In the United States, the incidence of pediatric thyroid cancer increased more quickly from 2006 to 2013 compared with 1973 to 2006, according to study results published in JAMA Otolaryngology – Head & Neck Surgery.

The results suggest that while rates have increased because of enhanced diagnostic practices, the incidence of thyroid cancer may be increasing in the pediatric population.

The study included participants age <20 years who had a diagnosis of thyroid cancer in the Surveillance, Epidemiology, and End Results 9 database from 1973 to 2013. The researchers used International Classification of Diseases for Oncology, Third Edition codes to identify cases of thyroid cancer, which were then categorized according to histologic type, stage, and tumor size. The researchers used Joinpoint Regression Program analysis to calculate annual percent change (APC) in incidence rates.

The researchers identified 1806 participants with thyroid cancer within the study timeframe, of whom 80.5% were female and 83.2% were white. The overall incidence rate of thyroid cancer increased annually from 0.48/100,000 person-years in 1973 to 1.14/100,000 person-years in 2013.

From 1973 to 2006, the researchers observed a gradual increased incidence rate, with an APC of 1.11% (95% CI, 0.56%-1.67%). From 2006 to 2013, the increase in incidence was significantly more rapid, with an APC of 9.56% (95% CI, 5.09%-14.2%).

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From 1983 to 2006, the incidence of large tumors (>20 mm) increased gradually with an APC of 2.23% (95% CI, 0.93% to 3.54%); from 2006 to 2013, the APC was 8.84% (95% CI, 3.20%-14.8%). The incidence of small tumors (1-20 mm) had an APC of 1.53% (95% CI, 0.11%-2.97%) from 1983 to 2005 compared with an APC of 9.66% (95% CI, 4.81%-17.7%) from 2005 to 2013.

Similar patterns were found when cases were classified as localized or regionally extended thyroid cancers.

Publication of the 2006 American Thyroid Association guidelines, which mentioned pediatric thyroid nodules for the first time, may have led to the increased diagnosis of thyroid cancer, according to the study investigators. “However, the significant increase in large tumors at a rate of 8.84% per year suggests that enhanced diagnosis of small, indolent tumors is not solely responsible for this trend.”

“[C]onsistent with a growing body of work in adult thyroid cancer… A combination of enhanced diagnoses and an actual increase in pediatric thyroid cancer incidence, likely associated with changes in environmental risk factors, may be the main contributors to this trend,” noted the researchers.

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Reference

Qian ZJ, Jin MC, Meister KD, Megwalu UC. Pediatric thyroid cancer incidence and mortality trends in the United States, 1973-2013 [published online May 23, 2019]. JAMA Otolaryngol Head Neck Surg. doi:10.1001/jamaoto.2019.0898