The data used in the analysis isn't detailed enough to know why physicians decided to give the radioactive iodine. Some surgeons may purposefully leave a bit of thyroid tissue to avoid damaging nerves around the gland -- a complication of thyroid surgery -- and then use radioactive iodine to kill the remaining tissue.
"You don't really know enough about what the decision-making was for an individual patient or an individual surgeon," Livingston said.
And there is very little downside to radioactive iodine, he added, with the risk of additional cancers "pretty remote."
To truly compare whether giving radioactive iodine is the best course of treatment in most cases, researchers would need to track outcomes for those who received the treatment and those who didn't over the long-term.
"You really can't look at this intermediate measure of whether they got this iodine or not. You have to look at whether they got cancer again," Livingston said. "Those studies take a long time and they're expensive, but they're worth it because you can only make conclusions about the effectiveness of a particular treatment by knowing that."
On that point, the other experts agreed.
"It all points to the fact that we need better research on thyroid cancer management, so that then the clinical guidelines clearly direct patients and physicians to which patients actually need to radioactive iodine," Haymart said.
The Hormone Foundation has more on thyroid disease.
SOURCES: Megan Haymart, M.D., assistant professor, internal medicine, University of Michigan Medical School, Ann Arbor; Len Lichtenfeld, M.D., deputy chief medical officer, American Cancer Society; Edward Livingston, M.D., chairman, gastrointestinal and endocrine surgery, University o
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