A new report by the International Agency for Research on Cancer (IARC) in collaboration with the Aviano National Cancer Institute in Italy shows that the growing epidemic of thyroid cancer reported in recent decades in several high-income countries is largely due to over-diagnosis (ie the diagnosis of tumours that are very unlikely to cause symptoms or death during a person’s lifetime).
The article, published recently in The New England Journal of Medicine (Vaccarella S, Franceschi S, Bray F, Wild CP, Plummer M, Dal Maso L. Worldwide thyroid-cancer epidemic? The increasing impact of overdiagnosis. N Engl J Med 2016; 375 [7]: 614–7) used high-quality cancer registry data from IARC’s reference publication Cancer Incidence in Five Continents to estimate the number of over-diagnosed cases of thyroid cancer in 12 countries (Australia, Denmark, England, Finland, France, Italy, Japan, Norway, Republic of Korea, Scotland, Sweden and the USA).
“Countries such as the USA, Italy and France have been most severely affected by over-diagnosis of thyroid cancer since the 1980s, after the introduction of ultrasonography, but the most recent and striking example is the Republic of Korea,” said IARC staff scientist Dr Salvatore Vaccarella, who led the study.
In total, it is estimated that more than 470,000 women and 90,000 men may have been over-diagnosed with thyroid cancer during two recent decades in the 12 countries studied. The increasing medical surveillance and the introduction of new diagnostic techniques, such as neck ultrasonography (since the 1980s) and, more recently, computed tomography (CT) scanning and magnetic resonance imaging (MRI), have led to the detection of a large number of indolent, non-lethal diseases that exist in abundance in the thyroid gland of healthy people of any age. Most of these tumours are very unlikely to cause symptoms or death.