Wed, Jul 15, 2009
Oral Cancer News
Source: HealthDay News
Intensified screening doesn’t entirely explain the jump in thyroid cancers
noted in the United States since 1980, and scientists now believe that other
as-yet-unknown factors are to blame.
A new study finds that thyroid tumors of all sizes are being picked up, not
just the smaller ones that more aggressive screening would be expected to
“You cannot simply explain this by increased screening, there’s a real
increased incidence,” said Dr. Amy Chen, lead author of a study published
online July 13 in the journal Cancer.
Although, “some of this increased incidence is due to increased screening
finding smaller tumors,” she added.
The findings surprised one expert.
“I wrote a chapter about this for a textbook about a year ago and I came
away thinking this [rise in cancers] is a reflection of enhanced
diagnostics,” said Dr. Bruce J. Davidson, professor and chairman of
otolaryngology-head and neck surgery at Georgetown University Hospital in
Washington, D.C. But, “it is more disturbing that it’s not just small
tumors; it seems to be all tumors,” he said.
An estimated 37,200 new cases of thyroid cancer will be diagnosed this year,
according to the U.S. National Cancer Institute. Fortunately, the cancer is
considered highly curable, but the researchers said survival rates have not
improved with better detection.
Until now, an increase in cases seen over the past three decades was
attributed to increased use of ultrasound and image-guided biopsy to detect
tumors. Some researchers had found that thyroid cancer was diagnosed more
often in areas with higher incomes and less in uninsured populations, adding
further credence to this theory.
Looking at thyroid cancer cases from 1988 to 2005 reported in a large cancer
database, Chen and her team found a higher incidence not just in small
tumors, but across all sizes.
The most pronounced increase was seen in primary tumors under 1.0
centimeters ”¹ small ones for which many experts consider it safe to take a
wait-and-see approach. The rate for these tumors rose almost 10 percent per
year in men (1997 to 2005) and 8.6 percent per year in women (1988 to 2005).
But the authors also saw a 3.7 percent annual increase in tumors exceeding 4
centimeters in men and a 5.7 percent yearly rise in these tumors in women.
Cancers that had spread also increased in men by 3.7 percent annually and in
women by 2.3 percent.
Thyroid cancer can be caused by exposure to radiation but there has been no
evidence of increased exposure to radiation among Americans.
“People have looked at background radiation and nothing really has come of
that that’s very useful. And certainly not useful to us in why there would
be a bump in incidence in the last 15 years,” Davidson said.
Chen proposed in the study that environmental, dietary and genetic issues be