University of Alberta researchers say they’ve made an important discovery in treating thyroid cancer.
The researchers said patients whose thyroid cancer showed lymph node metastasis at the time of surgery and an extension of the tumour beyond the thyroid, were more likely to be disease-free after five years if they were treated with high-dose radioactive iodine.
Patients with the same two features had a much greater chance of the disease recurring if they were treated with low-dose radioactive iodine, according to the research.
“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,” Todd McMullen, U of A associate professor of surgery and oncology said.
The researchers examined the records of 1,067 thyroid cancer patients at Edmonton’s Cross Cancer institute from 1995 to 2008. Of those patients, 200 with the more aggressive form of the disease were tracked to record 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,” McMullen said.
“That helps guide us in terms of letting us know which patients likely still need higher doses,” Karen Chu, U of A department of oncology assistant clinical professor said.
“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.”
The researchers said one-third of patients need a higher dose of radioactive iodine.
Chu said finding the right balance is critical because too high of a dosage can lead to infertility, permanent dry mouth, dry eyes, bone marrow suppression and a risk of secondary malignancy; while treating patients with too low of a dose initially will lead to more treatments.
“A lot of these patients are young. So they are living with this for a very long time,” Chu said.
“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.”
The researchers said steps are being taken to change clinical practice in Alberta based on the study. They hope new guidelines will be in place for surgeons by the end of the year.