In both studies, researchers found that the rates of effective thyroid reduction in the months after treatment were similar in both the low- and high-dose groups.
Mallick and his colleagues found that about 84 percent of patients who received low-dose radioactive iodine along with Thyrogen had undetectable levels of thyroid tissue six to nine months later, compared with about 90 percent in the high-dose-plus-Thyrogen group and about 88 percent in the high-dose-plus-hormone-withdrawal group.
In addition, the rates of common side effects of radiation such as neck pain and nausea were higher in the high-dose group than in the low-dose group.
"These studies are not all that earth shattering" because smaller studies have shown that low-dose therapy is effective, Cooper said. "However these studies add something because they involve hundreds of people that were monitored carefully."
Many doctors in the United States are already using Thyrogen for thyroid ablation because patients feel awful during the weeks of thyroid hormone withdrawal leading up to radioactive iodine therapy, Cooper said.
However, a major problem with radioactive iodine treatment in the United States is that doctors use it in patients outside of the 2009 American Thyroid Association recommendations, which state that radioiodine should be used for certain people with tumors larger than 1 centimeter that have other properties, such as invasiveness, Cooper said. (Cooper was the lead author of these recommendations).
The current studies could help doctors at least see that a large dose of radioactive iodine is not necessary, Cooper said.
For his part, Mallick said, "In our hospital, we are going to start to implement the low-dose radioactive iodine for patients who match the criteria in the study."
He and his collaborators are about to start a new trial comparing low-dose with no radioiodine to see if radiation is necessary in selected low-risk patients after surgery. "This will answer a question that has plagued clinicians for several decades," he said.
To learn more about radioactive iodine, visit the American Cancer Society.
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