Radioactive Iodine Risks May Outweigh Benefit for Some Tumors, Study Finds

The use of radioactive iodine to treat thyroid cancer increased 40 percent from 1990 to 2008 even though the risks may outweigh the benefits for some patients, particularly those with early-stage tumors, researchers said.

About 56 percent of thyroid cancer patients in 2008 were treated with radioactive iodine, which is used after the thyroid is removed to treat residual cancer, compared with 40 percent in 1990, according to a study today in the Journal of the American Medical Association. Determining who gets the treatment doesn’t always depend on how severe the cancer is, researchers found.

Thyroid cancer is the 10th most common cancer in the U.S. with more than 40,000 people diagnosed with the disease each year, according to the study authors. Medical guidelines suggest doctors reserve radioactive iodine for the most aggressive thyroid cancers yet left the option open to physicians for use in patients with less serious tumors, said Megan Haymart, the study’s lead author.

“There are some risks for this, so this rise in use of radioactive iodine coupled with the fact that it’s not being tailored to disease severity is somewhat worrisome,” said Haymart, an assistant professor of internal medicine at the University of Michigan in Ann Arbor. “There need to be more studies on which patients need radioactive iodine.”

The number of people diagnosed with thyroid cancer is rising in the U.S. as doctors find tumors earlier and earlier, she said. Patients with small, low-risk tumors often do fine with just thyroid removal and no radioactive iodine, which can cause secondary cancers and damage to tissues near the thyroid including salivary glands and tear ducts, Haymart said. Patients must also stay away from young children for a week and avoid becoming pregnant for up to a year after treatment.

Cancer Database

Researchers in the study looked at data from 189,219 people diagnosed with thyroid cancer at 981 hospitals between 1990 and 2008 in the National Cancer Database, which captures about 85 percent of the thyroid cancers diagnosed in the U.S.

They found an increase in radioactive iodine use across all tumor types from the least to the most severe.

“For some patients, radioactive iodine is a very important part of treatment, but for others, the risks may outweigh the benefit,” she said in a statement.

Those most likely to receive radioactive iodine were younger, male, had private or government insurance and those without other health conditions, the researchers found. Those with the most aggressive cancer were more likely in the study to receive radioactive iodine than those with stage I. While, those with stages II and III were just as likely as those with stage IV cancer to receive the treatment, the paper found.

Treatment Centers

Patients were also more likely to be given radioactive iodine if they were at hospitals that often treat thyroid cancers, the researchers said.

“Unfortunately many of the treatment centers tend to lump all thyroid cancers together and don’t really individualize their treatment and many patients have an expectation that they need more treatment when in fact they do not,” said Irwin Klein, director of the Thyroid Unit at North Shore University Hospital in Manhasset, New York, in a telephone interview today.

“We’re detecting smaller and smaller thyroid tumors,” said Klein, who was not an author on today’s paper. “While most people agree that surgery is appropriate to remove those tumors, the data out there suggests that these patients don’t need to be treated the way that larger, bulkier tumors are treated with radioactive iodine.”

To contact the reporter on this story: Nicole Ostrow in New York at nostrow1@bloomberg.net.

To contact the editor responsible for this story: Reg Gale at rgale5@bloomberg.net