Trends in pediatric thyroid cancer incidence in the United States, 1998-2013

Abstract

Background: Pediatric differentiated thyroid cancer (DTC) rates have increased over time in the United States and worldwide. Improvements in imaging for the diagnosis of DTC have been hypothesized as a potential driver of these increases. This study stratifies temporal trends in pediatric DTC by stage and tumor size to assess whether rates of large, late-stage cancers, which are likely to be clinically meaningful, are increasing over time.

Methods: Age-standardized incidence rates (ASRs) of DTC and annual percent changes (APCs) in primary DTC rates were estimated for 0- to 19-year-olds with data from 39 US cancer registries during 1998-2013.

Results: During 1998-2013, 7296 cases of DTC were diagnosed (6652 papillary cases and 644 follicular cases). APCs of pediatric DTCs significantly increased by 4.43%/y [95% CI, 3.74%/y-5.13%/y], primarily because of increases in papillary histologies. Increasing trends were observed for children aged 10 to 19 years for both sexes and for non-Hispanic whites, non-Hispanic blacks, and Hispanics. Rates increased significantly over the time period for all tumor stages (APC_localized , +4.06%/y [95% CI, 2.84%/y-5.29%/y]; APC_regional , +5.68%/y [95% CI, 4.64%/y-6.73%/y]; APC_distant , +8.55%/y [95% CI, 5.03%/y-12.19%/y]) and across tumor sizes (APC_{<1 cm} , +9.46%/y [95% CI, 6.13%/y-12.90%/y]; APC_{1-2 cm} , +6.92%/y [95% CI, 4.31%/y-9.60%/y]; APC_{>2 cm} , +4.69%/y [95% CI, 2.75%/y-6.67%/y]).

Conclusions: Significantly increasing rates of DTC over time among 10- to 19-year-olds in the United States are unlikely to be entirely explained by increases in medical surveillance during childhood because rates of large and late-stage DTC are increasing over time. Future studies should examine environmental and other factors that may be contributing to rising DTC rates.

Keywords: epidemiology; incidence; pediatrics; registries; thyroid cancer.

Figure 1.

Trends in differentiated thyroid cancer incidence by histology, 3-year moving average.

Figure 2.. Trends in differentiated thyroid cancer incidence by age and sex, 3-year moving average.

The error bars that would have crossed the x-axis has been truncated at 2013.

Figure 3.. Trends in differentiated thyroid cancer incidence by tumor size, 3-year moving average.

Study period limited to 2004–2013, when tumor size was routinely collected

Figure 4.. Trends in differentiated thyroid cancer incidence by stage at diagnosis, 3-year moving average.

Analysis limited to the 25 registries that had at least 50% completeness for this variable - 97% known stages. Error bars that would cross the x-axis have been omitted.

Figure 5.

Trends in differentiated thyroid cancer incidence by race and ethnicity