Incidence and Prognosis of Thyroid Cancer in Children: Based on the SEER Database

Background: Studying the incidence trend and prognosis factors of childhood Thyroid cancer (TC) may better reflect the prevalence of this disease. Objectives: To explore the trends in the incidence of childhood thyroid cancer and the prognosis.Material and Methods: Join-point regression model was used to analyze incidence trend of TC. Cox regression model was applied to explore the survival situation and prognostic factors.Results: The incidence rate of childhood TC increased between 1975 and 2016 from 3.8/million (95%CI: 2.6-5.5) to 11.5/million (95%CI: 9.2-14.1), AAPC = 2.38 (95%CI: 1.98-9.65)) and could be divided into two stages of increasing trends. The incidence rate of Trend1 (1975-2005) increased slowly but Trend2 (2005-2016) increased dramatically. And annual rates of small size tumor (<4cm) and local stage TC in children increased significantly. The overall cumulative survival rate for childhood TC was high up to 97%-99%. Males, the black people, MTC type, distant metastasis, tumor size >= 4 cm, non-primary cancer were the independent risk factors of prognosis of childhood TC.Conclusions and Significance: A contribution of over detection to rising pediatric TC rates might not be able to rule out. Over-treatment to small size and local stage TC in children should be avoided.

Trends in Childhood Thyroid Cancer incidence in Korea and Its Potential Risk Factors

BackgroundAlthough the incidence of thyroid cancer had been increasing until a few years ago, a decrease has been observed in the last years, probably due to the reduction of the screening tests in Korea. Childhood thyroid cancer has been increasing in the past with the same trend as in adults, but there have been few reports on recent trends. We analyzed the trends of thyroid cancer in Korean children and related factors.MethodsFrom national statistics and cancer register database, the data of age-specific incidence rate in Korean childhood thyroid cancer from 1999 to 2017 was obtained, and levels of seaweed intake, the number of computed tomography (CT) and neck ultrasonography (US), obesity prevalence rate, and smoking and alcohol consumption rates in children were analyzed.ResultsThe age-specific incidence of thyroid cancer in Korean children has increased in both genders between 1999 and 2017 (2.0 in 1999 vs. 7.2 in 2017, per population of 100,000), especially in the age group of 14-18 years (1.5 in 1999 vs. 5.5 in 2017, per population of 100,000). During the same period, levels of seaweed intake, number of CT scans and neck US, and prevalence of obesity in children increased significantly, while childhood smoking and alcohol consumption rates decreased.ConclusionUnlike the adult thyroid cancer in Korea, childhood thyroid cancer continues to increase, and the cause might be accompanied by actual increases due to the environmental factors such as excessive iodine intake, exposure to medical radiation, and increased obesity prevalence as well as the screening effect.

Risk perception of the pre-distribution of stable iodine to guardians of children living around the Genkai Nuclear Power Plant, Saga Prefecture, Japan

Iodine thyroid blocking (ITB) is effective for preventing childhood thyroid cancer when radioactive iodine is released into the environment during a nuclear power plant accident. Japan employs the pre-distribution of stable iodine (PDSI) to residents living near nuclear power plants; however, the number of residents who have actually received stable iodine to date remains limited. The aim of this study was to evaluate the profile of guardians of children living around the Genkai Nuclear Power Plant (GNPP) in Japan. We distributed self-administered questionnaires regarding perception of risks associated with administration of stable iodide to approximated 400 guardians of children aged 0–6 in 10 kindergartens located in four municipalities. We obtained responses from 286 guardians, and after excluding invalid responses, 247 were included in the analysis. Logistic regression analysis revealed that living within 5 km of the GNPP (odds ratio [OR] = 4.48, 95% confidence interval [CI]: 2.43–8.24), awareness of preferential implementation of ITB to children (OR = 3.33, 95%CI: 1.78–6.22), and awareness of the prophylaxis booklet published by the local government (OR = 2.53, 95%CI: 1.37–4.68) were independently associated with PDSI for children. The main reasons for not receiving PDSI were “anxiety about the side effects of stable iodine” (40.2%), “distrust of the effectiveness of SI” (23.5%), “complicated procedures for receiving stable iodine” (15.7%) and “missed the date for receiving stable iodine” (8.8%). In the case of ITB implementation during a nuclear emergency, it is necessary to clarify the risk perceptions of guardians and adapt risk communication accordingly.

