Medical community does 'about face'

Scientists have long debated what causes thyroid cancer. Once they believed radiation didn’t affect the thyroid; now radiation exposure is the only known cause.

“We thought the thyroid was very resistant to radiation, it was in all of our textbooks 100 years ago,” said Dr. Michael Tuttle, a thyroid cancer specialist at Memorial Sloan Kettering Hospital. “Now if you look at any of the textbooks, we say that the only thing that we know causes thyroid cancer is radiation, it’s like an accepted fact.”

The medical community’s about-face on the effects of radiation came in the 1950s, according to Tuttle, when doctors started seeing an increase in thyroid cancer among teenagers and 20-year-olds.

At that time, skeptics claimed the prevalence of thyroid cancer had not changed. Instead, they argued doctors were reporting the cases and writing about the disease in scientific journals more.

But over a period of about 10 years, researchers figured out radiation – being used to treat children for ailments such as tonsillitis and acne – was causing thyroid cancer.

Radiation, both internal and external, is still the only proven risk factor for thyroid cancer. The evidence: increased thyroid cancer rates among Japanese atomic bomb survivors and survivors of the 1986 Chernobyl nuclear power plant accident.

For Tuttle, who has an interest in radiation-induced thyroid cancer, the present-day debate about the increasing rate is not new.

“[When] everybody started saying it’s all screening, it’s early detection, it reminded me so much of the arguments in the 1950s,” Tuttle said.

There’s a danger in dismissing the increasing rate as a reflection of improved screening.

“If we wouldn’t have looked for a cause, we would have never known that radiation caused thyroid cancer," Tuttle said.

More stories in this investigation: 'We have exposed our kids' | Are you at risk? | Treatment options and outlook | Not just a 'chick's disease' | Thyroid cancer increase baffles researchers | Thyroid 101