Thyroid cancer patients whose disease is at low risk of returning can be treated safely with a smaller amount of radiation following surgery, according to results from the world's longest running trial to investigate this.

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, told the 2018 NCRI Cancer Conference today (Monday) that the latest results from the HiLo trial showed there was no significant difference in the recurrence rate between patients given a low radiation dose compared to the standard, higher dose.

He said that he said that he wanted to be treated with the drugs, and that he would have the benefit of fewer side effects and long-term complications. He has reported the number of patients with low risk thyroid cancer in the HiLo trial with a medium (average) follow-up time of 6.5 years.

Thyroid cancer cells

The patients were randomized to receive low radioactive iodine activity (RAI) of 1.1GBq, or the standard high RAI of 3.7GBq. They also received either Thyrogen (a genetically-engineered thyroid stimulating hormone, TSH), which stimulates thyroid cancer cells to absorb as much radioactive iodine as possible, making it more effective, or they were asked to stop taking their thyroid hormone tablets, which achieves the same effect by allowing levels of their natural TSH to rise.

Dr Wadsley explained: "Activity is a measure of the amount of radiation that is administered to the patient in the form of a radioactive isotope of iodine. The aim of the 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 to the capsule to swallow."

"As a general principle, we will always wish to give the lowest quantity of possible radiation to prevent the recurrence of thyroid cancer. -term side effects from the treatment, most importantly reducing the risk of the treatment causing another cancer in the future. In our study the lower activity 1.1GB less than the third level of the activity 3.7GBq dose, but has been proven be as effective. "

During the nearly seven years of follow-up, there were 21 recurrences of cancer (11 and 10 with 1.1GBq and 3.7GBq respectively). The recurrence rates were similar between the two doses, and also between patients using Thyrogen or thyroid hormone withdrawal.