Root Cause of Thyroid Cancer Epidemic Due to Overdiagnosis

A new study concludes that the growing epidemic of thyroid cancer reported in several high-income countries is largely due to overdiagnosis.

Researchers at the International Agency for Research on Cancer (IARC, Lyon, France) and the Aviano National Cancer Institute (CRO; Italy) used high-quality cancer registry data to estimate the number of overdiagnosed cases of thyroid cancer in 12 countries (Australia, Denmark, England, Finland, France, Italy, Japan, Norway, Republic of Korea, Scotland, Sweden, and the USA). In all, they estimated that more than 470,000 women and 90,000 men may have been overdiagnosed with thyroid cancer during the last two decades.

The estimated fraction of overdiagnosis cases in women was 70-80% in Australia, France, Italy, and the USA, approximately 50% in Japan, the Nordic countries, England, and Scotland, and approximately 90% in South Korea. In men, the incidences reported were similar but less pronounced, with an estimated overdiagnosis of approximately 70% in France, Italy, and the Republic of Korea, 45% in Australia and the USA, and less than 25% in all other countries examined. The study was published on August 18, 2016, in The New England Journal of Medicine.

“Countries such as the USA, Italy, and France have been most severely affected by overdiagnosis of thyroid cancer since the 1980’s, after the introduction of ultrasonography, but the most recent and striking example is the Republic of Korea,” said lead author Salvatore Vaccarella, PhD, of the IARC. “A few years after ultrasonography of the thyroid gland started being widely offered in the framework of a population-based multi-cancer screening, thyroid cancer has become the most commonly diagnosed cancer in women in the Republic of Korea.”

“The drastic increase in overdiagnosis and overtreatment of thyroid cancer is already a serious public health concern in many high-income countries, with worrying signs of the same trend in low- and middle-income countries,” said Christopher Wild, MD, director of the IARC. “It is therefore critical to have more research evidence in order to evaluate the best approach to address the epidemic of thyroid cancer and to avoid unnecessary harm to patients.”

Increasing medical surveillance and new diagnostic techniques, such as neck ultrasonography, 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 tumors are very unlikely to cause symptoms or death during the lifetime of the patient.

Related Links:
International Agency for Research on Cancer
Aviano National Cancer Institute