Thyroid cancer in Fukushima children increased 20-fold

Latest results of the Fukushima thyroid screenings confirm worrying trend

In 2011, people in Japan were exposed to radioactive fallout. Some still live in contaminated regions where they are exposed to elevated levels of radiation on a daily basis: radioactive hot-spots on the side of the road, in rice paddies or in sandboxes, contaminated mushrooms or algae, contaminated groundwater, and recontamination from forest fires or flooding.

One of the most dreaded effects of radioactive exposure is the development of cancer through mutation of the DNA. Thyroid cancer in children is certainly not the most dangerous form of radiation-induced cancer, but it is probably the easiest to detect. For one thing, the latency periods before a cancer develops are relatively short, while at the same time, thyroid cancer in children is an extremely rare disease, so that even a slight absolute increase can be statistically detected. Accordingly, in 2011, there was great pressure on Japanese authorities to investigate the development of thyroid cancer in children and adolescents in Fukushima by conducting long-term screening examinations.

For almost 10 years now, Fukushima Medical University has been regularly examining the thyroid glands of people who lived in Fukushima Prefecture at the time of the meltdowns and were under 18 years of age. Initially, this group consisted of about 368,000 individuals. Of these, 300,000 (about 82%) were successfully screened in the first few years. After the initial screening (2011-2014), follow-up examinations of these children took place every two years. The second examination has already been completed, the third examination is in its final stage, the fourth series of examinations has been running since 2018, and the fifth since 2020.

In the initial investigation in Fukushima, 116 abnormal biopsies were found. Amongst these, 101 cases of cancers were found that were so aggressive that they required surgery. The patients with abnormal biopsies were 6 to 18 years old (average of 14.9 years) at the time of the nuclear disaster. This unexpectedly high number was explained by Fukushima Medical University as a screening effect, the phenomenon of identifying more cases of disease in large-scale screening than would be expected. While the exact magnitude of this screening effect in the first round is unknown, it can be ruled out that the increased cancer rates in subsequent screenings are consequences of a screening effect, because all of these children had already been examined and found to be cancer-free in previous screenings. They must therefore have developed the cancer between the screening examinations.

In the 2nd screening round, 54 cancer cases were found in 71 abnormal biopsies (age at the time of the nuclear disaster 5-18, average of 12.6 years), in the 3rd screening round, another 27 cases were found in 31 abnormal biopsies (age at the time of the nuclear disaster 5-16, average of 9.6 years), and in the current 4th round, 16 new diagnoses have been made in 27 abnormal biopsies (age at the time of the nuclear disaster 0-12, average of 8.0 years). A total of 46 children with suspicious fine-needle biopsies are still under observation and have not yet undergone surgery. The steadily decreasing average age in the screenings is striking: with time, more and more cancer cases are becoming apparent in patients who were still very young at the time of the nuclear disaster, even under 5 years of age.

Incidentally, adolescents in the study cohort who turn 25 are excluded from the main study and transferred to a newly created cohort, the „Age 25 Milestone“ group. In this group, 4 additional cases of thyroid cancer have been registered, with 7 conspicuous biopsies so far. The number of unreported cases is likely to be much higher: the participation rate in this study is just 8%. The creation of a new study cohort is generally seen as a measure by FMU to further reduce the number of diagnosed cancer cases.

In addition, there are 11 thyroid cancer cases diagnosed in children from the study cohort, but not during the official screenings. These patients were seen and diagnosed at Fukushima University Hospital. These 11 cases are not reported in the official results, although they show identical tumor entities and occurred in patients who are in the actual study cohort. The 11 cases came to light in June 2017. How many more cases have been diagnosed but not reported since then is unknown. In addition, data from other hospitals in Japan are not available, and patients from contaminated areas outside Fukushima Prefecture are not examined at all, so the unreported number of thyroid cancer cases among patients who were children in the contaminated areas at the time of the meltdowns is likely to be much higher. Nevertheless, the total number of thyroid cancer cases in Fukushima currently stands at 213 (198 official cases from the serial examinations, 4 cases from the Age 25 Milestone cohort and 11 cases from the Fukushima University Hospital).

