It may sound like a subtle difference between between population thyroid screening and a program of thyroid monitoring, but they’re actually very different.
Prof. Louise Davies: Member of an International Task Force Making Recommendations on Thyroid Cancer Monitoring in the Wake of a Nuclear Accident
There are 451 nuclear power plants in the world, with 58 more under construction, and they are located in a wide range of countries—from Argentina to India to Sweden. After the Chernobyl nuclear power plant accident in 1986, there was an increased incidence of thyroid cancer among people who were in areas affected by fallout and were in their childhood or adolescent years at the time of the accident. In the wake of the Daiichi Nuclear Power Plant accident in Fukushima, Japan in 2011, the Japan Ministry of the Environment has funded a task force (Expert Group) to make recommendations about monitoring for thyroid cancer after these rare events. Dartmouth Institute Associate Professor Louise Davies, MD, MS, who is well-known for her research on overdiagnosis, particularly as it pertains to thyroid cancer, was a member of the group.
In a commentary recently published in Lancet Oncology, the Expert Group convened by the International Agency for Research on Cancer (IARC)—the specialized cancer agency of the World Health Organization (WHO)—gave a preview of their recommendations about long-term strategies for thyroid monitoring after a nuclear power plant accident. (The full work of the expert group will be published by the IARC in October.)
The group advises against population thyroid screening after a nuclear accident, instead suggesting that communities consider offering higher risk individuals the opportunity to participate in long-term thyroid monitoring programs. “When it comes to the phrase ‘higher risk’, we identified a range of radiation exposures that might be considered high risk, rather than choosing a single number. We recognize that different countries might choose different thresholds based on their local culture and resources to run such a program. For example, choosing a low cut-off would increase sensitivity in detecting cases, while choosing a higher cutoff would result in increased efficiency in findings cases,” Davies says.
The group also recommends against population screening after a nuclear accident—defined as offering every single member of a community screening without respect to radiation exposure. Population thyroid screening, while identifying cancers that may have warranted further medical intervention, also identifies those that would not have been diagnosed or have caused any harm during the patient’s lifetime if the screening had not taken place. For example, in South Korea the diagnosed incidence of thyroid cancer increased 15-fold without a substantial change in the number of deaths due to thyroid cancer after retail screenings became common practice in the early 2000’s. Even for populations affected by nuclear accidents, screening affected populations who aren’t showing symptoms, and irrespective of thyroid radiation doses, also could result in the issues related to overdiagnosis without clear public health benefits, the Expert Group states.
For the second recommendation, the group describes what is meant by a long-term monitoring program and recommends that it include education to improve health literacy before as well as after an accident, registration of participants, centralized data collection, and organized clinical management. Unlike population thyroid screening, in which all members of a population are recruited into the program, thyroid monitoring programs should be aimed at providing high-risk individuals with information and options, so they can choose whether to undergo thyroid examinations.
“It may sound like a subtle difference between population thyroid screening and a program of thyroid monitoring, but they’re actually very different. Thyroid monitoring has the individual—rather than the population—as a starting point. The aim is to give the individual options and accurate information, so they can make a decision that is aligned with their values, preferences, and circumstances,” Davies saysThe group notes that their recommendations are meant to serve as a reference for government agencies, policymakers, and others as they develop public health policies and protocols in the wake of a nuclear accidents.
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