Trends in Thyroid Cancer Mortality Rates in Korea: Insights from National Health Database

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Endocrinol Metab. 2024;39(6):853-855

Publication date (electronic) : 2024 December 11

doi : https://doi.org/10.3803/EnM.2024.2251

Division of Endocrinology and Metabolism, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea

Corresponding author: Won Gu Kim. Division of Endocrinology and Metabolism, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea Tel: +82-2-3010-5883, Fax: +82-2-3010-6962, E-mail: wongukim@amc.seoul.kr

Received 2024 November 25; Accepted 2024 December 6.

In the last 20–30 years, the incidence of thyroid cancer has increased significantly around the world. According to recent data from the Global Cancer Observatory (GLOBOCAN), thyroid cancer is now the seventh most common type of cancer type overall and the fifth most common cancer among females [1]. Recent statistics from the Korean Central Cancer Registry reveals that the age-standardized incidence rate of thyroid cancer is the highest among women, at 76.5 cases per 100,000 [2]. For males, it ranks as the fifth most common cancer, with an incidence rate of 24.6 per 100,000 [2]. Due to the issues of over-diagnosis of thyroid cancer, the incidence of thyroid cancer has undergone a dramatic shift. The incidence rate steadily rose until 2012, and it experienced a decline between 2012 and 2015, followed by a relatively stable trend (Fig. 1A). Specifically, the age-standardized incidence rate was 74.83 cases per 100,000 in 2012 but decreased to 42.52 cases per 100,000 by 2015 [3]. Therefore, it is essential to evaluate of the effects of this significant changes on thyroid cancer mortality rates in Korea.

Fig. 1.

Incidence, mortality and case-fatality rate of thyroid cancer in Korea. (A) Age-standardized incidence mortality rates of thyroid cancer in Korea. Adopted from Choi et al. [3,4]. (B) Age-and sex-standardized incidence of thyroid cancer and case-fatality rate in Korea. Adapted from Kim et al. [6]. PY, person-year.

Mortality rate indicates the number of deaths within a specific population over a certain period, typically expressed per 100,000 individuals. Mortality analysis consider the entire population including healthy individuals and those with diseases. Recent data shows that the age-standardized mortality rates for thyroid cancer increased from 0.19 per 100,000 in 1985 to 0.77 per 100,000 in 2002. However, it has since declined steadily to 0.36 per 100,000 in 2020 (Fig. 1A) [4]. Mortality rates in various countries, particularly Europe, have slightly decreased. In 1980, Austria and Switzerland recorded historical rates of around 1.0 per 100,000 females. Since around 2000, these rates have reduced by more than half [5]. A comparative analysis of the Surveillance, Epidemiology, and End Results (SEER) data from the United States reveals differences in thyroid cancer mortality rates. Age-standardized mortality rate rose from 0.44 to 0.54 per 100,000 individuals between 1988 and 2016; however, it decreased to 0.48 per 100,000 by 2020 [4].

Kim et al.’s recent study [6] showed that the mortality rate of thyroid cancer patients steadily declined until 2013, then began to increase again. This study examined thyroid cancer-related mortality using data from the National Health Insurance Service, focusing on a total of 434,228 patients diagnosed with thyroid cancer between 2005 and 2018. The age- and sex-standardized mortality rates for these patients decreased from 1.94 per 1,000 person-year in 2005 to 0.76 per 1,000 person-year in 2013. However, this rate increased again to 2.70 per 1,000 person-years by 2018 (Fig. 1B) [6]. This study is significant as it highlights changes in the fatality rate of thyroid cancer patients after 2013. However, when interpreting the results, it is essential to differentiate between mortality rates in the general population and case fatality rates among thyroid cancer patients. The case fatality rate refers to the proportion of individuals diagnosed with a particular disease who die from that disease within a specific time frame. It reflects the severity or lethality of the disease and focuses solely on diagnosed cases. The increase in the fatality rate of thyroid cancer may indicate a rise in the severity of the disease. Nevertheless, it is crucial to consider that this increase might also due to statistical confounding, stemming from a sharp decline in the incidence of thyroid cancer after 2013.

This study offers several important insights into thyroid cancer mortality. A key factor contributing to the significant rise in thyroid cancer incidence is the increased detection of small papillary thyroid cancer (PTC). This type of cancer is relatively easy to diagnose using ultrasound and typically responds well to treatment. In Korea, PTC has been reported to account for up to 97% of cases [5]. Radioactive iodine-refractory thyroid cancer and anaplastic thyroid cancer (ATC) are the leading causes of death from thyroid cancer. However, they represent less than 5% of cases. ATC is particularly concerning, as most of the cases after inoperable and it often leads to early mortality-typically within 1 year of diagnosis. In contrast, death from other types of thyroid cancer generally occur 2 to 10 years after diagnosis. Consequently, it is fundamentally challenging to analyze when a thyroid cancer patient will pass away based solely on existing cancer registry and mortality statistics. In the study by conducted by Kim et al. [6], researchers examined patient mortality based on the time of thyroid cancer diagnosis, focusing specifically on the 1-year mortality rate. The study found that the 1-year mortality rate for patients diagnosed during the period with the highest incidence of thyroid cancer, from 2012 to 2014, significantly decreased compared to other periods [5]. The mortality rate of patients who did not undergo surgery showed a sharp increase starting from 2013 indicating a greater severity of the disease [5].

Future research on changes in thyroid cancer mortality in Korea should focus on several key points. First, it is necessary to analyze the trends in incidence and mortality according to the pathological types of thyroid cancer. Specifically, evaluation of the incidence and mortality of ATC is crucial, as it significantly impacts early mortality rates. Second, while analyzing patient mortality rates based on the time of thyroid cancer diagnosis is a valuable, it is important to adjust appropriately for changes in incidence at that time. Third, a more detailed analysis of mortality changes concerning surgical interventions and treatment modalities should be conducted. Recent advancements in various targeted therapies have been shown to prolong the time from diagnosis to death in patients with refractory thyroid cancer. Thus, these treatments should be considered when evaluating late mortality in thyroid cancer patients.

Notes

CONFLICTS OF INTEREST

No potential conflict of interest relevant to this article was reported.

Acknowledgements

I would like to thank Prof. Yun Mi Choi and Kyeong Jin Kim for providing the data and for their efforts in creating figure.

References

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