US task force recommends against thyroid cancer screening

Miami : Screening for thyroid cancer is not recommended for adults with no symptoms, because there is no evidence it boosts survival and can lead to over-diagnosis and complications, an independent US medical task force said.

"The US Preventive Services Task Force concludes with moderate certainty that screening for thyroid cancer in asymptomatic persons results in harms that outweigh the benefits," said a statement updating the group's 1996 guidelines.

The rate of thyroid cancer has risen faster than any other type of cancer in the last decade in the United States, climbing 4.5 percent per year, said the report in the Journal of the American Medical Association (JAMA).

But the mortality rate from thyroid cancer has not changed substantially, despite the increase in diagnoses.

Often, patients have a good prognosis. More than 98 percent of people diagnosed will survive the first five years.

Experts reviewed 67 studies on the accuracy of screening, whether by ultrasound or by feeling for lumps in the neck, and the benefits and harms of treatment of screen-detected thyroid cancer.

It found "inadequate evidence" to judge the accuracy of either screening technique in people without symptoms.

The panel also found "inadequate direct evidence to determine whether screening for thyroid cancer in asymptomatic persons using neck palpation or ultrasound improves health outcomes."

Any benefit would be small, because thyroid cancer is relatively rare.

The task force did, however find "adequate evidence of serious harms of treatment of thyroid cancer and evidence that over-diagnosis and overtreatment are likely consequences of screening."

An accompanying editorial by Anne Cappola of the Perelman School of Medicine, University of Pennsylvania, pointed to research done in South Korea, where low-cost ultrasonography screening for thyroid cancer was widely offered after 1999.

"Since then, thousands of thyroid carcinomas have been detected, resulting in a 15-fold increase in the diagnosis," she wrote.

"Importantly, the number of deaths from thyroid carcinoma in South Korea during this period has remained unchanged at 300 to 400 per year."

Meanwhile, two percent of patients have reported complications of thyroid surgery, including vocal cord paralysis; and 11 percent emerged with damaged glands numbers she described as "not trivial."

The USPSTF recommendation does not include people at high risk due to having been exposed to radiation in the head or neck in the past.