An estimated 13% of all cancer cases in 2018 may be attributable to infections, concludes a new global survey.
This extrapolates to about 2.2 million cancer cases that were diagnosed worldwide, corresponding to an age-standardized incidence rate (ASIR) of 25 cases per 100,000 person-years.
The primary causes were Helicobacter pylori, human papillomavirus (HPV), hepatitis B virus (HBV), and hepatitis C virus (HCV).
Of note, a third of all global cancer cases attributable to infection occurred in China, which accounted for 42% of cancers caused by H pylori and for 69% of those caused by HBV.
"The present work estimates for the first time incidence rates of infection-attributable cancer in 2018 at an individual country level," write the authors, led by Catherine de Martel, MD, of the Infections and Cancer Epidemiology Group at the International Agency for Research on Cancer, France.
"Our study can help to raise awareness and inform recommendations for action against cancer, which tends to be viewed as a non-communicable disease," they add.
The findings were published online December 17 in the Lancet Global Health.
A causal association between certain infections and human malignancies is already well established, the authors comment. Previous research by de Martel and her group found that H pylori, HBV, HCV, and HPV were responsible for 1.9 million of 12.7 million cancer cases reported in 2008. Most of these were gastric, hepatic, and cervix uteri cancers.
For the current analysis, the authors used the GLOBOCAN 2018 database of cancer incidence and mortality rates. They estimated the attributable percentages and global incidence for specific cancers that have already been associated with infectious pathogens. The absolute numbers and ASIR were calculated at the country level and were stratified by sex, age group, and country.
Their results showed that H pylori was responsible for 810,000 new cancer cases in 2018 (ASIR, 8.7 cases per 100,000 person-years), primarily underlying noncardia gastric adenocarcinoma. This was followed by HPV, responsible for 690,000 new cases (ASIR, 8.0 cases per 100,000 person-years), primarily causing cervix uteri carcinoma.
HBV contributed to 360,000 new cases (ASIR, 4.1), and HCV was responsible for 160,000 new cases (ASIR, 1.7), both primarily causing hepatocellular carcinoma.
Other infectious agents, including Epstein-Barr virus, human T-cell lymphotropic virus type 1, human herpesvirus type 8 (also known as Kaposi sarcoma herpesvirus), and parasitic infections contributed to the remaining 210,000 new cases.
Variation by Sex and Income
Overall, men and women were equally affected by cancers caused by infections, but the types of pathogens and cancers varied by sex.
There was also considerable variation by geographic region. Eastern Asia had the highest rates of infection, with 37.9 cases per 100,000 person-years, followed closely by sub-Saharan Africa (33.1). Conversely, the lowest number of cases was in northern Europe (13.6) and western Asia (13.8).
China accounted for 780,000 (35%) of the new infection-attributable cases in 2018. Of those, 340,000 were linked to H pylori, and 250,000 to HBV. South Korea also had a very high incidence of cancer caused by H pylori infection (ASIR, 35.2 cases per 100,000 person-years), as did Japan (23.8). There was also a high incidence of cancer cases related to HBV in South Korea (8.6).
Cervix uteri carcinoma accounts for approximately 80% of cancers (n = 570,000 cases) that could be attributed to HPV. Women were the most affected by HPV, accounting for 90% of the 690,000 attributed cases globally. These proportions were highest in the lowest-income countries.
In contrast, the proportions of the other types of HPV-related anogenital cancers, along with head and neck cancers, were higher in high-income countries, with a greater proportion seen in men.
"It should be emphasized that the data we present here are a snapshot of the burden of cancer attributable to infections worldwide in 2018, and comparisons with previous results are not possible because of changes in data sources, notably for cancer incidence estimates, as well as other methodological modifications," the authors write.
The study was funded by the International Agency for Research on Cancer. The authors report no relevant financial relationships.
Lancet Glob Health. Published online December 17, 2019. Full text
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