Study found chances of treatment varied widely from hospital to hospital
More than 44,000 people are diagnosed with thyroid cancer annually in the United States, according to the study. When caught early, it is highly treatable by surgically removing the thyroid, and the vast majority of people survive.To kill off any remnants of cancerous tissue, patients are often treated with radioactive iodine.
But the new study finds wide variation from hospital to hospital in the percentage of thyroid cancer patients getting radioactive iodine.
"We found that there was wide variation in the use of radioactive iodine, and the hospital where you received care made a difference in whether or not you received it," said study author Dr. Megan Haymart, an assistant professor of internal medicine at University of Michigan. "Whenever there is so much variation it suggests there is uncertainty -- that physicians are uncertain when radioactive iodine is indicated and when it's not."
The study is published in the Aug. 17 issue of the Journal of the American Medical Association.
Current guidelines recommended radioactive iodine to reduce recurrence in advanced thyroid cancer, including larger tumors and cancer that seems to be moving outside the thyroid. For less advanced, "low- risk" disease, the research isn't there to support the widespread use of radioactive iodine, Haymart said.
To determine how radioactive iodine is being used throughout the nation's hospitals, researchers looked at information from the U.S. National Cancer Database on nearly 190,000 thyroid cancer patients treated at 981 hospitals between 1990 and 2008.
During that period, the use of radioactive iodine increased from about 40 percent of patients in 1990 to 56 percent of patients in 2008.
While patients who had "low-risk" disease (stage 1) were less likely to receive radioactive iodine than patients with advanced thyroid cancer (stage 4), people with stage 2 and stage 3 cancers were just as likely as those with stage 4 tumors to receive the treatment.
The likelihood of receiving radioactive iodine also had a lot to do with where people were treated.
Overall, about 37 percent of women under age 45 with stage 1 tumors received radioactive iodine. But that ranged from 0 percent at some hospitals to more that 90 percent at others.
For a high-risk case -- a man over age 45 with stage 3 or 4 disease, the odds of getting radioactive iodine ranged from 25 percent at some hospitals to 90 percent at others. In this case, the guidelines would call for him to receive iodine treatment.
"The number of patients receiving radioactive iodine has increased significantly, and the researchers find that people with these earliest cancers are getting it with no apparent explanation as to why," said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. "There is a lot of variation in the use of radioactive iodine, which appears to be based more on preferences of the physician, patients or both, than any particular scientific or evidence-based reason."
Radioactive iodine treatment carries some risks, including a slight increase in the chances of getting leukemia or damage to nearby tissue such as salivary glands. Women have to avoid getting pregnant for six months to a year, and have to stay away from young children for about a week after treatment.
"The risk may be relatively minimal, but it's not without some risk," Lichtenfeld said.
But Dr. Edward Livingston, chairman of gastrointestinal and endocrine surgery at University of Texas Southwestern Medical Center, took the research to task, saying that the data doesn't support a conclusion that radioactive iodine is being given inappropriately to low-risk patients
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.
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