Pediatric differentiated thyroid cancer (DTC) has been on the rise. The past 2 decades have seen an increased incidence in the United States and worldwide. The question is why — and this is the riddle that a team led by Marie-Odile Bernier, MD, PhD, an epidemiologist at the Institute of Radioprotection and Nuclear Safety in France, sought to unravel in their paper.1

To understand whether the increase is clinically meaningful, Dr Bernier’s team analyzed the age-standardized incidence rate of DTC and estimated the annual percent change from 1998 to 2013. By determining which tumor types increased during this time span (and among which populations), the researchers hoped to discern whether the spike was due to screening practices — and therefore, likely could be explained as overdiagnosis — or some other factor.

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According to their report, published in Cancer in April 2019, the DTC incidence rate among individuals aged 0 to 19 years rose 4.43% every year from 1998 to 2013.1 The authors observed the strongest increasing trends among children aged 10 to 19 years, across all races and genders. And the numbers increased for all tumor stages and sizes, albeit at different rates.

To Dr Bernier, the data cannot be entirely explained by changing screening practices. The fact that both large and small tumors markedly increased, said Dr Bernier, means that overdiagnosis — detection of a tumor due to expanded cancer screening that otherwise would have gone unnoticed, but is not likely to cause harm — also can’t account for the rise. “We suspect an environmental impact,” noted Dr Bernier.