Pediatric Thyroid Cancer Incidence and Mortality Trends in the United States, 1973-2013.

Importance: The incidence of thyroid cancer is increasing by 3% annually. This increase is often thought to be attributable to overdiagnosis in adults. A previous study reported a 1.1% annual increase in the incidence of pediatric thyroid cancer. However, the analysis was limited to the period from 1973 to 2004 and was performed in a linear fashion, which does not account for changes in incidence trends over time. Objective: To analyze trends in pediatric thyroid cancer incidence based on demographic and tumor characteristics at diagnosis. Design, Setting, and Participants: This cross-sectional study included individuals younger than 20 years who had a diagnosis of thyroid cancer in the Surveillance, Epidemiology, and End Results (SEER) 9 database from 1973 to 2013. Cases of thyroid cancer were identified using the International Classification of Diseases for Oncology, Third Edition and were categorized by histologic type, stage, and tumor size. Main Outcomes and Measures: Annual percent change (APC) in the incidence rates was calculated using joinpoint regression analysis. Results: Among 1806 patients included in the analysis, 1454 (80.5%) were female and 1503 (83.2%) were white; most patients were aged 15 to 19 years. The overall incidence rates of thyroid cancer increased annually from 0.48 per 100 000 person-years in 1973 to 1.14 per 100 000 person-years in 2013. Incidence rates gradually increased from 1973 to 2006 (APC, 1.11%; 95% CI, 0.56%-1.67%) and then markedly increased from 2006 to 2013 (APC, 9.56%; 95% CI, 5.09%-14.22%). The incidence rates of large tumors (>20 mm) gradually increased from 1983 to 2006 (APC, 2.23%; 95% CI, 0.93%-3.54%) and then markedly increased from 2006 to 2013 (APC, 8.84%; 95% CI, 3.20%-14.79%); these rates were not significantly different from incidence rates of small (1-20 mm) tumors. The incidence rates of regionally extended thyroid cancer gradually increased from 1973 to 2006 (APC, 1.44%; 95% CI, 0.68%-2.21%) and then markedly increased from 2006 to 2013 (APC, 11.16%; 95% CI, 5.26%-17.40%); these rates were not significantly different from the incidence rates of localized disease. Conclusions and Relevance: The incidence rates of pediatric thyroid cancer increased more rapidly from 2006 to 2013 than from 1973 to 2006. The findings suggest that there may be a co-occurring increase in thyroid cancer in the pediatric population in addition to enhanced detection.