A group of investigators from the International Agency for Research on Cancer (IARC) published in The Lancet Global Health a worldwide incidence analysis of cancer attributable to infections. They found that in 2018, an estimated 2.2 million infection-attributable cancer cases were diagnosed worldwide. They pointed out in their article that as cancer prevention is largely considered in a non-communicable disease context, there is a crucial need for resources directed towards cancer prevention programmes that target infection, particularly in high-risk populations. Such interventions can markedly reduce the increasing cancer burden and associated mortality.
The burden of cancer attributable to carcinogenic infections has been periodically assessed by the IARC. Their last publication was based on GLOBOCAN 2012 data which showed that of the 11 infectious pathogens classified as group 1 carcinogens, the four most important are Helicobacter pylori, high-risk human papillomavirus (HPV), hepatitis B virus (HBV), and hepatitis C virus (HCV), which together caused more than 90% of infection-related cancers worldwide.
Infectious pathogens are strong and modifiable causes of cancer. The aim of the latest study was to improve estimates of the global and regional burden of infection-attributable cancers to inform research priorities and facilitate prevention efforts.
The IARC team used the GLOBOCAN 2018 database of cancer incidence and mortality rates and estimated the attributable fractions and global incidence for specific anatomical cancer sites, subsites, or histological subtypes known to be associated with ten infectious pathogens classified as human carcinogens. They calculated absolute numbers and age-standardised incidence rates (ASIR) of infection-attributable cancers at the country level. Estimates were stratified for sex, age group, and country, and were aggregated according to geographical regions and World Bank income groups.
The IARC team found that, for 2018, an estimated 2.2 million infection-attributable cancer cases were diagnosed worldwide, corresponding to an infection-attributable ASIR of 25.0 cases per 100 000 person-years.
Primary causes were Helicobacter pylori (810 000 cases, ASIR 8.7 cases per 100 000 person-years), HPV (690 000, 8.0), HBV (360 000, 4.1) and HCV (160 000, 1.7).
Infection-attributable ASIR was highest in eastern Asia (37.9 cases per 100 000 person-years) and sub-Saharan Africa (33.1), and lowest in northern Europe (13.6) and western Asia (13.8).
China accounted for a third of worldwide cancer cases attributable to infection, driven by high ASIR of Helicobacter pylori (15.6) and HBV (11.7) infection.
The cancer burden attributed to HPV showed the clearest relationship with country income level from ASIR of 6.9 cases per 100 000 person-years in high-income countries to 16.1 in low-income countries.
The intuitive concept of attributing a cancer case to a given infectious pathogen is especially useful for infections that cause cancer at multiple anatomical sites, and can be combined with other diseases caused by infections.
The authors concluded that estimating the burden of cancer attributable to infection could help to raise awareness and inform recommendations for action, particularly because global cancer prevention is currently seen in the context of non-communicable diseases. It could also help to prioritise resources and monitor the long-term success of health policies, for example toward the World Health Organization goals of elimination of hepatitis and cervical cancer.
Anne Rositch of the Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health in Baltimore, MD, US wrote in an accompanied comment that four main oncogenic pathogens are either vaccine-preventable (HPV, HBV) or treatable (Helicobacter pylori, HCV) infections, and all are amenable to some level of behavioural intervention focused on reducing infection transmission. She pointed out that consideration of the role of HIV as a co-factor in the incidence and mortality of many infection-associated cancers, not taken into account in the estimates by IARC, further expands opportunities to reduce the burden of infection-associated cancers.
She concluded that effective implementation of cancer-associated infection control should be prioritised by both funders and policy makers. Infectious disease control programmes and national cancer control plans should cease being siloed, and systems approaches should be employed to identify synergies.
Reference
- De Martel C, Georges D, Bray F, et al. Global burden of cancer attributable to infections in 2018: a worldwide incidence analysis. The Lancet Global Health 2020; 8(2):e180-e190. doi: 10.1016/S2214-109X(19)30488-7.
- Rositch A. Global burden of cancer attributable to infections: the critical role of implementation science. The Lancet Global Health 2020; 8(2):e153-e154. doi: 10.1016/S2214-109X(20)30001-2.