Pediatric Thyroid Carcinoma Incidence and Temporal Trends in the USA (1973–2007): Race or Shifting Diagnostic Paradigm?

Pediatric thyroid carcinoma is relatively uncommon. But variability in incidence rate by race, sex, age at onset/diagnosis, and geographic local had been observed in adult thyroid carcinoma in the USA. We aimed to examine the patterns, rates, and temporal trends of thyroid carcinoma among pediatric patients (0-19 years) between 1973 and 2007. The Surveillance, Epidemiology, and End Results (SEER) data of the National Cancer Institute were utilized. Data were available on sex, age at diagnosis, race/ethnicity, and geographic locale (9 SEER registries) and were used for rates and trends computation. The frequency and percentage, percent changes (PCs) were calculated by using 1 year of each endpoint. Similarly, the annual percent changes (APCs) were calculated as well, with APCs estimated using weighted least square methods. Between 1973 and 2007, 1,360 thyroid cancer cases were ascertained in the 9 SEER areas (n = 247,638,734) in the USA. The percent change was 47.9, while the APC was significantly different from 0, 1.0 (95% CI: 0.5-1.6, P < 0.0001). The rate ratio (RR) was significantly lower in 1975 (RR: 0.62, 95% CI: 0.38-0.98, P = 0.03) relative to the rate between 1973 and 2007 (RR: 1.60, per 100,000, 95% CI: 1.50-1.70), but higher in 2007 (RR: 2.3 per 100,000, 95% CI: 1.70-3.10; RR: 1.44, 95% CI: 1.05-1.93, P = 0.02). The rate was significantly higher in whites relative to blacks, highest among age group of 15-19 years and girls, and in some SEER registries, with some significant PC in Connecticut. This temporal trend study of pediatric thyroid carcinoma indicates increase in the rate of this malignancy given the percent change and the annual percent change between 1973 and 2007. In addition, the incidence was higher among girls, lower among blacks, highest in age group of 15-19 years, and relatively higher in SEER registries with predominantly white or Hispanic populations.