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1 in 6 cancers worldwide caused by infections that can be prevented or treated

One in every six cancers worldwide is caused by an infection that is preventable or treatable, according to new estimates published in the journal Lancet Oncology. The research indicates infections are attributable for approximately 2 million new cancer cases every year.

"Infections with certain viruses, bacteria, and parasites are one of the biggest and preventable causes of cancer worldwide,” lead authors Catherine de Martel and Martyn Plummer from the International Agency for Research on Cancer (IARC), France, said in a statement. They added that “application of existing public-health methods for infection prevention, such as vaccination, safer injection practice, or antimicrobial treatments, could have a substantial effect on future burden of cancer worldwide.”

Cancers caused by infections generally have a higher mortality rate than other cancers, according to the researchers.  Of the 7.5 million deaths from cancer worldwide in 2008, approximately 1.5 million were due to infections.

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.

“The burden of infection-related cancer is higher in less-developed countries,” Plummer told FoxNews.com. “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 worldwide rate of infection-related cancer has remained relatively stable compared to previous estimates from 1990 and 2002, according to Plummer.

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.

Four main infections account for 1.9 million of these types of cancer cases, including human papillomaviruses (HPV), Helicobacter pylori, and hepatitis B (HBV) and hepatitis C viruses (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.

“The numbers of cases are similar for men (990,000 cases) and women (1,100,000 cases), but the specific cancers are very different,” Plummer said. “Men do not get cervical cancer, of course, but are at much higher risk of liver and gastric cancer than women.”

Plummer said it was also important to note that these cancers can strike young and middle-aged people as well: 30 percent of infection-related cancers occur in people under the age of 50.

“One thing that infection-associated cancers have in common is that a chronic infection is required,” Plummer said.  “It takes decades for an infection to progress to cancer.  Broadly speaking, one can say that the virus or bacterium establishes a long-term infection for its own survival, but that cancer sometimes occurs as a side-effect of this attempt at cohabitation with a human host.”

However, these infections can often be treated – or even prevented – before they ever reach a cancerous stage, highlighting the need to set cancer control priorities on a national and regional basis, especially in low and middle-income countries, according to a statement from Dr. Christopher Wild, the director of the IARC.

“Progress in preventing cancer comes in three stages: understanding the mechanisms, developing effective prevention programs, and implementing these programs worldwide,” Plummer said.  “In principle, the best form of prevention for infection-associated cancer is vaccination, and there has been enormous progress in this area with the development of a vaccine against human papillomavirus (HPV).”

HPV vaccines currently protect against 70 percent of all cervical cancers and could be a major benefit to women in less-developed countries without access to cervical cancer screening, Plummer added.

“The next step is global implementation of HPV vaccination,” he said. “The GAVI alliance (Global Alliance for Vaccination and Immunization), which aims to increase access to vaccination in poorer countries, now includes support for the HPV vaccine.”

If a person has already been infected with HPV, or any of the other major cancer-related infections, he or she should speak with their doctor about the appropriate cancer screening, Plummer recommended.

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