, curative in iodine-avid metastatic disease
- Limitations: Dedifferentiated tumours lose uptake; Salivary toxicity; radiation precautions; second cancers at high cumulative activity

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Isotopes_of_iodine#Iodine-131
- Wikipedia: https://en.wikipedia.org/wiki/Isotopes_of_iodine#Iodine-131

## Connected records

- cancers: [Follicular thyroid cancer](https://onco.cc/cancers/follicular-thyroid-cancer/), [Papillary thyroid cancer](https://onco.cc/cancers/papillary-thyroid-cancer/), [Thyroid cancer](https://onco.cc/cancers/thyroid/)
- fronts: [Radiation Therapy](https://onco.cc/fronts/radiation/), [Radiopharmaceuticals & Theranostics](https://onco.cc/fronts/radiopharma/)
- technologies: [Radioligand therapy (beta emitters)](https://onco.cc/technologies/radioligand-therapy/), [SPECT & bone scan](https://onco.cc/technologies/spect/)
- drugs: [Radioactive iodine (I-131)](https://onco.cc/drugs/radioactive-iodine/), [Thyrotropin alfa](https://onco.cc/drugs/thyrotropin-alfa/)
- terms: [Low-risk differentiated thyroid cancer (ATA risk)](https://onco.cc/terms/low-risk-dtc/), [PRRT (peptide receptor radionuclide therapy)](https://onco.cc/terms/prrt-term/), [Radioiodine therapy (I-131)](https://onco.cc/terms/radioiodine-term/), [Radioiodine-refractory (RAI-R) thyroid cancer](https://onco.cc/terms/rai-refractory/), [Theranostics](https://onco.cc/terms/theranostics/), [Thyroidectomy](https://onco.cc/terms/thyroidectomy/)
- trials: [ASTRA](https://onco.cc/trials/astra/), [ESTIMABL2](https://onco.cc/trials/estimabl2/), [HiLo](https://onco.cc/trials/hilo/), [IoN](https://onco.cc/trials/ion-trial/)
- pairings: [MAPK inhibitor redifferentiation → radioiodine](https://onco.cc/pairings/redifferentiation-rai/)

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