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Growing risk of throat cancer from oral sex

An increase in oropharyngeal cancer (the area of the tonsils and back of the throat) over the past 20 years is being directly attributed to the sexually transmitted human papillomavirus (HPV) – which is also the main cause of cancer of the cervix – the main risk factor being oral sex.

In fact, writes Professor Hisham Mehanna, University of Birmingham UK, in The Conversation, oropharyngeal cancer has now become more common than cervical cancer in the US and the UK.

He writes:

People with six or more lifetime oral-sex partners are 8.5 times more likely to develop oropharyngeal cancer than those who do not practise oral sex.

Behavioural trends studies show that oral sex is very prevalent in some countries, mainly in the West.

In a study that my colleagues and I conducted in almost 1 000 people having tonsillectomy for non-cancer reasons in the UK, 80% of adults reported practising oral sex at some point in their lives. Yet, mercifully, only a small number of them develop oropharyngeal cancer. Why that is, is not clear.

The prevailing theory is that most of us catch HPV infections and are able to clear them completely. However, a small number of people are unable to get rid of the infection, maybe due to a defect in a particular aspect of their immune system.

In those patients, the virus is able to replicate continuously, and over time, integrates at random positions into the host’s DNA, some of which can cause the host cells to become cancerous.

HPV vaccination of young girls has been implemented in many countries, including South Africa, to prevent cervical cancer. There is now increasing, albeit as yet indirect evidence, that it may also be effective in preventing HPV infection in the mouth.

There is also some evidence to suggest that boys are also protected by “herd immunity” in countries where there is high vaccine coverage in girls (more than 85%). Taken together, this may hopefully lead, in a few decades, to the reduction of oropharyngeal cancer.

That is well and good from a public health point of view, but only if coverage among girls is high – more than 85% – and only if one remains within the covered “herd”. It does not, however, guarantee protection at an individual level – and especially in this age of international travel – if, for example, someone has sex with someone from a country with low coverage.

It certainly does not afford protection in countries where vaccine coverage of girls is low, for example, the US where only 54.3% of adolescents aged 13 to 15 had received two or three HPV vaccination doses in 2020.

Boys should have the HPV vaccine too

This has led several countries, including the UK, Australia and the US, to extend their national recommendations for HPV vaccination to include young boys – called a gender-neutral vaccination policy.

But having a universal vaccination policy does not guarantee coverage. There is a significant proportion of some populations opposed to HPV vaccination due to concerns about safety, necessity, or, less commonly, concerns about encouraging promiscuity.

Paradoxically, there is some evidence from population studies that, possibly in an effort to abstain from penetrative intercourse, young adults may practise oral sex instead, at least initially.

The coronavirus pandemic has brought its own challenges, too. First, reaching young people at schools was not possible for while. Second, there has been an increasing trend in general vaccine hesitancy, or “anti-vax” attitudes, in many countries, which may also contribute to a reduction in vaccine uptake.

As always when dealing with populations and behaviour, nothing is simple or straightforward.

Mehanna is a professor at the Institute of Cancer and Genomic Sciences, University of Birmingham, England.

Study details

Human Papillomavirus (HPV) Vaccine Effectiveness and Potential Herd Immunity for Reducing Oncogenic Oropharyngeal HPV-16 Prevalence in the United Kingdom: A Cross-sectional Study

Hisham Mehanna, Tyler  Bryant, Jaspreet Babrah, Karly Louie, Jennifer Bryant, Rachel Spruce, Nikolaos Batis, Oladejo Olaleye, June Jones, Linda Struijk, Anco Molijn, Alex Vorsters, Dominique Rosillon, Sylvia Taylor, and Gypsyamber D’Souza.

Published in Clinical Infectious Diseases on 15 October 2019.

Background
Oropharyngeal cancer incidence is rapidly rising due to human papillomavirus (HPV) type 16 infection. The dearth of data on effectiveness of national female-only vaccination programs in preventing oral HPV infection and potential herd immunity in unvaccinated males has resulted in considerable controversy regarding the need to vaccinate males, especially in countries with high female vaccination coverage.

Methods
Subjects aged 0–65 years undergoing tonsillectomy for nonmalignant indications were recruited in 6 hospitals in the United Kingdom. Oral samples were collected as follows: oral rinse, tongue base, and pharyngeal wall brushes, then tonsil tissue (tonsillectomy). Vaccination data were obtained from regional health authorities. All samples were centrally tested for HPV DNA by polymerase chain reaction.

Results
Of 940 subjects, 243 females and 69 males were aged 12–24 years (median age, 18.6 years), with 189 (78%) females and no males vaccinated against HPV. Overall, oropharyngeal HPV-16 prevalence was significantly lower in vaccinated versus unvaccinated females (0.5% vs 5.6%, P = .04). In contrast, prevalence of any oropharyngeal HPV type was similar in vaccinated and unvaccinated females (19% vs 20%, P = .76). Oropharyngeal HPV-16 prevalence in unvaccinated males was similar to vaccinated females (0% vs 0.5%, P > .99), and lower than unvaccinated females (0% vs 5.6%, P = .08).

Conclusions
Our findings indicate that the UK female-only vaccination programme is associated with significant reductions in oropharyngeal HPV-16 infections. These are also the first data to suggest potential herd immunity from female-only vaccination against oropharyngeal HPV infection in contemporaneously aged males.

 

CID article – Human Papillomavirus (HPV) Vaccine Effectiveness and Potential Herd Immunity (Open access)

 

The Conversation article – Oral sex is now the leading risk factor for throat cancer (Creative Commons Licence)

 

See more from MedicalBrief archives:

 

Vaccine could have prevented over 90% of HPV-related cancers

 

World-first: Saliva test detects a hidden throat cancer

 

HPV vaccine significantly lowers infection rates in teen girls — CDC study

 

 

 

 

 

 

 

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