In this blog post, we examine the causes of the sharp increase in thyroid cancer diagnoses and screenings in South Korea, as well as the resulting issues of overtesting and overdiagnosis.
Trends in the Increase of Thyroid Cancer in South Korea
Since the 1990s, the number of thyroid cancer patients in South Korea has risen sharply. According to data from Statistics Korea, the number of thyroid cancer patients, which stood at approximately 4,000 in 1992, increased significantly to about 126,000 in 2008.
Globally, the incidence of thyroid cancer is also on the rise. Some scholars attribute this to radiation accidents such as those at Chernobyl and Fukushima, as well as an aging population. However, the rate of increase in South Korea is far greater than in other countries. While the increase in developed nations is typically a few-fold, South Korea’s rate is estimated to have risen approximately 11-fold over the past decade, a fact that has drawn significant attention.
Reasons for Concerns About Overtesting and Overdiagnosis
The most frequently cited cause of the sharp rise in thyroid cancer incidence is the increased detection of micro-papillary carcinomas resulting from widespread ultrasound screening. Papillary carcinomas grow slowly and rarely metastasize; very small lesions may never cause any symptoms throughout a person’s lifetime. Since ultrasound can detect even these tiny lesions, it is highly likely that the expansion of screening has led to an increase in the number of patients.
Papillary thyroid cancer is often less than 5 mm in size and is easily detected by ultrasound. Some experts argue that we should reevaluate whether it is appropriate to classify such naturally benign lesions as “cancer.” On the other hand, medical societies maintain that the value of early diagnosis cannot be completely dismissed, as a very small proportion of these lesions may develop into more aggressive forms.
Costs and Healthcare Burden
According to a study by the Korea Institute for Health and Social Affairs, the annual cost of thyroid ultrasound screenings is substantial. With the total cost estimated at hundreds of billions of won, and assuming the cost per screening is approximately 40,000 won, it is clear that a large number of screenings have been conducted. This places a significant burden on both public and private healthcare systems.
Most patients diagnosed with thyroid cancer undergo a thyroidectomy, and even after surgery, initial care and follow-up tests are required. It has been reported that the combined cost of initial post-operative care and follow-up tests over approximately two years amounts to several million won per patient. Multiplying this by the total number of patients results in substantial national healthcare expenditures.
Perspectives on Survival Rates and the Effectiveness of Screening
The 5-year relative survival rate for thyroid cancer is very high. According to statistics, the 5-year relative survival rate already exceeds 95%, and recent reports indicate it is approaching nearly 100%. Such a high survival rate raises questions about whether the expansion of screening has actually significantly reduced mortality rates.
When evaluating the effectiveness of screening, the possibility of bias must be considered. A prime example is lead-time bias: when cancer is detected earlier through screening, it may simply extend the “period of living with the cancer,” giving the appearance that actual survival time has increased. The phenomenon of higher 5-year survival rates among patients detected through screening may be the result of this optical illusion.
Critics point out that actual clinical and epidemiological data provide weak evidence that the expansion of early screening has led to a significant reduction in the total number of deaths from thyroid cancer. Meanwhile, among patients who undergo surgery, some experience complications that interfere with daily life, such as hand tremors or vocal cord paralysis; it has been reported that approximately 10% of surgical patients experience such issues.
Principles of Public Screening and Policy Implications
The principles for national screening programs, as outlined by the World Health Organization (WHO) and others, stipulate that the target disease must be significant, the screening must be cost-effective, and, above all, screening must actually reduce mortality from the disease. Cancer screening programs funded by the national budget must be evaluated to ensure they meet these criteria.
Current thyroid cancer screening and diagnostic practices have been criticized for failing to have a significant impact on reducing mortality rates; rather, they have led to overdiagnosis and unnecessary surgeries, thereby increasing the burden of medical costs on both the state and individuals. Therefore, a cost-effectiveness reassessment and a cautious approach are necessary regarding widespread ultrasound screening of asymptomatic individuals through public funding.
Summary and Recommendations
In summary, the sharp increase in the number of thyroid cancer patients in South Korea is closely related to the increased detection of papillary microcarcinomas resulting from the expansion of ultrasound screening, which raises concerns about over-screening and over-diagnosis. The fact that the clinical course of papillary carcinoma is generally favorable and the 5-year relative survival rate is very high, combined with the potential for time-shortening bias and the significant number of patients suffering from postoperative complications, provides sufficient grounds to reevaluate current screening practices.
To use the national budget efficiently and reduce unnecessary treatments and complications for patients, it is advisable to reevaluate the justification and cost-effectiveness of widespread ultrasound screening of asymptomatic members of the general public, while strengthening the principles of selective screening and treatment for clinically indicated cases, such as those with symptoms or palpable masses.
