BACKGROUND
Thyroid cancer is common but usually has an excellent prognosis and, overall, the vast majority of thyroid cancer survivors do not die of the cancer. This is because we have effective treatments, starting with surgery to remove the cancer. If there is concern that there is some cancer left, or if the cancer has spread outside the thyroid, the next step is radioactive iodine therapy. Radioactive iodine is a “magic bullet” as it is taken up and destroys only thyroid cells. In the past, when almost all patients had a total thyroidectomy, most patients were also treated with radioactive iodine therapy. We now have better information to identify patients that are low risk for the cancer to return after the initial surgery. This has led to less surgery (lobectomy, or remove only the lobe containing the cancer) and decreasing the need for radioactive iodine therapy in patients after total thyroidectomy. The newest 2025 ATA guidelines largely restrict the use of radioactive iodine to the high risk of recurrence thyroid cancer group. Using radioactive iodine therapy following total thyroidectomy for thyroid cancer patients currently is controversial for patients who are at low and intermediate risk of recurrence of the cancer.

Making conclusions about how long thyroid cancer patients live (survival) is challenging since there are few studies that look at future outcomes of patients treated in certain way from the beginning. Some studies looking at patients survival might not specify the cause of death. Using study designs with large patient databases are helpful while investigating different types of thyroid cancers and different risk of recurrence thyroid cancers.

The study was done to see if radioactive iodine therapy allowed thyroid cancer patients to live longer.

THE FULL ARTICLE TITLE
Weis H, et al. Impact of radioactive iodine treatment on long-term relative survival in patients with papillary and follicular thyroid cancer: a SEER-based study covering histologic subtypes and recurrence risk categories. J Nucl Med 2025;66:525-530.

SUMMARY OF THE STUDY
Using the SEER medical records database from 2000-2020, 101,087 adult patients with thyroid cancer were studied. The thyroid cancer patients were divided into very low or low risk depending on the cancer size, intermediate risk based on whether there was spread of the cancer to the lymph nodes in the neck, and high risk depending on if the cancer went beyond the thyroid gland or into the lungs or bones. Relative survival compares the observed thyroid cancer patient’s survival to that of a cancer-free patient. The relative survivals of patients who did and did not receive radioactive iodine treatment at years 3, 5, and 10 were compared.

The relative survival of most of the thyroid cancer patients was improved with radioactive iodine therapy. The greatest benefits of the radioactive iodine therapy in papillary thyroid cancers were seen when the cancer was larger, had spread to the lymph nodes, or was otherwise deemed to be a high risk of recurrence cancer. Intermediate risk of recurrence thyroid cancer patients benefitted in survival by 1-2% with radioactive iodine therapy. High risk of recurrence thyroid cancer patients benefitted in survival by over 10% with radioactive iodine. For patients with follicular thyroid cancer at high risk of recurrence, the survival benefit at 10 years was 30.9%. There was trend of survival benefit even in low risk of recurrence, minimally invasive follicular thyroid cancer patients.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study suggests that radioactive iodine therapy might help patients live longer who have different types of thyroid cancers. The biggest survival benefit of radioactive iodine therapy was seen in patients who were diagnosed with intermediate and high risk of recurrence papillary thyroid cancers and follicular thyroid cancers, even if minimally invasive. Radioactive iodine therapy was not found to limit survival in any of the thyroid cancer patients. Some elderly patients diagnosed with thyroid cancer might pass away from other reasons, but in previous studies the cause of death might not have been specified. This study shows that it is important to follow thyroid cancers for many years to see the survival benefit of radioactive iodine treatment.

— Pinar Smith, MD

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