Low Dose Radiation Prevents Recurrence in Low-Risk Thyroid Cancer Patients

Highlights:

Patients at low-risk of thyroid cancer recurrence can be safely treated with low dose radiation compared to the currently followed standard dose
Low dose radiation is equally effective and associated with fewer side effects and complications and additionally, more cost-effective for healthcare services
Based on these findings, international guidelines may be updated to recommend treating low-risk thyroid cancer patients with a low dose as against the current higher standard dose radiation

A lower dose of radiation, in other words, administration of low radioactive iodine activity (RAI) treatment, is safe and effective for patients with low risk of thyroid cancer recurrence, according to the longest running clinical trial in the world, the HiLo trial conducted in the UK. The results of the trial were presented at the National Cancer Research Institute (NCRI) Cancer Conference 2018.

Until now, research data was insufficient and follow-up duration of patients was shorter in previous trials to make strong recommendations to change the existing international guidelines to manage low risk thyroid cancer. The HiLo trial had a mean patient follow-up duration of 6 ½ years.

According to Dr Jonathan Wadsley, a consultant clinical oncologist at the Weston Park Hospital, Sheffield, UK, and chair of the National Cancer Research Institute (NCRI) Thyroid Cancer Subgroup, "Now that we have confirmation that there is no difference in recurrence rates over a longer follow-up period, these recommendations can be strengthened and clinicians and patients can be confident that the use of the lower activity is acceptable and in fact preferable."

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‘Based on the findings of the HiLo trial, international guidelines may be updated to recommend treating low-risk thyroid cancer patients with lower doses of radiation in future.’
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Assessment of Low Vs High Dose Radiation in Low-Risk Thyroid Cancer

The HiLo trial assessed the efficacy of low vs high dose radiation in treating low-risk thyroid cancer patients
The study included 434 participants with low-risk thyroid cancer who were monitored for an average period of 6 ½ years
The participants were randomly assigned to receive either low radioactive iodine activity (RAI) of 1.1GBq or the standard high RAI of 3.7GBq
Patients additionally received either Thyrogen (a genetically-engineered thyroid stimulating hormone, TSH), or they advised to stop taking thyroid hormone tablets (which allows levels of their natural TSH to rise). The increased TSH levels induced thyroid cancer cells to absorb as much radioactive iodine as possible, making treatment more effective

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Findings of Study

In the approximately seven years of follow-up, 21 cancer recurrences (11 and 10 with 1.1GBq and 3.7GBq respectively) were noted.
The recurrence rates were found to be similar for both the doses, as well as between patients using thyroid hormone withdrawal or Thyrogen

Additionally, the quality of life and ability to return to a normal routine was higher among patients who received Thyrogen compared to thyroid hormone withdrawal.

Says Dr. Wadsley, “The aim of radiation treatment is to destroy any residual normal thyroid tissue and thyroid cancer cells following surgery to remove the thyroid gland. The treatment is most commonly given as a capsule to swallow. As a general principle, we would always wish to give the lowest quantity of radiation possible to prevent the recurrence of thyroid cancer. This is to reduce the risk of longer-term side effects from the treatment, most importantly reducing the risk of the treatment causing another cancer in the future. In our study, the low activity 1.1GBq dose was less than a third of the higher activity 3.7GBq dose, but has been proven to be as effective."

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Advantages of Lower Radiation Dose in Thyroid Cancer

Lower incidence of nausea and feeling sick during treatment
Reduced risk of damage to salivary glands which results in permanent dry mouth
Reduced duration of treatment and hospital stay
No need for patient isolation which is required for the higher dose
Better quality of life later due to reduced radiation exposure
Decreased cost for healthcare service systems

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Future Research Plans

Following this study, the team plans to investigate whether a group of patients identified as very low risk of recurrence of their thyroid cancer can be avoided giving radioiodine treatment.

The IoN trial (Iodine or Not) randomly assigns patients with very low risk thyroid cancer either to have radioiodine therapy or just close observation to find if there is any difference in recurrence rates.

Conclusion

To conclude with the remarks of Dr Martin Forster from University College London, and also chair of the NCRI Head and Neck Clinical Studies Group and was not part of this study, “The HiLo trial is a good example of a well-conducted clinical trial that can make a real difference to the quality of life for these (low risk thyroid cancer) patients.”

Reference:

Recurrence rates after low dose radioiodine ablation for differentiated thyroid cancer within the NCRI HiLo trial. - (http://abstracts.ncri.org.uk/abstract/recurrence-rates-after-low-dose-radioiodine-ablation-for-differentiated-thyroid-cancer-within-the-ncri-hilo-trial/)

Source-Medindia