A dramatic increase in the thyroid cancer rate across the last 30 years has researchers asking whether the disease’s incidence is truly on the rise, or if improved detection methods are behind the trend.
A study led by a University of North Carolina School of Medicine researcher has found a strong link between increased diagnostic testing and the rise in the thyroid cancer rate. The results were published online in the journal Cancer in November, and were to be published in-print on Sunday.
“This study demonstrates, probably more clearly than before, that the thyroid cancer incidence increase that we’ve seen nationwide is related, most likely, to increased use of thyroid ultrasounds and biopsy,” said Jose P. Zevallos, MD, MPH, FACS, an assistant professor at the UNC School of Medicine Department of Otolaryngology/Head and Neck Surgery and the study’s lead author.
Thyroid cancer, which occurs in a gland at the base of the throat, is the ninth most common cancer in the United States with an estimated 62,980 new cases last year.1 The incidence of the disease has been on the rise, with one study showing the incidence nearly tripling between 1975 and 2009.2
Zevallos said some researchers have argued that better or more frequent tests are picking up on previously undetected thyroid cancers. However, others have suggested that the disease rate has increased for a yet unknown reason.
For the study, researchers analyzed data for veterans who received care through the Veterans Health Administration health system between fiscal years 2000 and 2012. They found that while the thyroid cancer incidence per 100,000 people doubled in that time period, there was a nearly five-fold increase in the use rate of thyroid ultrasound and a seven-fold increase in the fine-needle aspiration biopsy use rate.
That means that the use rates for the tests grew faster than thyroid cancer incidence. While that doesn’t rule out a true increase in thyroid cancer incidence, Zevallos said, it does suggest that over-diagnosis and over-screening are playing an important role in the increased rates of thyroid cancer.
“This study wasn’t designed to demonstrate causality, but it does show a strong link between the use of screening and the increase in thyroid cancer incidence,” he said.
And the problem with over-screening is that health care providers may be detecting small, slow-growing thyroid cancers that would otherwise be clinically insignificant, Zevallos said.
“This may lead to unnecessary treatment including surgery and radioactive iodine therapy,” he said.
Zevallos believes that the increase in the use thyroid ultrasound and biopsy tests may be driven by findings of abnormal thyroid tissue growths in patients undergoing imaging studies such as CT scans for reasons unrelated to thyroid cancer.
“I think that we need to be more judicious in our use of thyroid ultrasound and fine needle aspiration biopsy, and to develop screening protocols targeting individuals at-risk for more aggressive, clinically significant thyroid cancer,” he said.
The study was supported by a Department of Veterans Affairs pilot project grant and also with resources from the VA Health Services Research and Development Center for Innovations in Quality, Effectiveness and Safety at the Michael E. DeBakey VA Medical Center in Houston.
The work was done partly while Zevallos was an assistant professor at the Baylor College of Medicine, but was completed at UNC-Chapel Hill along with collaborators in Houston.
Suggested citation: Zevallos JP, Hartman CM, Kramer JR, Sturgis EM, Chiao EY. 2015. Increased Thyroid Cancer Incidence Corresponds to Increased Use of Thyroid Ultrasound and Fine-Needle Aspiration: A Study of the Veterans Affairs Health Care System. Cancer. 121(5): 1097-0142.
1. National Cancer Institute Surveillance, Epidemiology, and End Results Program. “Seer Stat Fact Sheets: Thyroid Cancer.” Accessed Feb. 27, 2015. http://seer.cancer.gov/statfacts/html/thyro.html.
2. Davies, L, Welch HG. Current thyroid cancer trends in the United States. JAMA Otolaryngol Head Neck Surg. 2014;140:317-322.