Thyroid Cancer Screening: Fukushimaís Experience

Tomoko INAMASU, International Agency for Research on Cancer, France

1 Section of Environment and Radiation, International Agency for Research on Cancer, Lyon, France

Purpose: Thyroid cancer screening does not reduce mortality, and its legitimacy has been questioned in countries with extensive implementation of increased diagnostic surveillance programmes. The thyroid ultrasound examination programme started after the radiation emergency in Fukushima in 2011 detected 152 suspected/confirmed malignant cases in 300,476 children (ages 0-18) screened by the end of 2015. This result is often interpreted as an effect of radiation exposure, rather than of the mass screening. We aimed to address impact of the thyroid screening in Fukushima on thyroid cancer incidence, prevalence, as well as potential for over-diagnosis/overtreatment.
Methods: We reviewed relevant scientific papers, government reports, newspaper and popular magazine articles published in Japanese or English between March 2011 and December 2015.
Results: Legitimacy of thyroid screening in Fukushima has been questioned in scientific papers in English since early stages, while rarely discussed in Japanese. Little has been published on thyroid cancer incidence and mortality in general Japanese population before the accident, potential effects of cancer screening, including thyroid cancer over-diagnosis/overtreatment. Comparisons between thyroid cancer screening after Fukushima and Chernobyl seldom addressed differences in survey methodologies, diagnostic criteria and radiation exposure conditions.
Conclusions: Lack of discussion on impact of the thyroid screening may have created and reinforced unnecessary anxiety among the affected population in Fukushima. Some of the discourses in Japanese mass media were not built on scientific evidence, but likely to be more influential information source for the general population. Enhanced information provision in the Japanese language may help affected people start discuss necessity of thyroid screening and make informed decisions.
Funding source: This work was undertaken during the tenure of a Postdoctoral Fellowship from the International Agency for Research on Cancer, partially supported by the European Commission FP7 Marie Curie Actions - People - Co-funding of regional, national and international programmes (COFUND).