Global burden of cancers attributable to liver flukes
Authors: Men-Bao Qian, Xiao-Nong Zhou
Journal: The Lancet Global Health (2017)

Martyn Plummer and colleagues (September, 2016)1Plummer M de Martel C Vignat J Ferlay J Bray F Franceschi S Global burden of cancers attributable to infections in 2012: a synthetic analysis.Lancet Glob Health. 2016; 4: e609-e616Summary Full Text Full Text PDF PubMed Scopus (912) Google Scholar analyse the global burden of cancers attributable to infections in 2012. Despite the relatively low attributable proportion compared with other infectious agents, liver flukes, including Opisthorchis viverrini and Clonorchis sinensis, were estimated to have caused 1300 new cases of cholangiocarcinoma in 2012. However, this number might underestimate the real situation. As described in Plummer and colleagues'1Plummer M de Martel C Vignat J Ferlay J Bray F Franceschi S Global burden of cancers attributable to infections in 2012: a synthetic analysis.Lancet Glob Health. 2016; 4: e609-e616Summary Full Text Full Text PDF PubMed Scopus (912) Google Scholar appendix, parameters applied in estimation included the baseline incidence of cholangiocarcinoma from cancer registry data in Japan, the relative risk (RR) of cholangiocarcinoma in those infected with liver flukes, and the population with liver fluke infections. However, Fürst and colleagues2Fürst T Keiser J Utzinger J Global burden of human food-borne trematodiasis: a systematic review and meta-analysis.Lancet Infect Dis. 2012; 12: 210-221Summary Full Text Full Text PDF PubMed Scopus (371) Google Scholar used a different approach and reached an annual figure for new cholangiocarcinoma cases attributable to liver flukes of nearly 7000 (table). In that study, odds ratios (ORs) of 4·39 for O viverrini and 6·12 for C sinensis were combined with the cholangiocarcinoma incidence of a population highly affected by O viverrini in northeast Thailand. In our earlier study,3Qian MB Chen YD Liang S Yang GJ Zhou XN The global epidemiology of clonorchiasis and its relation with cholangiocarcinoma.Infect Dis Poverty. 2012; 1: 4Crossref PubMed Scopus (113) Google Scholar we also attempted to analyse the cholangiocarcinoma cases attributable to C sinensis, using data from South Korea. After extrapolation to the global infected population, we estimate that more than 4700 cholangiocarcinoma cases were attributable to this organism, which approaches the figure of 5591 estimated by Fürst and colleagues2Fürst T Keiser J Utzinger J Global burden of human food-borne trematodiasis: a systematic review and meta-analysis.Lancet Infect Dis. 2012; 12: 210-221Summary Full Text Full Text PDF PubMed Scopus (371) Google Scholar (table).TableAnalyses of new annual cases of cholangiocarcinoma attributed to liver flukes worldwideNumber of infected populationRelative risk or odds ratioCases of cholangiocarcinoma attributed to infectionPlummer et al (2016)1Plummer M de Martel C Vignat J Ferlay J Bray F Franceschi S Global burden of cancers attributable to infections in 2012: a synthetic analysis.Lancet Glob Health. 2016; 4: e609-e616Summary Full Text Full Text PDF PubMed Scopus (912) Google ScholarOpisthorchis viverriniNot extracted from article7·7Not extracted from articleClonorchis sinensisNot extracted from article7·7Not extracted from articleTotal24 400 000..1300Fürst et al (2012)2Fürst T Keiser J Utzinger J Global burden of human food-borne trematodiasis: a systematic review and meta-analysis.Lancet Infect Dis. 2012; 12: 210-221Summary Full Text Full Text PDF PubMed Scopus (371) Google ScholarO viverrini8 028 5034·391323C sinensis15 313 2196·125591Total23 341 722..6914Qian et al (2012)3Qian MB Chen YD Liang S Yang GJ Zhou XN The global epidemiology of clonorchiasis and its relation with cholangiocarcinoma.Infect Dis Poverty. 2012; 1: 4Crossref PubMed Scopus (113) Google ScholarC sinensis15 110 3444·474726 Open table in a new tab The figure for the infected population in Plummer and colleagues'1Plummer M de Martel C Vignat J Ferlay J Bray F Franceschi S Global burden of cancers attributable to infections in 2012: a synthetic analysis.Lancet Glob Health. 2016; 4: e609-e616Summary Full Text Full Text PDF PubMed Scopus (912) Google Scholar analysis is similar to those of the two other studies,2Fürst T Keiser J Utzinger J Global burden of human food-borne trematodiasis: a systematic review and meta-analysis.Lancet Infect Dis. 2012; 12: 210-221Summary Full Text Full Text PDF PubMed Scopus (371) Google Scholar, 3Qian MB Chen YD Liang S Yang GJ Zhou XN The global epidemiology of clonorchiasis and its relation with cholangiocarcinoma.Infect Dis Poverty. 2012; 1: 4Crossref PubMed Scopus (113) Google Scholar and the OR is higher. Thus, their substantially lower estimation of the number of cholangiocarcinoma cases attributable to liver flukes arises from the introduction of baseline cholangiocarcinoma data from Japan. The raw data from case-control studies used to calculate combined ORs were done in liver-fluke-endemic areas. Therefore, the lower cholangiocarcinoma incidence in Japan could not represent that in the control populations in these studies. Because of inadequate studies and insufficient data, and the complex and chronic characteristics of cancers, it is challenging to capture an accurate estimate of the number of cholangiocarcinoma cases attributable to liver flukes.4Qian MB Utzinger J Keiser J Zhou XN Clonorchiasis.Lancet. 2016; 387: 800-810Summary Full Text Full Text PDF PubMed Scopus (171) Google Scholar Thus, more research is needed, which will have the added benefit of raising awareness of the importance of liver flukes in east Asia and promote control and elimination. We declare no competing interests. Global burden of cancers attributable to infections in 2012: a synthetic analysisA large potential exists for reducing the burden of cancer caused by infections. Socioeconomic development is associated with a decrease in infection-associated cancers; however, to reduce the incidence of these cancers without delay, population-based vaccination and screen-and-treat programmes should be made accessible and available. Full-Text PDF Open AccessGlobal burden of cancers attributable to liver flukes – Authors' replyWe thank Men-Bao Qian and Xiao-Nong Zhou for highlighting their concerns. Although our analysis1 focused on the four main infectious agents (human papillomavirus, hepatitis B virus, hepatitis C virus, and Helicobacter pylori) responsible for 92% of the global burden of infection-attributable cancer worldwide, we welcome any improvements for the rarer infections such as Opisthorchis viverrini and Clonorchis sinensis, which are important causes of mortality and morbidity in endemic populations. Full-Text PDF Open Access