Cancers and infections
Marian Pitts (pictured) and Jack Wallace
This piece was originally published in The Conversation 21 May, 2012.
Australia has had a pioneering role in the discoveries that underpin our understanding that some cancers can be caused by infectious agents. But we still face many problems that could be solved if we only had the will.
A recent article in The Lancet reported the results of a systematic review of the global burden of cancers attributable to infectious diseases. The review looked at incidence rates for 27 cancers in 184 countries. Of the estimated 12.7 million new cases of cancer worldwide in 2008, around two million were attributable to infectious diseases.
The four main infections that caused these were Helicobactor pylori, human papillomavirus, hepatitis B and hepatitis C. Overall, the study found that 16% of all cancers were attributable to infections; the good news is that many of these infection-related cancers are preventable.
In 2005, the Nobel Prize in Physiology/Medicine was awarded jointly to two scientists from Western Australia – Barry J. Marshall and J. Robin Warren. The prize was for their discovery of the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease.
Rates of helicobacter pylori are reducing in most developed countries, including Australia, as a result. But the prevalence of H. pylori in Indigenous communities is two to three times higher than that in the non-Indigenous Australian population, with particularly high rates in rural and remote communities.
As recently as December 2011, there was still concern that Aboriginal and Torres Strait Islanders were at far greater risk of a range of gastric problems, including related cancers than their non-Indigenous counterparts.
Hepatitis B infection can be prevented with a safe and effective vaccine and much of Australia’s success results from the implementation of a vaccination program. But there are still populations that remain at higher risk of this infection. These include people born in countries where the vaccination program hasn’t been as effectively implemented or where implementation is recent.
This, however, is changing. China, the country with the most number of people infected with chronic hepatitis B in the world, has reduced the number of children with the illness to less than 1% of those under the age of five through vaccination.
But many of our neighbours need help vaccinating against hepatitis B. A 1998 letter to the British Medical Journal (BMJ) argued that the global burden of hepatitis B could be reduced more cost effectively if vaccination was targeted at highly endemic areas. In practical terms, this means that there’s a cost benefit for Australia to support vaccinating people in our region.
Reducing the transmission of hepatitis C is more challenging. While Australia was quick to secure the blood supply and support the operation of needle and syringes programs to prevent further transmission, an unsatisfactorily large number of people are still being infected with hepatitis C.
The association between hepatitis C transmission and unsterile injecting drug use (together with hostile attitudes and beliefs within Australia and the region about drug use), result in a reluctance to take the steps to reduce further transmission.
Key challenges remain for Australia to reduce the cancers associated with both hepatitis B and hepatitis C infections. It’s been estimated that about one-third of people in Australia with chronic hepatitis B remain undiagnosed and unaware that they’re infected. Added to this figure is the fact that less than 2% of the people who know they have the infection actually access hepatitis B specialist services.
Similarly, while Australia has been relatively successful in diagnosing people infected with hepatitis C, access to clinical services remains unspectacular.
In 2010, the World Health Assembly adopted a resolution acknowledging the impact of chronic viral hepatitis and identifying a series of interventions to address it. But most governments in our region have made slow, if any progress, in developing a comprehensive and coordinated response.
Australia was the first country in the world to have a national strategic approach to hepatitis C, and in 2010 developed its first National Hepatitis B Strategy. But while these strategies provide the framework for implementing a range of programs, the lack of funding to support them fundamentally limits their effectiveness.
In 2007, Australia was the first country to introduce the Gardasil vaccine free to girls aged 12 and 13, via a school-based program. The success of this program is already apparent in reducing the incidence of cervical abnormalities in young women who have received the vaccination.
The current HPV vaccination program will ensure that cancers of the cervix related to some types of HPV will continue to fall. But there’s increasingly strong evidence (some of which was included in this review) that HPV is also associated with penile and anal cancers, as well as oropharangeal (mouth and throat) cancers.
These cancers affect men, and the Pharmaceutical Benefits Advisory Committee (PBAC) last year recommended the Gardasil vaccine be given to boys aged 12 to 13 in a school-based program.
The Federal Government is considering the recommendation, but to date, there still hasn’t been an official announcement about the measure. We don’t know how much longer we need to wait before the government rolls out the vaccine to young men.
So where does this leave with infection-related cancers? There’s a pattern here – excellent beginnings, but a lack of follow through. We know how to prevent these cancers and we have the tools, but do we yet have the will?
Professor Marian Pitts is Director of La Trobe University’s Australian Research Centre in Sex, Health and Society (ARCSHS) and Jack Wallace is a Research Fellow at ARCSHS.