Effectiveness of ultrasonographic screening for thyroid cancer: round-table conference in the National Evidence- based Healthcare Collaborating Agency (NECA) in conjunction with the Korean Thyroid Association

Low-Level Environmental Mercury Exposure and Thyroid Cancer Risk Among Residents Living Near National Industrial Complexes in South Korea: A Population-Based Cohort Study

Background: Previous studies suggested that mercury may be linked to thyroid cancer due to its bioaccumulation in the thyroid gland, but no studies have evaluated the association between mercury exposure and thyroid cancer risk. We examined the relationship between mercury exposure and thyroid cancer risk, with the potential modification of hematological parameters. Methods: We performed a secondary analysis of a prospective cohort study among residents living near industrial complexes in South Korea (recruited from 2003 to 2011). Incident thyroid cancer cases (C73, ICD-10 code) were identified from the National Cancer Registry and Statistics Korea. Urinary mercury concentrations were measured using thermal decomposition amalgamation atomic absorption spectrometry (TDA-AAS). Cox proportional hazards regression models (adjusted for age, sex, educational level, smoking status, and employment) were used to estimate the hazard ratio (HR) and confidence interval [CI] between mercury exposure and the incidence of thyroid cancer. Results: We documented 69 cases of thyroid cancer in a total of 5213 participants during follow-up (median 8.7 years). The geometric mean of urinary mercury concentration was 1.8 μg/L for thyroid cancer cases and 1.2 μg/L for noncases (p for difference = 0.001). After adjusting for potential confounders, those in the highest tertile of urinary mercury levels had a twofold higher risk of thyroid cancer (HR = 1.97 [CI 1.03 - 3.80] in the highest tertile vs. the lowest tertile, p for trend = 0.043). This association was stronger for those with lower mean corpuscular volume and mean corpuscular hemoglobin status. Conclusions: Urinary mercury concentration was positively associated with the risk of thyroid cancer among residents living near national industrial complexes, and this association was influenced by red blood cell indices status. These results provide some evidence suggesting the adverse effects of environmental metal pollution in the development of thyroid cancer.

Association among Body Mass Index, Genetic Variants of FTO, and Thyroid Cancer Risk: A Hospital-Based Case-Control Study of the Cancer Screenee Cohort in Korea

Purpose

Obesity has been determined to be associated with fat mass and obesity-associated (FTO) gene and thyroid cancer risk. However, the effect of combined interactions between obesity and the FTO gene on thyroid cancer needs further investigation. This study aimed to examine whether interactions between body mass index (BMI) and the FTO gene are associated with an increased risk of thyroid cancer.

Materials and Methods

A total of 705 thyroid cancer cases and 705 sex- and age-matched normal controls were selected from the Cancer Screenee Cohort in National Cancer Center, Korea. A conditional logistic regression model was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) for the measure of associations and the combined effect of BMI and FTO gene on thyroid cancer.

Results

BMI was associated with an increased risk of thyroid cancer in subclasses of overweight (23–24.9 kg/m²; adjusted OR, 1.50; 95% CI, 1.12 to 2.00) and obese (≥ 25 kg/m²) (adjusted OR, 1.62; 95% CI, 1.23 to 2.14). There were positive associations between the FTO genetic variants rs8047395 and rs8044769 and an increased risk of thyroid cancer. Additionally, the combination of BMI subclasses and FTO gene variants was significantly associated with thyroid cancer risk in the codominant (rs17817288), dominant (rs9937053, rs12149832, rs1861867, and rs7195539), and recessive (rs17817288 and rs8044769) models.

Conclusion

Findings from this study identified the effects of BMI on thyroid cancer risk among individuals carrying rs17817288, rs9937053, rs12149832, rs1861867, rs7195539, and rs8044769, whereas the effects of BMI may be modified according to individual characteristics of other FTO variants.

Public health implications of overscreening for carotid artery stenosis, prediabetes, and thyroid cancer

Background

Overscreening occurs when people without symptoms undergo tests for diseases and the results will not improve their health. In this commentary, we examine three examples of how campaigns to screen and treat specific vascular, metabolic, and oncologic diseases in asymptomatic individuals have produced substantial overdiagnosis and may well have contributed to more harm than good. These conditions were chosen because they may not be as well known as other cases such as screening for breast or prostate cancer.

Main text

Screening for carotid artery stenosis can be a lucrative business using portable equipment and mobile vans. While this fatty buildup of plaque in the arteries of the neck is one risk factor for ischemic stroke, current evidence does not suggest that performing carotid dopplers to screen for CAS reduces the incidence of stroke or provide long-term benefits. After a positive screening, the follow-up procedures can lead to heart attacks, bleeding, strokes, and even death. Similarly, many organizations have launched campaigns for “prediabetes awareness.” Screening for prediabetes with a blood sugar test does not decrease mortality or cardiovascular events. Identifying people with prediabetes could lead to psychological stress and starting medication that may have significant side effects. Finally, palpating people’s necks or examining them with ultrasounds for thyroid cancer is common in many countries but ineffective in reducing mortality. Deadly forms of thyroid cancer are rare, and the overall 5-year survival rate is excellent. Interventions from treatment for more prevalent, less aggressive forms of thyroid cancer can lead to surgical complications, radiation side effects, or require lifelong thyroid replacement therapy.

Conclusions

Screening for carotid artery stenosis, prediabetes, and thyroid cancer in an asymptomatic population can result in unnecessary, harmful, and costly care. Systemic challenges to lowering overscreening include lack of clinician awareness, examination of conflicts of interests, perverse financial incentives, and communication with the general public.