Reasons Behind Climb in Thyroid Cancer

Thyroid cancer detection methods did not show difference in disease characteristics

(RxWiki News) Thyroid cancer is on the rise in the US. Scientists can’t say exactly why this is happening. One theory is that improvements in imaging technologies are picking up more thyroid cancers during tests for other conditions.

A new study found that there were no biological differences in thyroid cancer based on the way it was detected.

Tumor type, size and rate of spread were essentially the same, regardless of whether the thyroid cancer was revealed through targeted testing or by accident during imaging for other diseases.

As a result of these findings, the researchers suggested that imaging technology is not the reason behind the rising rates of thyroid cancer.

"Ask your doctor about the type of imaging tests you’ll receive."

Frederick Yoo, MD, and colleagues at Penn State College of Medicine/Penn State Milton S. Hershey Medical Center in Hershey, PA, and colleagues wanted to compare the characteristics of thyroid cancers detected incidentally (ID), or found by chance while testing for other diseases, and nonincidentally (NID).

The number of cases of thyroid cancers has increased over the past 30 years, going from 4.9 cases per 100,000 people in 1975 to 14.3 per 100,000 in 2009.

An estimated 66,200 Americans will be diagnosed with thyroid cancer this year.

Researchers have argued that improved imaging picks up more thyroid cancers and is the cause for the increase in rates.

This research team theorized that if technology is behind the rise, cancers found incidentally would be smaller and picked up at an earlier stage.

A total of 238 thyroid cancer patients were identified for this study — 31 who were diagnosed incidentally and 207 whose cancers were detected through specific tests.

The researchers found that the age at diagnosis was 56 in the ID group and 42 in the NID group.

The researchers compared the tumor type (pathology) and size, along with the extent of thyroid cancer metastasis (spread) seen in both groups.

People in the ID group tended to have more high-risk disease than folks who were diagnosed with specific tests (22 percent versus 12.6 percent). But that finding and age at diagnosis were the only key differences.

“We found no significant difference between the tumor characteristics and tumor behavior of ID and NID thyroid cancers. Specifically, pathology [type], tumor size, rate of local invasion, and rate of regional and distant metastasis did not differ between ID and NID thyroid cancers,” the authors wrote.

“This may imply that the overall elevation in the incidence of thyroid cancer is not solely due to the heightened diagnosis of incidental cancer and may represent a true rise in incidence,” the study concluded

This study was published online October 10 in JAMA Otolaryngology–Head & Neck Surgery.

No outside funding or conflicts of interest were reported.

Review Date: 
October 10, 2013