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

International audienceBackgroundPediatric 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. Here, we stratify 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. MethodsAge-standardized incidence rates (ASR) of DTC and annual percent change (APC) in primary DTC rates were estimated among 0-19 year-olds, using data from 39 U.S. cancer registries during 1998-2013. ResultsDuring 1998-2013, 7,296 cases of DTC were diagnosed (6,652 papillary; 644 follicular). ASRs of pediatric DTCs significantly increased by 4.43%/year (95% confidence interval [CI]:3.74, 5.13), primarily due to increases in papillary histologies. Increasing trends were observed for children aged 10-19 years old, for both genders and for non-Hispanic whites, non-Hispanic blacks and Hispanics. Rates increased significantly over the time period for all tumors stages [APClocalized= +4.06%/year (95%CI: 2.84,5.29), APCregional= +5.68%/year (95%CI: 4.64,6.73) and APCdistant= +8.55%/year (95%CI: 5.03,12.19)], and across tumor sizes [APC2cm= +4.69%/year; (95%CI: 2.75,6.67)].ConclusionSignificant increasing rates of DTC over time among 10-19-year-olds in the U.S. are unlikely to be entirely explained by increases in medical surveillance during childhood as rates of large and late stage DTCs are increasing over time. Future studies should examine environmental and other factors that may be contributing to rising DTC rates