Change of Age Distribution of Childhood and Adolescent Thyroid Cancer after the Fukushima Nuclear Accident Compared with the Chernobyl Cases

Background and Methods: Comparison of age patterns of childhood and adolescent childhood thyroid cancer after the nuclear accidents in Fukushima and Chernobyl is often used as a criterion of radiationinduced thyroid cancer in Fukushima. The Fukushima Health Management Survey reports that thyroid cancers in Fukushima are unlikely to be radiation-induced, and one reason for the conclusion was no case was found in the age of 0-5 years at exposure. Published data on the health effects of the Chernobyl accident were analysed to assess whether there was one age pattern common in Chernobyl to be used as a criterion of radiation-induced thyroid cancer. Various age distributions of thyroid cancer as to the age at exposure and age at diagnosis, which depend on the country and the extent of radiation contamination, were studied as a function of years after exposure. Results and Conclusion: The highest incidence of thyroid cancer for infants aged 0-4 at exposure was observed only in Belarus. The high incidence of age group 0-4 AE became apparent only after 12 years from the accident in Ukraine and Russia. Age distribution of diagnosed or suspected thyroid cancer cases in Fukushima by age at exposure shifts to younger age side, average age from 14.9 to 8.3 years in 9 years after the accident. This trend agrees with the one in Ukraine and Russia. Because there is no common age pattern in Chernobyl, we should better not use age pattern as a simple criterion of radiation-induced thyroid cancer.

Absorbed radiation doses in the thyroid as estimated by UNSCEAR and subsequent risk of childhood thyroid cancer following the Great East Japan Earthquake

The identification of thyroid cancers among children after the Chernobyl nuclear power plant accident propelled concerns regarding long-term radiation effects on thyroid cancer in children affected by the Fukushima Daiichi nuclear power plant accident in Fukushima, Japan. Herein we consider the potential association between absorbed dose in the thyroid and the risk of developing thyroid cancer as detected by ultrasonography on 300 473 children and adolescents aged 0–18 years in Fukushima. The absorbed dose mentioned in the present study indicates the sum of that from external exposure and that from internally deposited radionuclides. We grouped participants according to estimated absorbed doses in each of 59 municipalities in Fukushima Prefecture, based on The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2013 report. The 59 municipalities were assigned to quartiles by dose. We limited our analyses to participants aged ≥6 years because only one case of thyroid cancer was observed in participants aged ≤5 years; 164 299 participants were included in the final analysis. Compared with the lowest dose quartile, the age- and sex-adjusted rate ratios (95% confidence intervals) for the low-middle, high-middle and highest quartiles were 2.00 (0.84–4.80), 1.34 (0.50–3.59) and 1.42 (0.55–3.67) for the 6–14-year-old groups and 1.99 (0.70–5.70), 0.54 (0.13–2.31) and 0.51 (0.12–2.15) for the &gt;15-year-old group, respectively. No dose-dependent pattern emerged from the geographical distribution of absorbed doses by municipality, as estimated by UNSCEAR, and the detection of thyroid cancer among participants within 4–6 years after the accident. Ongoing surveillance might further clarify the effects of low-dose radiation exposure on thyroid cancer in Fukushima.

Area Dose Response of Prevalent Childhood Thyroid Cancers after the Fukushima Nuclear Power Plant Accident

Background and Methods: After the Fukushima Nuclear Power Plant accident, thyroid ultrasound screening was carried out on all residents of ages≤18 years at the accident. In order to find the cause for thyroid cancer prevalence, area dose dependence of childhood thyroid cancer proportion in the first and second round screening (E-I, E-II), and in 6 years as a whole (E-I+II) was analyzed for external dose estimated by Fukushima Health Management Survey and effective dose estimated by UNSCEAR. The results were analyzed by the regression analysis of Microsoft Excel. Results: Thyroid cancer incidence within 4-6 years and prevalence in 6 years after the accident had tendency to increase with doses. In OM-model according to Ohira’s map, thyroid cancer prevalence in E-I+II after 6 years showed linear prevalence-effective dose response with positive coefficient 5.6 (CI=3.4-7.9) (cancer cases / 100,000 / mSv) in the 1.6–5 mSv range. In F-model according to official regional division, thyroid cancer proportion in E-II and E-I+II showed linear response to UNSCEAR effective dose with R2>0.86 and p<0.075. This correlation was higher than the correlation between external dose and effective dose with R2=0.71. Conclusion: The observed linear area dose relation in 6 years after exposure suggests highly probable association between childhood thyroid cancer in Fukushima and radiation exposure. UNSCEAR effective dose was found to give the best fit to linear regression line for E-II and E-I+II, irrespective of models. Linear dose response for reasonable area division can be a direct evidence for radiation related thyroid cancer because linear dose response cannot be observed in mass-screening for sporadic thyroid cancers.