Abstract A117: Thyroid cancer incidence trends among pediatrics, adolescents, and young adults in the United States 2001-2015
Authors: Polednik Katherine M. , Simpson Matthew C. , Bukatko Aleksandr R. , Gaubatz Matthew E. , Boakye Eric Adjei , Vavaras Mark A. , Osazuwa-Peters Nosayaba 
Published: August 2020

Abstract
Background: The United States and other industrialized nations are experiencing what is known as the thyroid cancer epidemic. While there are studies of incidence trends among adult thyroid cancer patients in the United States, there is a paucity of data examining the relative contributions of different races/ethnicities and age groups, especially among the pediatric, adolescent, and young adult (AYA) population. This study aimed to identify which racial/ethnic groups may be driving the incidence trends of thyroid cancer among the pediatric and AYA population in the United States.
Methods: We used data from the joint National Program of Cancer Registries/Surveillance, Epidemiology, and End Results databases from 2001 - 2015 (n = 149,578), which covered the entire United States (50 states and the District of Columbia). We calculated age-adjusted incidence rates of thyroid cancer for patients from 0 - 39 years, and rates were stratified by age, race/ethnicity, and sex and presented per 100,000 person-years (PY). Overall rates for the entire study period, rate ratios (RR) with 95% confidence intervals (CI), and annual percent changes (APC) comparing the 2001 rate and 2015 rate were calculated for each group. Joinpoint regression estimated increases/decreases in age-adjusted incidence over time for each group through average annual percent changes (AAPC).
Results: The majority of thyroid cancer patients in this study were females (83%), white (60%), and between 15 - 39 years (98%). The overall incidence was 6.17 per 100,000 PY with an AAPC of 4.22 (p &lt; 0.01). From 2001 to 2015, there was a 79% increase in age-adjusted incidence rate of thyroid cancer pediatric and AYAs in the United States (4.29 per 100,000 PY in 2001 vs. 7.69 per 100,000 PY in 2015). Both pediatric (0-14 years) and AYA (15 - 39 years) groups experienced significant increase in incidence of thyroid cancer in this time period (AAPC for 0 - 14 years = 4.38; AAPC for 15 - 39 years = 4.22; p &lt; 0.01). The AYA population was 34 times as likely to develop thyroid cancer than the pediatric population (RR = 34.55, 95% CI 33.23, 35.94). Also, both males and females experienced significant rate increases from 2001-2015, but females were almost five times (RR = 4.81, 95% CI 4.74, 4.87) as likely to develop thyroid cancer than males (2.13 per 100,000 PY for males vs. 10.26 per 100,000 PY for females). Whites had the highest overall incidence rate (6.87 per 100,000 PY), while blacks had the lowest overall rate (2.89 per 100,000). Compared to whites, all other race/ethnicity groups were significantly less likely to develop thyroid cancer (RR range 0.42 - 0.90). All race/ethnicity groups had significant rate increases from 2001-2015 (AAPC range = 3.69 - 5.70).
Conclusion: Incidence of thyroid cancer increased in both the pediatric and AYA population over the last 15 years, and white females aged 15 - 39 years accounted for most of this increase. These findings can inform future directed screening and reveal unaddressed health disparities.
Citation Format: Katherine M. Polednik, Matthew C. Simpson, Aleksandr R. Bukatko, Matthew E. Gaubatz, Eric Adjei Boakye, Mark A. Vavaras, Nosayaba Osazuwa-Peters. Thyroid cancer incidence trends among pediatrics, adolescents, and young adults in the United States 2001-2015 [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr A117.