# ESTIMABL2

Source: https://onco.cc/trials/estimabl2/  
OnCo record `estimabl2` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Proved that most people with small, low-risk thyroid cancers can skip radioactive iodine after surgery without any increase in recurrence.

## Summary

ESTIMABL2, trial NCT01837745 sponsored by Gustave Roussy and the French Endocrine Tumour Group and reported in 2022, proved that most people with small, low-risk differentiated thyroid cancers can skip radioactive iodine after total thyroidectomy without any increase in recurrence. It randomised 776 patients with pT1a to T1b, node-negative tumours to no radioiodine or 1.1 GBq ablation and met its non-inferiority endpoint on event-free status at three years, confirmed at five years in 2024. OnCo links it to thyroid cancer, radioiodine therapy, radioactive iodine, the low-risk thyroid cancer term, Gustave Roussy and Martin Schlumberger, and together with IoN and HiLo it removed radioiodine from routine low-risk care in ATA and ESMO guidance; the UK IoN trial reached the same conclusion. Whether the same holds for larger low-risk tumours, as IoN suggested for pT2, is the remaining question.

## Fields

- Kind: Trial
- Status: positive
- Last checked: 2026-09-07
- Registry id: NCT01837745
- Phase: 3
- Setting: Low-risk differentiated thyroid cancer (pT1a-T1b N0/Nx) after total thyroidectomy: no radioiodine vs 1.1 GBq ablation
- Sponsor: Gustave Roussy / French Endocrine Tumour Group
- Enrolled: 776
- Result: 3-year event-free 95.6% vs 95.9% (non-inferior).
- Outcomes: Patients without events at 3 years: No radioiodine 95.6% vs Radioiodine 1.1 GBq 95.9%
- Replication: IoN (UK, Lancet 2025) reached the same conclusion in a pooled analysis.

## Sources

- ClinicalTrials.gov NCT01837745: https://clinicaltrials.gov/study/NCT01837745
- NEJM 2022: https://www.nejm.org/doi/full/10.1056/NEJMoa2111953
- 5-year follow-up: https://www.thelancet.com/journals/landia/article/PIIS2213-8587(24)00276-6/fulltext

## Connected records

- cancers: [Thyroid cancer](https://onco.cc/cancers/thyroid/)
- technologies: [Radioiodine therapy and whole-body iodine scanning](https://onco.cc/technologies/radioiodine-therapy/)
- institutions: [Gustave Roussy](https://onco.cc/institutions/gustave-roussy/)
- terms: [Low-risk differentiated thyroid cancer (ATA risk)](https://onco.cc/terms/low-risk-dtc/)
- people: [Martin Schlumberger](https://onco.cc/people/martin-schlumberger/)
- drugs: [Radioactive iodine (I-131)](https://onco.cc/drugs/radioactive-iodine/)
- key papers: [ESTIMABL2: thyroidectomy without radioiodine in patients with low-risk thyroid cancer](https://onco.cc/key-papers/paper-estimabl2-leboulleux-nejm-2022/)
- roadmaps: [Radiotherapy roadmap: X-rays → shaped beams → fewer fractions, particles and FLASH](https://onco.cc/roadmaps/radiation-roadmap/), [Surgery roadmap: radical operations → less surgery → no surgery when a drug has done the work](https://onco.cc/roadmaps/surgery-roadmap/)

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