Recent Changes in the Incidence of Thyroid Cancer in Korea between 2005 and 2018: Analysis of Korean National Data

Thyroid Cancer Incidence Among Korean Individuals: A Comparison of South Korea and the United States

OBJECTIVE

To compare thyroid cancer incidence rates and trends between Korean, non-Korean Asian, and non-Hispanic White populations in the United States, and between the US Korean population and the South Korean population.

METHOD

Population-based analysis of cancer incidence data. Cases of thyroid cancer diagnosed during 1999-2014 from the Korean Central Cancer Registry (KCCR) and the Surveillance, Epidemiology, and End Results (SEER) 9 detailed Asian/Pacific Islander subgroup incidence and population dataset were included. Incidence rates were obtained from the datasets, and annual percent change (APC) of the incidence rates was calculated using Joinpoint regression analysis.

RESULTS

Thyroid cancer incidence rate for 1999-2014 was significantly higher for South Korea (48.05 [95% CI 47.89-48.22] per 100,000 person-years) than for the US Korean population (11.12 [95% CI 10.49-11.78] per 100,000 person-years), which was slightly higher than the Non-Korean Asian population (10.23 [95% CI 10.02-10.43] per 100,000 person-years), and slightly lower than the Non-Hispanic White population (12.78 [95% CI 12.69-12.87] per 100,000 person-years). Incidence rates in South Korea increased dramatically (average APC 17.9, 95% CI 16.0-19.9), significantly higher than the US Korean population (average APC 5.0, 95% CI 3.1-6.8), which was similar to the non-Korean Asian (average APC 2.5, 95% CI 0.9-4.2) and the non-Hispanic White (average APC 5.1, 95% CI 4.7-5.6) populations.

CONCLUSIONS

South Korea's high thyroid cancer incidence rates cannot be attributed to genetic factors, but are likely due to health care system factors.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:4156-4160, 2024.

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

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.

Association between Consumption of Iodine-Rich Foods and Thyroid Cancer Prevalence: Findings from a Large Population-Based Study

The influence of iodine-rich foods on thyroid cancer (TC) risk remains inadequately understood. Therefore, we aimed to comprehensively investigate the relationship between three iodine-rich food groups and TC prevalence using extensive data from a large Korean population. We assessed the dietary intake of 169,057 participants in the Korean Genome and Epidemiology Study (2004-2013) using a food frequency questionnaire. The top-three iodine-rich food groups (including egg, seaweed, and dairy) were selected based on Korean dietary reference intakes and categorized by weekly consumption frequency. We conducted multiple logistic regression models to examine the relationship between food consumption and TC prevalence. After adjusting for confounding factors, higher seaweed consumption (>5 times/week) was significantly associated with lower TC prevalence (odds ratio [OR], 95% confidence interval [CI] = 0.42, 0.32-0.56, p-value < 0.001). In contrast, compared with moderate dairy consumption (3-4 times/week), lower dairy product intake (<1 time/week) was associated with higher TC prevalence (OR, 95% CI = 1.32, 1.05-1.67, p-value = 0.017). Our findings suggest that sufficient seaweed consumption may offer protection against TC, and incorporating dairy products into the diet may lower TC incidence in the Korean population. The most significant limitations of our study are the absence of 24 h urine samples for iodine status assessment and the lack of clinical data on the diagnosis of thyroid cancer.

Contents analysis of thyroid cancer-related information uploaded to YouTube by physicians in Korea: endorsing thyroid cancer screening, potentially leading to overdiagnosis

BACKGROUND

Thyroid cancer overdiagnosis is a major public health issue in South Korea, which has the highest incidence rate. The accessibility of information through the Internet, particularly on YouTube, could potentially impact excessive screening. This study aimed to analyze the content of thyroid cancer-related YouTube videos, particularly those from 2016 onwards, to evaluate the potential spread of misinformation.

METHODS

A total of 326 videos for analysis were collected using a video search protocol with the keyword "thyroid cancer" on YouTube. This study classified the selected YouTube videos as either provided by medical professionals or not and used topic clustering with LDA (latent dirichlet allocation), sentiment analysis with KoBERT (Korean bidirectional encoder representations from transformers), and reliability evaluation to analyze the content. The proportion of mentions of poor prognosis for thyroid cancer and the categorization of advertising content was also analyzed.

RESULTS

Videos by medical professionals were categorized into 7 topics, with "Thyroid cancer is not a 'Good cancer'" being the most common. The number of videos opposing excessive thyroid cancer screening decreased gradually yearly. Videos advocating screening received more favorable comments from viewers than videos opposing excessive thyroid cancer screening. Patient experience videos were categorized into 6 topics, with the "Treatment process and after-treatment" being the most common.

CONCLUSION

This study found that a significant proportion of videos uploaded by medical professionals on thyroid cancer endorse the practice, potentially leading to excessive treatments. The study highlights the need for medical professionals to provide high-quality and unbiased information on social media platforms to prevent the spread of medical misinformation and the need for criteria to judge the content and quality of online health information.

