World Oncology Forum 2015
The relationship between infections, viruses, and cancer
Dr Silvia Franceschi - International Agency for Research on Cancer, Lyon, France
There are approximately a dozen infections, including viruses, bacteria and parasites that are clearly causes of cancer. The most important are Helicobacter pylori, a bacterium that is the most important cause of stomach cancer, human papilloma virus that is the necessary cause of cervical cancer in women and also is responsible for other anogenital cancers and some cancers of the throat. Then there are two hepatitis viruses, hepatitis B and hepatitis C viruses that are responsible for the majority of liver cancer in the world and the totality, nearly, of liver cancer in poor countries.
What about the relationship between HIV and cancer?
HIV is not a carcinogenic virus as far as we know but it has a very strong adverse effect on immunity and therefore on the ability of the body to eliminate those other viruses I was mentioning that are, in turn, carcinogenic. That means that whereas HIV positive people are not at increased risk of breast cancer or prostate cancer but they do have an important increase in the risk of lymphoma, Kaposi’s sarcoma, cervical cancer, anal cancer. It is those cancers that I was mentioning as associated with carcinogenic infections.
We’ve seen the HPV vaccine – how are other infections being addressed?
I am optimistic in the long term but I wouldn’t be so happy for the moment. Let’s say that there have been substantial steps worldwide with the vaccination against hepatitis B that in this moment reach the majority of the children. HPV, papilloma virus, vaccination has been at the beginning very expensive, now it’s getting a little less expensive. It’s used more or less well in many rich countries, very well in Australia, very well in Britain, reasonably well in the United States and in Italy but, for instance, very low coverage, very low vaccination levels in France and in Germany. So there is a lot to do still in rich countries.
In poor countries HPV vaccination is only starting arriving now thanks to the sponsorship of the so-called GAVI, which is the Global Alliance for Vaccination and Immunisation which is providing subsidised HPV vaccine to the poorest countries in the world.
What needs to be looked at next with regards to infection-related cancers?
Again, just to give an idea of the numbers, one cancer out of seven in the world is caused by infections but one out of three in sub-Saharan Africa. So it’s a problem that is a sort of social injustice as it is especially heavy on the poorest population. But, again, the good side is that early diagnosis and early treatment can eliminate also hepatitis C and that the drugs, vaccines as we say, against hepatitis B and HPV that also for HIV treatment is making immunodepression due to HIV rarer and rarer. So I would say that in the world of cancer prevention, infections offer better tools for prevention, prevention of infection or cure of the infection with anti-viral or anti-bacterial treatment. So it’s a privileged field for prevention in cancer compared to other important factors like lifestyle etc.
