Can Infections Cause Cancer?

One in every six cancers worldwide is caused by a bacterial, fungal, parasitic, or viral infection that is preventable or treatable, according to new estimates published in the journal, Lancet Oncology.   

The research, from the International Agency for Research on Cancer in France, indicates infections are attributable to approximately 2 million new cancer cases every year.

The four main infections that account for 1.9 million of these types of cancer cases are:

• Human papillomaviruses (HPV)
• Helicobacter pylori
• Hepatitis B (HBV)
• Hepatitis C (HCV)

The most common cancers caused by these infections were gastric, liver, and cervical cancers. In women, cervical cancer accounted for 50 percent of the infection-related cancer burden, while in men, liver and gastric cancers accounted for more than 80 percent of the burden.

Of the 7.5 million deaths from cancer worldwide in 2008, approximately 1.5 million were due to infections.

The authors of the study claim that the "application of existing public-health methods for infection prevention, such as vaccination, safer injection practices, or antimicrobial treatments, could have a substantial effect on the future burden of cancer worldwide."

Cancers caused by infections generally have a higher mortality rate than other cancers, according to the researchers.   To measure the rates, the researchers conducted an analysis that included data on 27 cancers in 184 countries.  They found 16 percent of all cancers worldwide stemmed from infections, however the rates varied by region.

In less-developed countries, 22.9 percent of cancers are due to infection, whereas in more-developed countries the figure is 7.4 percent.   

The highest proportion of infection-related cancers was found in sub-Saharan Africa, where one in three cancers is caused by an infection (32.7 percent).  In comparison, figures from the U.S. and Canada indicate that 4 percent of cancers in North America are due to infection.

The countries with the lowest rates of infection-related cancers are Australia and New Zealand, with estimates of 3.3 percent.

The numbers of cases are similar for men (990,000 cases) and women (1,100,000 cases), but the specific cancers are very different.

One thing that infection-associated cancers have in common is that a chronic infection is required. It takes decades for an infection, which causes chronic inflammation, to progress to cancer.  

As this new research indicates, control of cancer can be partially accomplished by effective infection control.

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