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Fukushima teens thyroid cancers from overdiagnosis, ‘unlikely’ to be from radiation exposure!!!

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Results of mass screening of children, teens for thyroid cancer following Fukushima nuclear accident
November 29, 2018
Bottom Line: The accident at Japan’s Fukushima Daiichi nuclear power station in 2011 raised grave concerns about radioactive material released into the environment, including concerns over radiation-induced thyroid cancer. Ultrasound screenings for thyroid cancer were subsequently conducted in the Fukushima Health Management Survey. This observational study group includes about 324,000 people 18 or younger at the time of the accident and it reports on two rounds of ultrasound screening during the first five years after the accident. Thyroid cancer or suspected cancer was identified in 187 individuals within five years (116 people in the first round among nearly 300,000 people screened and 71 in the second round among 271,000 screened). The overwhelmingly common diagnosis in surgical cases was papillary thyroid cancer (149 of 152 or 98 percent).
 
US screening data from Fukushima shed light on thyroid cancer in kids
November 29, 2018 — The latest results of mass ultrasound screening of children for thyroid cancer after the Fukushima disaster were published online on November 29 by JAMA Otolaryngology — Head & Neck Surgery. The study provides vital data on thyroid cancer and may lead to growing demands outside of Japan for more ultrasound scans in younger people, increasing the risk of overdiagnosis, experts have warned.
In an observational study, Dr. Akira Ohtsuru, PhD, from the department of radiation health management at Fukushima Medical University, and colleagues analyzed the incidence of thyroid cancer in children and adolescents screened with two rounds of ultrasound within five years of the 2011 disaster at the Fukushima Daiichi nuclear power station. The main question they addressed was, what is the pattern by age group of cancer detection via ultrasound screening of the thyroid among children and young adults?
The first round of ultrasound screening was carried out between 2011 and 2013, and the second round between 2014 and 2015. A total of 324,301 individuals younger than 18 years at the time of the disaster were included in the analysis.
Thyroid cancer, or suspected cancer, was identified in 187 patients within five years (116 people in the first round among nearly 300,000 people screened and 71 in the second round among 271,000 screened). By far the most common diagnosis in surgical cases was papillary thyroid cancer (149 of 152, or 98%). Overall, the distribution pattern of the incidence rate by age group in second-round examinations increased with age, according to Ohtsuru and colleagues.
Looming risk of overdiagnosis
Large-scale ultrasound screening can identify many detectable cancers from a sizable pool of nonclinical and subclinical thyroid cancers among individuals of a relatively young age, in an age-dependent manner. However, to avoid overdiagnosis, an improvement in screening strategy based on the understanding of the natural history of thyroid cancer will be urgently needed, Ohtsuru and colleagues explained.
“The fundamental ethical principle of doing more good than harm should be central to accident management, including conducting thyroid screening that is designed to avoid the problems of potential overdiagnosis,” the researchers wrote. “We should not be influenced by the negative experiences or psychosocial issues of the examinees under the potential for overdiagnosis.”
Because the natural progression of thyroid cancer in young patients remains unknown, further studies are required, they believe. Data from the Fukushima Health Management Survey may contribute to understanding how to conduct future screening programs to both limit overdiagnosis and support an accurate evaluation of the effect of low-dose radiation on the thyroid glands of children and adolescents, they stated.
The 2011 disaster raised grave concerns about radioactive material released into the environment, including over radiation-induced thyroid cancer. Ultrasound screenings for thyroid cancer were subsequently conducted in the Fukushima Health Management Survey. The debate over whether a rise in thyroid cancer among children in Japan is related to the nuclear disaster — or whether it’s simply due to overdiagnosis as children near the site of the disaster are screened for the disease — has been ongoing since 2015.
Reaction to latest results
In a linked commentary also published in JAMA Otolaryngology — Head & Neck Surgery, U.S. experts welcomed the research.
“Before the Fukushima Survey, we did not know if there was a substantial reservoir of subclinical thyroid cancer in children and adolescents. These data show that there is a very large reservoir,” wrote Dr. Andrew J. Bauer, from the Pediatric Thyroid Center at Children’s Hospital of Philadelphia Division of Endocrinology and Diabetes, and Dr. Louise Davies, from the VA Outcomes Group at the Department of Veterans Affairs Medical Center in White River Junction, VT.
More children and adolescents are likely to undergo ultrasound of the thyroid in the U.S., leading to the detection of a substantial reservoir of subclinical thyroid cancer. This could open up children to the risks and consequences of overdiagnosis and subsequent treatment that may worsen health, as has happened within a segment of the adult population, Bauer and Davies continued.
“We are still left with the difficult question of how to apply the concepts of overdiagnosis in this scenario. Pediatric thyroid cancer has a 98% rate of survival, even for patients with pulmonary metastasis, so benefits of treatment should not be considered in regard to effects on disease-specific mortality,” they pointed out.
Ohtsuru gave a lecture on this topic at the 5th International Expert Symposium in Fukushima on Radiation and Health, entitled “Chernobyl+30, Fukushima+5: Lessons and Solutions for Fukushima’s Thyroid Question.” His full presentation can be downloaded here.
 
