Thyroid cancer-specific mortality during 2005–2018 in Korea, aftermath of the overdiagnosis issue: a nationwide population-based cohort study

Abstract

Background: Thyroid cancer (TC) has underwent notable changes in its diagnosis and treatments following the concerns regarding overdiagnosis and overtreatment. However, there is little research on evaluating the effects of these alterations on TC-specific mortality. Materials and methods: This population-based cohort study included 434 228 patients with TC using Korean National Health Insurance Service-National Health Information Database. The age-standardized and sex-standardized mortality rates of TC per 1000 person-years were calculated considering the number of patients diagnosed with TC in 2013 per our database to evaluate the TC-specific mortality trends according to the year of TC diagnosis. Results: The authors enrolled 434 228 patients with TC, including 352 678 women and 81 550 men, with a mean age of 48.6±12.5 years and a median follow-up duration of 7.4 (interquartile range: 4.5–10.1) years. TC incidence increased from 2005 to 2012, with a standardized rate of 91.9 per 100 000 people in 2012, decreased rapidly to 50.6 in 2015, and remained stable until 2018. However, TC-specific age-standardized and sex-standardized mortality rates decreased from 1.94 per 1000 person-years in 2005 to 0.76 per 1000 person-years in 2013 and then increased to 2.70 per 1000 person-years in 2018. The TC-specific age-standardized and sex-standardized mortality rates of patients who had undergone hemithyroidectomy or subtotal thyroidectomy remained steady during 2005–2018, but increased in patients who had undergone total thyroidectomy or not undergone thyroidectomy between 2013 and 2018. Conclusions: The TC-specific mortality rates among patients with TC diagnosed since 2015 have increased, in contrast to the significant decline in TC incidence during the same period. This underscores the importance of appropriate diagnosis and treatment in patients with TC at high-risk of progression, simultaneously emphasizing efforts to reduce overdiagnosis and overtreatment in those with low-risk TC.