Low-risk thyroid cancer patients can safely forgo radioactive iodine treatments

The thyroid uses iodine, a mineral found in some foods and in iodized salt, to help make several hormones that control heart rate, body temperature and metabolism. – Image credit: National Cancer Institute

CANCER DIGEST – June 22, 2025 – Thyroid cancer patients with low risk of recurrence can safely forgo radioactive iodine treatment following surgery, a new study by researchers at the University College London, UK, shows.

The study was published in the June 18, 2025 The Lancet and was led by Ujjal Mallick, FRCR. It involved 504 patients with low-risk thyroid cancer, half of whom were treated with radioactive iodine after surgery, and half were treated with surgery alone.

The standard treatment for thyroid cancer has been to follow surgery with radioactive iodine as a way to prevent recurrence. Thyroid cancer affects about 44,000 people in the U.S. each year according to the American Cancer Society. 

Because the thyroid absorbs nearly all the iodine that enters the body, thyroid cancer patients are routinely given one or two doses of radioactive iodine to eliminate any remaining cancerous thyroid cells missed by surgery. Patients are usually kept in the hospital or clinic for a day or more to ensure the patient doesn’t expose others to radiation.

In the clinical trial, participants were randomly assigned to have radioactive iodine after surgery or surgery alone. Patients were monitored with monthly examination of thyroid serum samples and annual neck ultrasound scans. 

After five years the researchers looked at cancer recurrence rates. Among the surgery plus iodine treatment 96.3 percent had no recurrence compared to 97.9 percent of the surgery alone group. The difference was considered insignificant, meaning it could have been due to chance.

The significance of the finding is that patients with low-risk thyroid cancer no longer need to spend time in a hospital or clinic while receiving the radiation therapy, and can be spared the side effects of that therapy. 

“This is particularly important because around a third of patients in the study were aged 40 years or less, and many would have children to care for," Professor Allan Hackshaw, senior author of the study said in a press release. "Not having physical contact can be quite hard for them. Being spared radioactive iodine therapy means they will be able to get back to a near normal life much more quickly, as well as receiving the emotional and physical support of their families in the weeks after their operation.”

The study confirms results of an earlier trial but would double the number of eligible patients estimated by the previous trial who could forgo the radiation treatment.

Sources: University College London press release, and The Lancet.