Long-Term Trends in Thyroid Cancer Incidence and Mortality in Korea: Analysis of Korean National Data

The incidence of thyroid cancer in Korea increased rapidly for decades and started declining around the mid-2010s. However, the mortality rate is stable without significant changes. This study evaluated the long-term trends in the standardized incidence rate/standardized mortality rate (SIR/SMR) of thyroid cancer in Korea.

Cancer-specific incidence data from 1999 to 2021 and mortality data from 1985 to 2023 were obtained from Statistics Korea. SIR and SMR were calculated using the 2000 and 2005 Korean mid-year resident registration populations, respectively, as the standard populations. Trends in incidence and mortality were further analyzed using joinpoint regression analysis.

The SIR was 7.41 per 100,000 in 1999, which peaked at 75.06 in 2012. It then decreased to 42.50 by 2015, but subsequently increased to 60.13 in 2021. SIR patterns tend to vary by age and sex. Stage-specific analyses revealed a renewed increase in both localized and distant stage cancers from 2015 onwards. Histologically, the incidence of papillary carcinoma decreased after 2010, whereas that of follicular carcinoma and medullary carcinoma showed recent upward trends. The SMR increased until the early 2000s but has since steadily declined, with the trend most evident among those aged ≥55 years.

The incidence of thyroid cancer in Korea peaked in 2012, decreased until 2015, and has since modestly increased, particularly among men, younger adults, and patients with follicular, localized, or distant-stage disease. Thyroid cancer mortality has continually declined since the early 2000s. Continuous long-term monitoring is required to assess the effects of changes in clinical and diagnostic practices.