Cost-Utility Analysis of Early Detection with Ultrasonography of Differentiated Thyroid Cancer: A Retrospective Study on a Korean Population

BACKGRUOUND

There is debate about ultrasonography screening for thyroid cancer and its cost-effectiveness. This study aimed to evaluate the cost-effectiveness of early screening (ES) versus symptomatic detection (SD) for differentiated thyroid cancer (DTC) in Korea.

METHODS

A Markov decision analysis model was constructed to compare the cost-effectiveness of ES and SD. The model considered direct medical costs, health outcomes, and different diagnostic and treatment pathways. Input data were derived from literature and Korean population studies. Incremental cost-effectiveness ratio (ICER) was calculated. Willingness-to-pay (WTP) threshold was set at USD 100,000 or 20,000 per quality-adjusted life year (QALY) gained. Sensitivity analyses were conducted to address uncertainties of the model's variables.

RESULTS

In a base case scenario with 50 years of follow-up, ES was found to be cost-effective compared to SD, with an ICER of $2,852 per QALY. With WTP set at $100,000, in the case with follow-up less than 10 years, the SD was cost-effective. Sensitivity analysis showed that variables such as lobectomy probability, age, mortality, and utility scores significantly influenced the ICER. Despite variations in costs and other factors, all ICER values remained below the WTP threshold.

CONCLUSION

Findings of this study indicate that ES is a cost-effective strategy for DTC screening in the Korean medical system. Early detection and subsequent lobectomy contribute to the cost-effectiveness of ES, while SD at an advanced stage makes ES more cost-effective. Expected follow-up duration should be considered to determine an optimal strategy for DTC screening.

Comparison of postoperative pain between transoral and conventional thyroidectomy: a propensity score-matched analysis

BACKGROUND

The extent of postoperative pain following transoral thyroidectomy is not well-understood and remains a subject of debate. This study aims to analyze and compare postoperative pain levels between patients undergoing transoral and conventional transcervical thyroidectomy.

METHODS

A prospective evaluation on postoperative pain was conducted in 310 patients undergoing conventional thyroidectomy and 194 undergoing transoral thyroidectomy. Pain levels were evaluated using the numerical rating scale (NRS, ranging from 0 to 10) through preoperative and postoperative questionnaires at specified time points: 1, 3, and 6 days, and 1 and 3 months following surgery. Propensity score-matched analysis was carried out based on six covariates: sex, age, body mass index, extent of thyroidectomy, tumor size, and central neck dissection.

RESULTS

After propensity score matching based on the six covariates, 121 patient pairs were identified from each group. Within this matched cohort, postoperative pain scores significantly worsened 1 day after surgery but showed progressive recovery up to 3 months post-surgery in both groups. The transoral group exhibited higher postoperative pain scores than the conventional group from day 1 (4.43 ± 2.6 vs. 3.11 ± 2.5, p < 0.001) to day 6 (1.76 ± 1.9 vs. 1.13 ± 1.6, p = 0.016) post-surgery, with no significant difference noted at 1 month. Among transoral procedures, pain scores were significantly higher for the endoscopic approach compared to the robotic approach on days 1 (5.52 ± 2.3 vs. 4.29 ± 2.3, p = 0.028) and 3 (3.52 ± 2.5 vs. 2.64 ± 2.0, p = 0.047) post-surgery.

CONCLUSIONS

Postoperative pain was significantly higher in transoral thyroidectomy compared to conventional thyroidectomy up to 6 days post-surgery. Within the transoral group, the robotic procedure resulted in lower pain levels than the endoscopic approach during the early postoperative period.

Long-Term Changes in the Mortality Rates of Thyroid Cancer in Korea: Analysis of Korean National Data from 1985 to 2020

BACKGRUOUND

Thyroid cancer mortality has been largely overlooked as relatively stable given the large gap between thyroid cancer incidence and mortality. This study evaluated long-term trends in age-standardized mortality rates (ASMRs) throughout Korea and compared them with mortality data reported by the Surveillance, Epidemiology, and End Results (SEER).

METHODS

Cancer-specific mortality data from 1985 to 2020 were obtained from Statistics Korea. ASMRs from thyroid cancer were calculated based on the Korean mid-year resident registration population of 2005. We assessed SEER*Explorer and downloaded the mortality data.

RESULTS

The ASMR increased from 0.19 to 0.77/100,000 between 1985 and 2002 but decreased continuously to 0.36/100,000 in 2020. The annual percent change (APC) in the ASMR between 1985 and 2003 and between 2003 and 2020 was 6.204 and -4.218, respectively, with similar patterns observed in both men and women. The ASMR of the SEER showed a modest increase from 1988 to 2016 and then stabilized. In subgroup analysis, the ASMR of the old age group (≥55 years) increased significantly from 0.82 in 1985 to 3.92/100,000 in 2002 (APC 6.917) but then decreased again to 1.86/100,000 in 2020 (APC -4.136). ASMRs according to the age group in the SEER showed a relatively stable trend even in the elderly group.

CONCLUSION

The ASMR of thyroid cancer in Korea had increased from 1985 to 2002 but has since been steadily decreasing. This trend was mainly attributed to elderly people aged 55 or over. The absolute APC value of Korea was much higher than that of the SEER.

