IoN
The UK trial confirming that low-risk thyroid cancer patients can safely avoid radioactive iodine, published in 2025.
Overview
IoN, trial NCT01398085 sponsored by Cancer Research UK and UCL and published in the Lancet in 2025, is the UK trial confirming that low-risk differentiated thyroid cancer patients can safely avoid radioactive iodine after thyroidectomy. It randomised 504 patients with pT1 to T2, node-negative tumours without adverse features to no radioiodine or radioiodine ablation and met its non-inferiority endpoint on recurrence-free status at five years, extending the ESTIMABL2 finding to pT2 tumours. Nuclide links it to thyroid cancer, radioiodine therapy, radioactive iodine, the low-risk thyroid cancer term and Cancer Research UK, and it replicates ESTIMABL2. Guideline bodies now recommend against routine ablation in this group, and whether patients and clinicians accept doing less is the practical question that remains.
- 98 vs 96 out of 100 alive without the cancer coming back at 5 years with No radioiodine compared with Radioiodine; 2 more per 100.
- Roughly one extra person helped for every 50 treated. That is a rough figure taken from the two percentages, not a guarantee for any one person.
- This is a surrogate endpoint: it measures the cancer being controlled or absent on scans and tests, which often, but not always, translates into living longer.
- These results apply to the people the trial enrolled: Low-risk differentiated thyroid cancer (pT1-T2, N0/Nx, no adverse features) after thyroidectomy: no radioiodine vs radioiodine ablation. People in a different situation may not see the same effect.
Numbers are from the trial as recorded here; see the source links in the table below. This is orientation, not medical advice: ask your team how closely the trial population matches you.
Similar pages
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