Overdiagnosis of thyroid cancer in adolescents

Overdiagnosis of thyroid cancer in adolescents. There are many controversies about the early detection and early treatment of thyroid cancer. Ultrasound screening of thyroid is not harmless, but harmful to children without any symptoms.

The article “Overdiagnosis of Thyroid Cancer in Adolescents” published by Toru Takano in 2020 is a continuation of that review. The writing background of these two articles is the Fukushima Health Management Survey (FHMS) research project launched after the Fukushima nuclear power plant accident in 2011 for Fukushima residents.

After analyzing the relevant data, Toru Takano wrote this article and published it in the “European Thyroid Journal” (Eur Thyroid J. 2020 May; 9(3): 124–131.). The first half of the article is mainly about data introduction and mechanism analysis. The following is an excerpt from the latter part of the article.

Overdiagnosis of thyroid cancer in adolescents

Toru Takano, Department of Metabolic Medicine, Faculty of Medicine, Osaka University

[Mechanism of overdiagnosis of juvenile thyroid cancer]

Overdiagnosis refers to the discovery of a disease, but this disease will not cause any harm to the patient during the life of the patient. According to autopsy data, it is estimated that occult thyroid cancer in adolescents and its prevalence are rising sharply after puberty and before the age of 30. On the other hand, the prevalence of thyroid cancer in adolescents is very low, and it grows very slowly, reaching a peak in the 40s or 50s. Therefore, over-diagnosis of thyroid cancer is likely to occur in the younger generation of people from late adolescence to early 30s. We should remember that based on the above considerations, the detection of small cancers in adolescents by ultrasonography mostly leads to overdiagnosis rather than early diagnosis.

[Pros and Cons of Adolescent Thyroid Screening Based on Ultrasound]

Due to the good prognosis of adolescent thyroid cancer, ultrasound screening is unlikely to reduce cancer-related mortality. In addition, it is not clear whether early ultrasound detection can improve the quality of life by preventing local or distant metastases or reducing recurrence rates. Therefore, it is difficult to determine the benefits of ultrasound-based thyroid screening for young people.

The main harm of ultrasound thyroid screening is overdiagnosis. Over-diagnosis is more harmful to young people than older people. Although the current data is scarce, it can be easily speculated that stigmatizing patients with thyroid cancer is the most serious threat to children and young adults. People who are diagnosed with thyroid cancer are regarded as “juvenile cancer” patients. Most people think that juvenile cancer is serious and fatal, but juvenile thyroid cancer is actually a rare exception.

In reality, children and young adults with thyroid cancer may have to live as patients with life-threatening diseases. This stigma may affect their school and work life, and even cause unexpected obstacles when they choose a spouse. In fact, the biggest concern of children diagnosed with thyroid cancer in Fukushima, Japan and their parents is not their health problems, but their marital problems.

When we only focus on health issues, the harm of overdiagnosis of thyroid cancer in young people is actually often underestimated. The over-diagnosis of thyroid cancer is closely related to the human rights of children and young adults. Children and young adults suffering from thyroid cancer may have far greater psychological, social, and economic effects than physical. Children diagnosed with thyroid cancer after the Chernobyl accident are at high risk of attempted suicide. Although it is difficult to conclude that the Chernobyl suicide is related to the diagnosis of thyroid cancer; however, it cannot be ruled out as a conducive response. The possibility of stimulus.

In addition, it is difficult for children and young adults with thyroid cancer to perform active monitoring, and this active monitoring is now an acceptable recommended alternative to surgical treatment for adult papillary thyroid microcarcinoma. As far as children are concerned, such monitoring may last for more than half a century. Children with thyroid cancer must experience many life events that may change their lifestyle, such as entering college, employment, marriage or pregnancy. With every life event, they worry and question whether it is correct not to remove thyroid cancer. This long-term active surveillance forces children to bear a heavy burden. In fact, in Fukushima, most small thyroid cancers in children that can only be detected by ultrasound have to undergo surgery.

The US Preventive Services Task Force summarized the advantages and disadvantages of ultrasound-based thyroid screening and concluded that ultrasound screening of asymptomatic individuals is not recommended because it does more harm than good. Taking into account the above discussion, this conclusion is also valid for children. Ultrasound screening of asymptomatic children should be avoided.

The recent guidelines of some countries and regions have come to a consistent conclusion. The conclusion is that they have no confidence in the benefits of ultrasound screening, even in the follow-up of children after high-dose thyroid radiation exposure. Recently, the International Agency for Research on Cancer recommended not to perform population thyroid screening after a nuclear power plant accident, because the harms outweigh the benefits. Therefore, FHMS (Fukushima Health Management Survey) may be the last thyroid screening project, even if another nuclear power plant accident occurs in the future.

[Ethical Issues of Thyroid Screening Project]

As happened in South Korea and the United States, overdiagnosis is always accompanied by some medical ethical issues. As mentioned above, thyroid screening may do more harm than good for children. The purpose of Fukushima thyroid screening is to understand the impact of radiation on residents’ health and reduce residents’ anxiety. However, neither has directly benefited children who are targets of thyroid screening. Medical research on humans must follow the Declaration of Helsinki, and it is recommended to avoid research that does more harm than good to the subjects. Therefore, from an ethical point of view, it is difficult to justify Fukushima’s current thyroid screening program.

In addition, the lack of informed consent inspections conducted during school hours may be regarded as a mandatory inspection or may violate the Declaration of Helsinki. The reason for these situations is that when FHMS began to implement thyroid screening in 2011, it was generally believed that thyroid screening in the United States would not harm children. However, recent data on the natural history of thyroid cancer in adolescents has changed this optimistic view. According to medical ethics, the local government should reconsider the current situation and make appropriate changes to the current agreement.

【Conclusion】

Early detection and early treatment of thyroid cancer is no longer a golden rule. Ultrasound screening of thyroid is not harmless, but harmful to children without any symptoms. In a previous paper, in order to prevent the expansion of overdiagnosis, I proposed the following three responses:

• First, experts must disclose their honest views and do not cause any misleading due to conflicts of interest;
• Second, residents must educate themselves to avoid the spread of fear and popular paradoxes;
• Third, all relevant personnel should give priority to protecting children from over-diagnosis harm to their own interests.

We should not hesitate to continue discussing over-diagnosis. Everyone working on a thyroid screening project in Fukushima should remember that the first priority is to protect the health and welfare of the child, not his/her own practices.

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