# HiLo

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

## TL;DR

Showed a third of the usual radioactive iodine dose ablates the thyroid remnant just as well, with fewer side effects and less time in isolation.

## Summary

HiLo, trial NCT00415233 sponsored by Cancer Research UK and reported in 2012, showed that a third of the usual radioactive iodine dose ablates the thyroid remnant just as well as the high dose in differentiated thyroid cancer, with fewer side effects and less time in isolation. It randomised 438 patients needing ablation to 1.1 GBq or 3.7 GBq of radioiodine, with recombinant TSH or thyroid hormone withdrawal, and met its non-inferiority endpoint on successful ablation, while recombinant TSH avoided hypothyroid symptoms. OnCo links it to thyroid cancer, radioiodine therapy, radioactive iodine and Cancer Research UK, and the French ESTIMABL1 trial replicated low-dose non-inferiority at the same time. Low-dose ablation became standard for intermediate-risk disease and the trial paved the way to omitting ablation altogether in low-risk disease, as ESTIMABL2 and IoN then showed.

## Fields

- Kind: Trial
- Status: positive
- Last checked: 2026-09-07
- Registry id: NCT00415233
- Phase: 3
- Setting: Differentiated thyroid cancer needing ablation: low-dose (1.1 GBq) vs high-dose (3.7 GBq) radioiodine, with recombinant TSH or thyroid hormone withdrawal
- Sponsor: Cancer Research UK
- Enrolled: 438
- Result: Ablation success 85.0% (1.1 GBq) vs 88.9% (3.7 GBq), non-inferior.
- Outcomes: Successful ablation: 1.1 GBq 85% vs 3.7 GBq 88.9%
- Replication: ESTIMABL1 (France) replicated low-dose non-inferiority simultaneously.

## Sources

- ClinicalTrials.gov NCT00415233: https://clinicaltrials.gov/study/NCT00415233
- NEJM 2012: https://www.nejm.org/doi/full/10.1056/NEJMoa1109589

## 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: [Cancer Research UK](https://onco.cc/institutions/cruk/)
- drugs: [Radioactive iodine (I-131)](https://onco.cc/drugs/radioactive-iodine/)

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