Radioactive Iodine Treatment for Children and Young Adults with Thyroid Cancer in South Korea: A Population-based Study

Abstract Purpose This study investigated radioactive iodine treatment (RAIT) patterns and the secondary cancer incidence among children and young adults receiving RAIT after thyroidectomy for thyroid cancer. Methods This population-based cohort study used the Health Insurance Review and Assessment database of South Korea to identify a total of 18 617 children and young adults (0–29 years) who underwent thyroidectomy for thyroid cancer between 2008 and 2018. We recorded age at surgery, sex, the interval from surgery to RAIT, the doses of RAI, the number of RAIT sessions, and secondary cancer incidence. Results A total of 9548 (51.3%) children and young adults underwent 1 or more RAIT sessions. The initial dose of RAIT was 4.35 ± 2.19 GBq. The overall RAIT frequency fell from 60.9% to 38.5%, and the frequency of high-dose RAIT (>3.7 GBq) fell from 64.2% to 36.5% during the observational period. A total of 124 cases of secondary cancer developed during 120 474 person-years of follow-up; 43 (0.5%) in the surgery cohort and 81 (0.8%) in the RAIT cohort. Thus, the RAIT cohort was at an increased risk of secondary cancer (adjusted hazard ratio 1.52 [95% confidence interval 1.03–2.24], P = 0.035). Conclusion The proportion of children and young adults receiving RAIT, and the RAI dose, fell significantly over the observational period. RAIT was associated with secondary cancers. This is of major concern in the context of child and young adult thyroid cancer survivors.