WEDNESDAY, May 2 (HealthDay News) -- People with thyroid cancer
are often given a radioactive iodine treatment to wipe out stray
cancer cells, a treatment that comes with its own health risks.
Now, two new studies find that a safer, lower dose of
radioactive iodine is just as effective as the higher dose at
getting rid of any such cells that remain after surgery.
The research also found that patients were just as likely to
have their thyroid shrunk away if they took a drug called Thyrogen
(thyrotropin) as if they underwent thyroid hormone withdrawal --
which leads to fatigue, pain and weight gain -- before embarking on
the radioiodine treatment.
The two studies, published in the May 3 issue of the
New England Journal of Medicine, compared low- and high-dose radioactive iodine in a total of more than 1,000 patients. The participants, from Britain and France, also received either Thyrogen or thyroid hormone withdrawal as part of the therapy.
In either study, the researchers found that patients who
received the low-dose (30 millicuries) of radioactive iodine in
combination with Thyrogen were just as apt to have their remaining
thyroid cells mopped up -- with fewer side effects -- than patients
who received higher-dose (100 millicuries ) radioiodine along with
either Thyrogen or hormone withdrawal.
However, the researchers say they plan on monitoring the
patients for several years to see if rates of cancer recurrence are
similar in the different groups.
"We try to give the lowest possible effective radiation dose so that we cure the current cancer, but we do not increase the risk of producing a second cancer resulting from the radiation itself," explained Dr. Ujjal Mallick, an oncologist at the Northern Centre for Cancer Care in Newcastle upon Tyne, in England, and lead author of the UK study.
Radioactive iodine has been associated with increased risk of a
number of cancers, particularly leukemia, as well as short-term
side effects such as nausea.
"Our study shows that clinicians can consider low-dose radioactive iodine in selected patients that have up to a four-centimeter tumor in the thyroid gland that has not spread outside the neck and have been operated on by expert surgeons," Mallick said.
The number of people diagnosed with thyroid cancer has been on
the rise in the past decade, and there will be more than 56,000 new
cases in the United States in 2012, according to the American
Cancer Society's estimate. The disease, which is highly curable if
caught early, affects more women than men, with patients tending to
be diagnosed in their 40s and 50s.
The new studies suggest that, "we can spare a lot of young
patients by using low-dose radioactive iodine," Mallick said.
However, Dr. David Cooper, an endocrinologist at Johns Hopkins
School of Medicine in Baltimore, said that patients under 45
probably can probably avoid radioactive iodine altogether if their
tumors are small (less than 2 centimeters) and the cancer has not
spread to other parts of their body. Cooper was not involved in the
In fact, some of the low-risk patients in the current studies
might not have needed radioactive iodine treatment at all, Cooper
"The chance that a person with low-risk thyroid cancer is going to come back in a year or two with recurrence is no different whether they got radioactive iodine or not," Cooper said.
In low-risk cases, the whole point of radiation treatment is
more about getting rid of the normal tissue, which makes monitoring
patients for recurrence easier, and less about wiping out disease,
which surgery usually takes care of, Cooper said. However tests are
usually sensitive enough to pick out recurrence even in patients
who do not receive radiation to help eliminate their thyroid.
The research, led by Mallick and his colleagues, involved 421
patients at 29 centers in the U.K. who had thyroid cancer that had
not spread outside the neck. The other study looked at 684 patients
in France who had small thyroid tumors that had not metastasized
(spread) beyond the neck.
All of the patients had undergone surgery to remove the bulk of
their thyroid gland and were receiving thyroid hormone therapy to
replace the natural thyroid hormone.
In both studies, researchers found that the rates of effective
thyroid reduction in the months after treatment were similar in
both the low- and high-dose groups.
Mallick and his colleagues found that about 84 percent of
patients who received low-dose radioactive iodine along with
Thyrogen had undetectable levels of thyroid tissue six to nine
months later, compared with about 90 percent in the
high-dose-plus-Thyrogen group and about 88 percent in the
In addition, the rates of common side effects of radiation such
as neck pain and nausea were higher in the high-dose group than in
the low-dose group.
"These studies are not all that earth shattering" because smaller studies have shown that low-dose therapy is effective, Cooper said. "However these studies add something because they involve hundreds of people that were monitored carefully."
Many doctors in the United States are already using Thyrogen for
thyroid ablation because patients feel awful during the weeks of
thyroid hormone withdrawal leading up to radioactive iodine
therapy, Cooper said.
However, a major problem with radioactive iodine treatment in
the United States is that doctors use it in patients outside of the
2009 American Thyroid Association recommendations, which state that
radioiodine should be used for certain people with tumors larger
than 1 centimeter that have other properties, such as invasiveness,
Cooper said. (Cooper was the lead author of these
The current studies could help doctors at least see that a large
dose of radioactive iodine is not necessary, Cooper said.
For his part, Mallick said, "In our hospital, we are going to
start to implement the low-dose radioactive iodine for patients who
match the criteria in the study."
He and his collaborators are about to start a new trial
comparing low-dose with no radioiodine to see if radiation is
necessary in selected low-risk patients after surgery. "This will
answer a question that has plagued clinicians for several decades,"
To learn more about radioactive iodine, visit the
American Cancer Society.
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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