BACKGROUND
Thyroid cancer is common in adults and children. Most patients do very well as there are effective treatments for thyroid cancer. Surgery is the first option and is often curative. For patients with high risk thyroid cancer, radioactive iodine therapy can be very helpful as it seeks out thyroid cancer cells remaining after surgery and destroys them. There are some potential long-term problems associated with radioactive iodine therapy, especially for children. For example salivary gland damage leading to dry mouth, getting other cancers later in life and possibly having trouble having kids in the future. Partly because of this, as well as the fact that patients with low risk thyroid cancer do well with surgery alone, the most recent American Thyroid Association guidelines to treat thyroid cancer in children no longer recommend radioactive iodine therapy for those with low risk cancer.

The researchers designed this study to find out if doctors changed how they treated the children with low-risk thyroid cancer after the change in the guidelines. They also wanted to find out if not giving radioactive iodine therapy had any effect on thyroid cancer recurrence in children.

THE FULL ARTICLE TITLE
Bojarsky M, et al. Outcomes of ATA low-risk pediatric thyroid cancer patients not treated with radioactive iodine Therapy. J Clin Endocrinol Metab 2023;108(12):3338- 3344; doi: 10.1210/clinem/dgad322. PMID: 37265226.

SUMMARY OF THE STUDY
The study was done at Children’s Hospital of Philadelphia. The researchers reviewed the medical records of patients who were less than 19 years old when they were treated for low-risk thyroid cancer between 2010 and 2020. Low risk patients had thyroid cancer only in their thyroid gland and not in the nearby lymph nodes, or if they had cancer in the lymph nodes it was a very small amount in less than 5 nodes. They looked at blood tests for a protein called thyroglobulin which only comes from thyroid cells, checked for antibodies related to it, and did ultrasound scans of the neck to see how well the treatments worked. They split the results into 4 groups: 1) excellent response if there was no sign of cancer with the blood tests or the ultrasound, 2) biochemical incomplete response if the thyroglobulin levels remain detectable, 3) structural incomplete response if the ultrasound found something abnormal and 4) indeterminate response if they were not sure yet.

They also checked for some changes in the genes that might be linked to cancer especially more aggressive cancer. They analyzed the results to find out the things that had influenced whether patients got radioactive iodine therapy or if their cancer went away.

They looked at 95 patients who had low-risk thyroid cancer, 78 girls and 17 boys. Out of these, 53% got treatment with radioactive iodine therapy and 47% didn’t. Radioactive iodine therapy was more commonly used before 2015, 82% of patients before 2015 and only 33% of patients after 2015 were treated with radioactive iodine therapy. Patients who had larger cancers, cancer in the lymph nodes and who were treated before 2015 were more likely to have radioactive iodine therapy. About 70% of patients who were treated with radioactive iodine therapy and 69% of those who didn’t were doing very well after 1 year so there wasn’t much difference. As time passed even more of them started to do well without any sign of cancer. None of the patients had persistent structural disease. There wasn’t a big difference in the rate of improvement after one year and at the last check up between patients with genes that could make the cancer more aggressive and those with genes that are less likely to make it worse regardless of radioactive iodine therapy.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
The authors concluded that not giving radioactive iodine therapy to children with low-risk thyroid cancer doesn’t affect their prognosis. One year after treatment is a good time to check how the cancer is doing to see if not giving radioactive iodine therapy has affected their chances of getting better. The findings of this study are important for patients because they support the recent recommendations in how we treat low-risk thyroid cancer in children and confirms that it is safe and equally effective to avoid radioactive iodine therapy in these patients. We still need the results from continuation of this and similar studies that follow the patients for longer periods to make sure cancer does not come back.

— Ebru Sulanc, MD

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