Over the past two decades, there has been a rapid increase in throat cancer in the West, to the point that some have called it an epidemic. This is due to a large increase in a specific type of throat cancer called cancer of the oropharynx (the area of the tonsils and the back of the throat). The main cause of this cancer is the human papillomavirus (HPV), which is also the main cause of cervical cancer. Oropharyngeal cancer has now become more common than cervical cancer in the US and UK.
HPV is sexually transmitted. For oropharyngeal cancer, the primary risk factor is lifetime number of sexual partners, especially oral sex. Those who have had six or more oral sex partners in their lifetime are 8.5 times more likely to develop oropharyngeal cancer than those who do not practice oral sex.
Behavioral trend studies show that oral sex is very common in some countries. In a study my colleagues and I conducted of nearly 1,000 people undergoing tonsillectomy for non-cancerous reasons in the UK, 80% of adults said they had had oral sex at some point in their lives. Yet, fortunately, only a small number of these people develop oropharyngeal cancer. Why this is, is unclear.
The prevailing theory is that most of us catch HPV infections and are able to clear them completely. However, a small number of people fail to clear the infection, possibly due to a defect in a particular aspect of their immune system. In these patients, the virus is able to continuously replicate and, over time, integrates into random positions in the host’s DNA, some of which can cause host cells to become cancerous.
HPV vaccination of young girls has been implemented in many countries to prevent cervical cancer. There is now growing, albeit still indirect, evidence that it may also be effective in preventing HPV infection in the mouth. There is also evidence to suggest that boys are also protected by ‘herd immunity’ in countries where girls’ vaccination coverage is high (over 85%). Taken together, this could hopefully lead in a few decades to the reduction of oropharyngeal cancer.
This is great from a public health perspective, but only if coverage among girls is high – over 85%, and only if one stays in the covered “herd”. This does not, however, guarantee protection at the individual level – and especially in the age of international travel – if, for example, someone has sex with someone from a country with low coverage. It certainly does not offer protection in countries where vaccination coverage for girls is low, for example in the United States where only 54.3% of adolescents aged 13 to 15 had received two or three doses of the vaccine against HPV in 2020.
Boys should also get the HPV vaccine
This has led several countries, including the UK, Australia and the US, to extend their national HPV vaccination recommendations to include young boys – a so-called gender-neutral vaccination policy. .
But having a universal vaccination policy does not guarantee coverage. There is a significant proportion of certain populations who oppose HPV vaccination due to concerns about safety, necessity, or, less frequently, due to concerns about encouraging promiscuity.
Paradoxically, some population studies show that, perhaps in an effort to abstain from penetrative sex, young adults may practice oral sex instead, at least initially.
The coronavirus pandemic has also brought its own challenges. First, reaching young people in schools has not been possible for some time. Second, there has been a growing trend of general vaccine hesitancy, or “anti-vax” attitudes, in many countries, which may also be contributing to a reduction in vaccination.
As always when it comes to populations and behaviors, nothing is simple or straightforward.
Hisham MehannaProfessor, Institute of Cancer and Genome Sciences, University of Birmingham
This article is republished from The Conversation under a Creative Commons license. Read the original article.