Walking a fine line: Research spurs doctors to re-examine treatment for thyroid cancer

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(Photo Credit: Online Cancer Guide)

Research from the University of Alberta spurs doctors to re-examine how they treat patients with thyroid cancer.

Researchers found patients whose thyroid cancer showed two key features—lymph node metastasis at the time of surgery and an extension of a tumour beyond the thyroid—were much more likely to be disease-free after five years if they were treated with high-dose radioactive iodine. Patients with those same features had a much greater chance of the disease recurring if they were treated with low-dose radioactive iodine.

According to McMullen, a major predicament that faces surgeons is determining which patients will benefit from less aggressive treatment and which ones need high-dose radioactive iodine.

“The evidence was so compelling based on what we saw that we think it’s appropriate that we examine our own local guidelines and look at it in Alberta right away,” says Todd McMullen, an associate professor of surgery and oncology at the U of A and an endocrine surgeon at the U of A Hospital who participated in the study.

According to McMullen, a major predicament that faces surgeons is determining which patients will benefit from less aggressive treatment and which ones need high-dose radioactive iodine.

To get to the bottom of it, researchers examined the records of 1,067 thyroid cancer patients at Edmonton’s Cross Cancer Institute from 1995 to 2008. Of those, approximately 200 patients with the more aggressive form of the disease were monitored over a duration of time based on how much radioactive iodine they were treated with.

“We found there were probably three or four times more recurrences in patients that had low dose as compared to high dose,” says McMullen.

“That helps guide us in terms of letting us know which patients likely still need higher doses,” adds Karen Chu, an assistant clinical professor with the U of A’s Department of Oncology who led the study.

The right balance is key in determining the proper iodine dose according to the researchers. Approximately one-third of patients will need a higher dose of radioactive iodine.

“The more radioactive iodine we give, the more likely they’re going to have long-term complications. If we can find the right dose so we only treat them the one time, in hopes that is the cure, then they would not need to have more treatments afterwards and won’t have all the long-term side-effects,” she explains.

The right balance is key in determining the proper iodine dose according to the researchers. Approximately one-third of patients will need a higher dose of radioactive iodine. It walks a fine line: too high of an overall lifetime dose can lead to infertility, permanent dry mouth, dry eyes, bone marrow suppression and a risk of secondary malignancy; too low of a dose initially will lead to additional treatments in the future, meaning more radioactive iodine in the long run.

“A lot of these patients are young. So, they are living with this for a very long time. If we don’t have to treat them a second time, or a third time or a fourth time, that is the best way to go,” says Chu, who is also a radiation oncologist at the Cross Cancer Institute.

The team is hoping to expand on its findings through a potential multi-centre clinical trial in the future. McMullen and Chu say that steps are already being taken to change clinical practice in Alberta based on the research. They hope new guidelines for surgeons will be in place by the end of 2018.

“These are things we already monitor for,” says McMullen. “That’s why we can change what we do relatively quickly. It’s just a question of putting the protocols in place.”

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