Exposure of the thyroid gland to ionizing radiation at a young age is the main recognized risk factor for differentiated thyroid cancer. After the Chernobyl and Fukushima nuclear accidents, thyroid cancer screening was implemented mainly for children, leading to case over-diagnosis as seen in South Korea after the implementation of opportunistic screening (where subjects are recruited at healthcare sites). The aim of cancer screening is to reduce morbidity and mortality, but screening can also cause negative effects on health (with unnecessary treatment if over-diagnosis) and on quality of life.

This paper from the SHAMISEN special issue (Nuclear Emergency Situations - Improvement of Medical And Health Surveillance) presents the principles of cancer screening, the lessons learned from thyroid cancer screening, as well as the knowledge on thyroid cancer incidence after exposure to iodine-131.

The SHAMISEN Consortium recommends to envisage systematic health screening after a nuclear accident, only when appropriately justified, i.e. ensuring that screening will do more good than harm. Based on the experience of the Fukushima screening, the consortium does not recommend mass or population-based thyroid cancer screening, as the negative psychological and physical effects are likely to outweigh any possible benefit in affected populations; thyroid health monitoring should however be made available to persons who request it (regardless of whether they are at increased risk or not), accompanied with appropriate information and support.

甲状腺年轻时接受电离辐射是公认的分化型甲状腺癌的主要危险因素。在切尔诺贝利核电站和福岛核事故发生后，主要针对儿童实施甲状腺癌筛查，导致机会性诊断过度，如在韩国进行机会性筛查后（在医疗机构招募受试者）。癌症筛查的目的是降低发病率和死亡率，但是筛查也会对健康（如果过度诊断会导致不必要的治疗）和生活质量造成负面影响。

本文来自SHAMISEN特刊（《核紧急情况-改善医疗和健康监测》），介绍了癌症筛查的原理，从甲状腺癌筛查中汲取的经验教训以及暴露于碘131后甲状腺癌发病率的知识。

SHAMISEN财团建议仅在适当理由下，设想核事故后进行系统的健康检查，即确保检查有益无害。根据福岛县筛查的经验，该财团不建议进行大规模或以人群为基础的甲状腺癌筛查，因为负面的心理和生理影响可能超过对受影响人群的任何好处；但是，应向有此要求的人提供甲状腺健康监测（无论他们是否处于增加的风险中），并提供适当的信息和支持。