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.

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.

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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.

Although Bernier noted that DTC is too rare to warrant public health attention, she is concerned that the rules governing childhood exposure to radiation may need adjustment.

Other recent work supports the notion of an environmental cause. A study led by Uchechukwu Megwalu, MD, MPH, a head and neck specialist at Stanford University, California, in the May 2019 issue of JAMA Otolaryngology-Head and Neck Surgery, also suggested that the rising prevalence from 2006 to 2013 cannot be explained by enhanced detection of small, early-stage tumors alone; the marked increases in the incidence of large tumors and advanced-stage disease “suggest a true increase in the occurrence of pediatric thyroid cancer in the United States.”2 The change, according to Dr Megwalu, “is fairly alarming.”

Other experts aren’t so sure. In an editorial accompanying Dr Bernier’s report, Amy Chen, MD, MPH, an otolaryngologist at Emory University, Atlanta, Georgia, and Louise Davies, MD, MS, an otolaryngologist and health outcomes researcher at The Dartmouth Institute for Health Policy & Clinical Practice, New Hampshire, focus on overdiagnosis as the major culprit.3 They cite the screening program undertaken by the Japanese government following the Fukushima nuclear power plant accident in 2011, which led to a massive increase in pediatric DTC that could be entirely attributed to the screening. They contradict the assertion by Dr Bernier’s team that overdiagnosis is a phenomenon in adult cancer only, noting that between 1996 and 2010, the use of computed tomography for pediatric patients more than doubled — and more imaging means more diagnoses.

In a second editorial, David Goldenberg, MD, a head and neck surgeon at Pennsylvania State University College of Medicine, Hershey, agrees with Dr Bernier: “Increased scrutiny,” he wrote, “does not fully explain the rise in thyroid cancer.”4 Dr Goldenberg suggested several possible alternative explanations for the increase in incidence, including obesity, reproductive issues, and improved iodine nutrition.

References

  1. Bernier MO, Withrow DR, Berrington de Gonzalez A, et al. Trends in pediatric thyroid cancer incidence in the United States, 1998-2013 [published online April 23, 2019]. Cancer. doi: 10.1002/cncr.32125
  2. Qian ZJ, Jin MC, Meister KD, Megwalu UC. Pediatric thyroid cancer incidence and mortality trends in the United States, 1973-2013. JAMA Otolaryngol Head Neck Surg. doi: 10.1001/jamaoto.2019.0898
  3. Chen AY, Davies L. Children and thyroid cancer: interpreting troubling trends [published online April 23, 2019]. Cancer. doi: 10.1002/cncr.32124
  4. Goldenberg, D. We cannot ignore the real component of the rise in thyroid cancer incidence [published online April 23, 2019]. Cancer. doi: 10.1002/cncr.32123

This article originally appeared on Oncology Nurse Advisor