Association between screening-detected thyroid cancers, radiation exposure ‘unlikely’ in Fukushima children
November 29, 2018
Many thyroid cancers detected by ultrasound screening in Japanese children in the 5 years after the 2011 Fukushima Daiichi nuclear accident mirror many low-risk, sporadic cases of adult thyroid cancer and are most likely not associated with radiation exposure, according to findings published in JAMA Otolaryngology Head & Neck Surgery.
“Large-scale mass screening of young people using ultrasonography resulted in the diagnosis of a number of thyroid cancers, including potential overdiagnosis cases,” Akira Ohtsuru, MD, PhD, professor in the department of radiation health management at Fukushima Medical University, Japan, told Endocrine Today. “These findings indicate that ultrasonography screening can identify many detectable cancers from large pool of nonclinical and subclinical thyroid cancers among individuals of a relatively young age, in an age-dependent manner.”
The level of radiation exposure in Fukushima immediately after the great earthquake in eastern Japan on March 11, 2011, has been deemed to be much lower than the levels reported in Chernobyl immediately after the 1986 nuclear power station accident, Ohtsuru and colleagues wrote in the study background. However, the researchers noted that there was a divergence in estimations of the thyroid equivalent dose of radiation during the early phase after the accident, as there was little direct measurement of the individuals, whereas radiation-induced thyroid cancers have been rated as causing some of the greatest concern after the accident.
“Thus, health surveillance, including thyroid screening, has been thought to be necessary for both scientific and social reasons,” the researchers wrote.
In an observational study, Ohtsuru and colleagues analyzed data from 324,301 Fukushima residents aged 18 years or younger at the time of the nuclear accident. Researchers assessed the number of detected cases of thyroid cancer during first (fiscal years 2011-2013) and second (fiscal years 2014-2015) rounds of screening, with age groups stratified by 3-year intervals. Researchers compared results against an age-specific incidence of unscreened cancers form a national cancer registry.
Researchers found that, among 299,905 participants screened in the first round (50.5% boys and men; mean age at screening, 15 years), 116 were diagnosed with malignant or suspected thyroid cancer. Among 271,083 participants screened in the second round, (50.4% boys and men; mean age at screening, 13 years), 71 were diagnosed with malignant or suspected thyroid cancer, according to researchers. In both the first- and second-round examinations, mean age at diagnosis was 17 years; however, mean tumor diameter was larger in the first- vs. the second-round screenings (mean, 12.7 mm vs. 9.7).
Papillary thyroid cancer was the most common pathologic diagnosis, they wrote, at 149 of 152 cases (98%). The researchers also noted that the distribution pattern by age group at the time of the accident increased with older age in both screening rounds, with an interval between screenings of about 2.1 years. The number of detected thyroid cancer cases per 100,000 persons was estimated to be approximately 175 for those aged 18 years at the time of the accident in the first round of screening and 97 for those aged 18 years at the time of the accident during the second round of screening.
Researchers calculated that the estimated age-conditional incidence rate of cases per 100,000 person-years was 0.5 for those aged 15 to 17 years, 1 for those aged 18 to 20 years and 1.7 for those aged 21 to 22 years.
“Although a longer observation period is needed, this pattern by age at the time of the accident differs from that of the Chernobyl nuclear power station accident; for example, there was a higher frequency of cases of cancer at younger ages with a relatively short latent period after the Chernobyl nuclear power station accident,” the researchers wrote. “Thus, an association between the large number of thyroid cancers detected and radiation exposure is thought to be very unlikely, in addition to the very low doses of radiation in the Fukushima nuclear power station accident.”
Ohtsuru added that, to ensure the merit of early detection and prevent overdiagnosis via large-scale screening, development of a careful monitoring system is urgently needed based on the understanding of the natural history of thyroid cancer.
In commentary accompanying the study, Andrew J. Bauer, MD, medical director of the Pediatric Thyroid Center at Children’s Hospital of Philadelphia, and Louise Davies, MD, MS, research fellowship director of the VA Outcomes Group at the Veterans Affairs Medical Center in White River Junction, Vermont, wrote that researchers should not assume that every asymptomatically discovered case of pediatric thyroid cancer is a “triumph of early detection.”
“Going forward, research to better define which pediatric thyroid cancers are likely to progress, and a better understanding of the trajectory of the natural history of thyroid cancers detected in early life, is urgently needed,” Bauer and Davies wrote. “The extremely high prevalence of subclinical thyroid cancer shown by the Fukushima Survey, including many with lymph node metastases, suggests that we have much to learn about the natural history of lymph node metastases, but that we should not assume that every asymptomatically identified case of pediatric thyroid cancer is an instance of overdiagnosis.” – by Regina Schaffer
For more information:
Akira Ohtsuru, MD, PhD, can be reached at Fukushima Medical University, Department of Radiation Health Management, 1 Hikarigaoka, Fukushima 960-1295, Japan; email: ohtsuru@fmu.ac.jp.
Disclosures: One of the authors reports he received grants from commercial sponsor JCR Pharmaceuticals Co. Bauer and Davies report receiving travel funds from the International Agency for Research on Cancer.
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December 7, 2018 - Posted by | Fukushima 2018 | ,

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