It is interesting to compare these figures with the overall Japanese incidence rate. The official incidence rate of thyroid cancer in children under 25 in Japan is about 0.59 per 100,000 per year, which means that in the cohort of about 218,000 children, about 1.3 new thyroid cancer cases per year would be expected. Today, 10 years after the beginning of the nuclear disaster, just under 13 thyroid cancer cases would thus have been expected in the study population.

However, the actual number of thyroid cancer cases in Fukushima of 213 is higher by a factor of 16. If we consider only the 112 cases diagnosed after the initial screening and thus not suspected to be caused by a screening effect of any kind, the number of confirmed cases is 20 times higher than the number of expected thyroid cancer cases (5.5 new cases after the end of the initial 1st screening in 2014).

In the following graph, the officially confirmed thyroid cancer cases (in blue) are compared to the cases expected mathematically in the screening cohort (in orange). It can be seen that the number of cases increased steadily over the course of the initial screening, and continue to increase beyond that, in the years 2014-2020 – an effect that cannot be explained by any kind of screening effect.



In addition, the geographic distribution of thyroid cancer rates corresponds to the level of radioactive contamination. A significantly higher incidence of thyroid cancer in children was recorded in the 13 most severely contaminated municipalities in eastern Fukushima than in the less contaminated areas in the north, south and central parts of the prefecture. The incidence was lowest in the western part of the prefecture, where the radioactive fallout was also least pronounced.




The declining number of expected thyroid cancer cases between 2016-2021 is attributable to declining screening participation rates. Since these people's cancers would no longer show up in screenings, the number of expected cancer cases also declines. While, out of a total pediatric population of little more than 380.000, about 300,000 children were examined in the initial screening from 2011-2014, that number dropped by 10% to about 270,000 in the second screening from 2014-2016 and by another 10% in the third screening from 2016-2018 to just under 218,000. To date, only about 181,000 children have been screened in the fourth screening, and only 41 have been screened so far in the fifth screening. In relative terms, the percentage of children screened in Fukushima has dropped from an initial 82% in the 1st screening to 71% in the 2nd screening, 65% in the 3rd screening, and currently to 62% in the ongoing 4th screening.



There seems to be a system behind this trend: Fukushima Medical University, which is in charge of the study, has been sending staff to schools in the prefecture for years to educate children about their "right not to participate" and the "right not to know". On the study forms, there is now a prominent "opt-out" option for people who wish to be removed from the screening. FMU seems to encourage people to opt out of the study. The drop in participation can also be explained by the removal of people over 25 years from the main study. Are FMU staff concerned that the disturbing trend of increasing numbers of thyroid cancer cases will continue? Are they uncomfortable with data that contradicts the thesis, propagated since the beginning of the nuclear disaster, that the multiple meltdowns would not lead to additional cancers?

In addition to thyroid cancer, other types of malignancies and other diseases triggered or adversely affected by ionized radiation are expected to increase. The FMU thyroid studies represent the only scientific study that can provide any relevant information at all about the health consequences of the Fukushima nuclear disaster. And they are currently in danger of being undermined by the proponents of nuclear energy such as IAEA, which has entered a cooperation with FMU and by the Japanese government, which is trying to dispel any concerns about the meltdowns and nuclear energy as a whole.

The people of Japan have an inalienable right to health and to life in a healthy environment. The examination of children's thyroid glands benefits not only the patients themselves, whose cancers can be detected and treated at an early stage, but also the entire population, which is affected by irradiation from radioactive fallout. The correct continuation and scientific monitoring of thyroid examinations are therefore in the public interest and must not be thwarted by political or economic motives. It is important to continue to critically accompany these developments from the outside.

Dr. med. Alex Rosen
Pediatrician and Co-Chair of the German affiliate of IPPNW


Note: this article was first published in IPPNW Germany's member magazine ippnw forum in 03/21