Harm of overdiagnosis or extremely early diagnosis behind trends in pediatric thyroid cancer.

Abstract

We are concerned that the momentum gained toward preventing the overdiagnosis of thyroid cancer will decrease because of the encouragement of studies concerning environmental risk factors, as discussed in the article by Bernier et al.1 It is important to note that in an editorial, Chen and Davies2 mentioned that there is a need to examine whether the increase in pediatric thyroid cancer is attributable to overdiagnosis, even though there might be new genetic, environmental, or dietary causes of thyroid cancer. Furthermore, Goldenberg3 indicated that overdiagnosis absolves researchers of the duty to seek causes of the real increase in thyroid cancer. Overdiagnosis is a serious problem that should be considered during the process of diagnosing cancer. Every clinician and scientist should be aware that the diagnosis of indolent cancer in a patient's lifetime (overdiagnosis) leads to physical and psychological burdens, as well as individual and social economic costs during the process of diagnostic examinations and subsequent potential overtreatment. Living as a patient with cancer over a lifetime involves not only anxiety and unhappiness, but also amplified public risk perception of the disease. In addition, there are social disadvantages and discrimination faced when obtaining employment, insurance coverage, and a marriage partner.4, 5 The harm of overdiagnosis in young people is more serious because of their longer lifespan,5 and the experience of overdiagnosis can negatively affect decision making in their lives. These disadvantages must be avoided if cancer is overdiagnosed. Even in the case of a real increase in the incidence of pediatric thyroid cancer without overdiagnosis, extremely early diagnosis also is considered to be harmful. This is because of the good prognosis of patients diagnosed with pediatric thyroid cancer and the possibility of growth arrest in thyroid cancer in young individuals.6 We have no evidence that the extremely early diagnosis of thyroid cancer decreases mortality. Therefore, an extremely early diagnosis could have harms similar to those of overdiagnosis (physical, psychological, economic, and social issues). Extremely early diagnosis makes patients experience such problems over a longer lifetime. However, medical professionals and the public tend to regard early diagnosis as a good thing. There is a misinterpretation that an early diagnosis would be more beneficial than harmful for any type of cancer. Therefore, we need to consider the balance between benefits and harms in the early diagnosis of pediatric thyroid cancer. Bernier et al1 described the importance of investigating environmental, dietary, and genetic factors as contributors to the rising incidence of pediatric thyroid cancer. This would require large-scale epidemiological studies because of the rarity of these cancers. In Fukushima, an epidemiological survey demonstrated that using highly sensitive ultrasonography for thyroid cancer screening led to overdiagnosis and/or extremely early diagnosis in the young population.7 Surveys should be implemented with special notes made of the conditions for which benefits overweigh harms by avoiding overdiagnosis and extremely early diagnosis, and also by effective communication with patients and their guardians. We strongly hope that the article by Bernier et al1 will be useful for the prevention of overdiagnosis and the promotion of primary prevention without the extremely early diagnosis of pediatric thyroid cancer. No specific funding was disclosed. The authors made no disclosures.