Cost-Effectiveness of Active Surveillance Compared to Early Surgery of Small Papillary Thyroid Cancer: A Retrospective Study on a Korean Population

BACKGROUND

Recently, active surveillance (AS) has been introduced as an alternative to early surgery (ES) for the management of papillary thyroid microcarcinoma (PTMC), because of its indolent features and low mortality. However, its cost effects have not been determined and the findings of current studies differ, according to each country's medical system.

METHODS

A Markov model was constructed to compare the cost-effectiveness of AS and ES, based on a reference case of a 40-year-old patient diagnosed with PTMC. Costs and transition probabilities were derived from previous clinical studies in Korean populations, and the incremental cost-effectiveness ratio (ICER) and net monetary benefit (NMB) were calculated. The willingness-to-pay (WTP) threshold was set at USD 100,000 per quality-adjusted life year (QALY) gained. Sensitivity analyses were conducted to address the uncertainties in the model's variables.

RESULTS

From the base scenario, the cumulative costs and effectiveness were both higher in ES than AS. The ICER for ES, compared with AS, was USD 6,619.86/QALY, lower than the set WTP. The NMB difference between AS and ES increased across the stages (USD 5,980 at the first stage and USD 159,667 at the last stage). The ICER increased along with decreasing age and increasing cost of surgery. The higher the ES utility score and the lower that of AS, the more cost-effective ES, with WTP set at USD 30,000.

CONCLUSION

In the current Korean medical system, ES is more cost-effective than AS. ES is more cost-effective as it is diagnosed at young age and followed-up for a long time.

Survival Comparison of Incidentally Found versus Clinically Detected Thyroid Cancers: An Analysis of a Nationwide Cohort Study

BACKGRUOUND

The true benefit of thyroid cancer screening is incompletely understood. This study investigated the impact of ultrasound screening on thyroid cancer outcomes through a comparison with symptomatic thyroid cancer using data from a nationwide cohort study in Korea.

METHODS

Cox regression analysis was performed to assess the hazard ratios (HRs) for all-cause and thyroid cancer-specific mortality. Considering the possible bias arising from age, sex, year of thyroid cancer registration, and confounding factors for mortality (including smoking/drinking status, diabetes, and hypertension), all analyses were conducted with stabilized inverse probability of treatment weighting (IPTW) according to the route of detection.

RESULTS

Of 5,796 patients with thyroid cancer, 4,145 were included and 1,651 were excluded due to insufficient data. In comparison with the screening group, the clinical suspicion group was associated with large tumors (17.2±14.6 mm vs. 10.4±7.9 mm), advanced T stage (3-4) (odds ratio [OR], 1.24; 95% confidence interval [CI], 1.09 to 1.41), extrathyroidal extension (OR, 1.16; 95% CI, 1.02 to 1.32), and advanced stage (III-IV) (OR, 1.16; 95% CI, 1.00 to 1.35). In IPTW-adjusted Cox regression analysis, the clinical suspicion group had significantly higher risks of all-cause mortality (HR, 1.43; 95% CI, 1.14 to 1.80) and thyroid cancer-specific mortality (HR, 3.07; 95% CI, 1.77 to 5.29). Mediation analysis showed that the presence of thyroid-specific symptoms was directly associated with a higher risk of cancer-specific mortality. Thyroid-specific symptoms also indirectly affected thyroid cancer-specific mortality, mediated by tumor size and advanced clinicopathologic status.

CONCLUSION

Our findings provide important evidence for the survival benefit of early detection of thyroid cancer compared to symptomatic thyroid cancer.

Cancer and Mortality Risks of Graves' Disease in South Korea Based on National Data from 2010 to 2019

Purpose

This study aimed to investigate Graves' disease (GD) associated cancer and mortality risk using a Korean population-based study.

Patients and Methods

We included 6435 patients with GD using the Korean National Health Insurance Service-National Sample Cohort database from 2010 to 2019. Data concerning such patients were compared in a 1:5 ratio with age- and sex-matched non-GD group (n=32,175). Eighteen subdivided types of cancer and cancers-in-total were analyzed. In addition to the mortality analysis, subgroup analyses were performed according to age and sex.

Results

After adjustment, the hazard ratio (HR) of the GD group for cancer-in-total was 1.07 (95% confidence interval [CI], 0.91-1.27), showing no difference when compared to the non-GD group. However, among different types of cancer, the thyroid cancer risk of the GD group was higher than that of the non-GD group (HR=1.70; 95% CI, 1.20-2.39). When subdivided by age and sex, the thyroid cancer risk of the GD group in males aged 20-39 years was higher than that of the non-GD group (HR=7.00; 95% CI, 1.48-33.12). The mortality risk of the GD group was not different from that of the non-GD group (HR=0.86; 95% CI, 0.70-1.05).

Conclusion

In South Korea, patients with GD had a higher risk of thyroid cancer than the non-GD group. In particular, males aged 20-39 years with GD were more likely to have thyroid cancer than the non-GD group.