Fewer thyroid cancers are diagnosed in the United States now than in
the recent past, perhaps signaling a change in physician practices, a
new study says.
And many thyroid growths won't even be called "cancer" any more, according to another new report.
The
tripling of thyroid cancer cases over the past 30 years "used to be a
mystery," said Dr. Luc Morris, lead author of a report published online
April 14 in the journal JAMA Otolaryngology--Head & Neck Surgery.
But
recently, many researchers attributed the rise largely to technological
advances that allow doctors to identify and biopsy small, harmless
nodules in the thyroid gland, said Morris. He is a surgical oncologist
at Memorial Sloan Kettering Cancer Center in New York City.
"Up to
30 percent of healthy persons have small cancers in their thyroid
glands, and nearly all of these would not go on to cause any problems
for the person if the cancer were never discovered," he explained.
They've always been present, "like a huge submerged iceberg, but we are just getting better at finding them," Morris said.
That
explains why the dramatic jump in thyroid cancer is best described as
an "epidemic of diagnosis," not an epidemic of disease, he added.
For
many patients, there would be no benefit -- only potential harm -- in
diagnosing and surgically removing these growths, Morris said.
The thyroid is the gland at the base of your neck.
In the other report, published April 14 in JAMA Oncology,
researchers announced that one type of thyroid cancer has been
reclassified to reflect it is noninvasive and has a low risk of
recurrence.
The name change applies to a tumor known as
encapsulated follicular variant of papillary thyroid carcinoma, which
accounts for 10 to 20 percent of all thyroid cancers diagnosed in Europe
and North America, the researchers noted. Morris said this is among the
tumor types that have led to overdiagnosis in the United States.
The
new name keeps key features to aid pathologists in diagnosis, but
leaves out "cancer," indicating that it need not be treated
aggressively, the study authors said.
"Not only does the
reclassification eliminate the psychological impact of the diagnosis of
'cancer,' it reduces the likelihood of complications of total thyroid
removal, and the overall cost of health care," said the study's senior
investigator, Dr. Yuri Nikiforov. He is professor of pathology at the
University of Pittsburgh School of Medicine.
In the study by
Morris and colleagues, the investigators tracked thyroid cancer cases in
the United States from 1983 to 2012. Incidence increased 3 percent a
year from 1988 to 1998. Over the next decade, the trend more than
doubled, reaching 6.7 percent annually, then leveled off at 1.75
percent, the findings showed.
In the past few years, thyroid
cancer specialists have urged doctors to be more selective about
investigating and biopsying small thyroid nodules, Morris said.
These
recommendations are reflected in national clinical practice guidelines,
such as those of the American Thyroid Association. It's possible the
new findings are a result of those guidelines, he said.
"We infer, but cannot prove, that the leveling off may be due to changes in physician practices," Morris said.
These
findings mirror recent events in South Korea, where incidence of
thyroid cancer skyrocketed due to widespread screening, Morris said.
"Concerned
physicians appealed to the public about overdiagnosis of small thyroid
cancers, leading to a dramatic reversal and an actual drop in thyroid
cancer diagnoses," he said. "We anticipate that a similar course
correction may be beginning in the U.S."
A similar trend has been seen with prostate cancer, said Carol DeSantis, an epidemiologist at the American Cancer Society.
Source--health.usnews
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