Thyroid cancer "epidemic" also occurs in low- and middle-income countries

Abstract

Thyroid cancer incidence varies greatly between and within high-income countries (HICs), and overdiagnosis likely plays a major role in these differences. Yet, little is known about the situation in low- and middle-income countries (LMICs). We compare up-to-date thyroid cancer incidence and mortality at national and subnational levels. 599,851 thyroid cancer cases in subjects aged 20-74 reported in Cancer Incidence in Five Continents volume XI from 55 countries with at least 0.5 million population, aged 20-74 years, covered by population-based cancer registration, and 22,179 deaths from the WHO Mortality Database for 36 of the selected countries, over 2008-2012, were included. Age-standardized rates were computed. National incidence rates varied 50-fold. Rates were 4 times higher among women than men, with similar patterns between countries. The highest rates (>25 cases per 100,000 women) were observed in the Republic of Korea, Israel, Canada, the United States, Italy, France, and LMICs such as Turkey, Costa Rica, Brazil, and Ecuador. Incidence rates were low (<8) in a few HICs (the Netherlands, the United Kingdom, and Denmark) and lowest (3-4) in some LMICs (such as Uganda and India). Within-country incidence rates varied up to 45-fold, with the largest differences recorded between rural and urban areas in Canada (HIC) and Brazil, India, and China (LMICs). National mortality rates were very low (<2) in all countries and in both sexes, and highest in LMICs. The very high thyroid cancer incidence and low mortality rates in some LMICs also strongly suggest a major role of overdiagnosis in these countries.

Keywords: epidemiology; incidence; medical overuse; mortality; thyroid neoplasm.

Figure 1

Age‐standardized incidence and mortality rates of thyroid cancer per 100,000, for 2008–2012, in women (a) and in men (b) aged 20–74 years. The incidence data presented originate from 27 national, 8 regional, and 20 combined regional registries. The data period was 2008–2012, except in Slovakia (2008–2010); Costa Rica and Iran, Golestan (2008–2011); Vietnam, Ho Chi Minh City (2009–2012); Latvia; Peru, Lima; and Zimbabwe, Harare (2010–2012). [Color figure can be viewed at wileyonlinelibrary.com]

Figure 2

Age‐standardized incidence rates of thyroid cancer per 100,000, for 2008–2012, by regional registry, in countries with several regional registries, in women (a) and in men (b) aged 20–74 years. The number in parentheses indicates the number of regional registries in the country. Only the names of the regional registries with the highest incidence rate in each country are shown on the plot. The incidence period was 2008–2012 for the 298 regional registries, except for the after: 2008–2010: Brazil, Florianópolis; Chile, Conception and Region of Antofagasta; Ecuador, Loja; Japan, Miyagi Prefecture; Thailand, Bangkok; Italy, Caserta, Cremona, Florence and Prado, Friuli‐Venezia Giulia, Lecco, Lombardy South Pavia, Mantua, South Tyrol, Trento, and Veneto; Spain, Albacete, Asturias, Murcia, and Navarra. 2008–2011: Algeria, Sétif; Argentina, Entre Ríos Province; Brazil, Curitiba and Poços de Caldas; China, Benxi; India, Ahmedabad and Pune; Thailand, Chonburi; France, Bas‐Rhin and Manche; Italy, Barletta, Como, Ferrara, Piacenza, Sassari, Taranto, and Umbria; Spain, Canary Islands, Ciudad Real, Cuenca, and Mallorca. 2009–2012: China, Hengdong, Huaiyin District Huai'an, and Yueyanglou; India, Kamrup Urban District; Thailand, Lopburi Province; France, Limousin. 2010–2012: China, Guangzhou, Hefei, Jiangmen, Jianhu County, Wuxi, Xianju, Xiping, Yanshi, Zhongshan City, and Zhuhai; India, Tripura and Wardha; Turkey, Erzurum. [Color figure can be viewed at wileyonlinelibrary.com]