Over the past twenty years, throat cancer has increased rapidly in the west, to the extent that some have called it an epidemic. This was due to a significant increase in a specific type of throat cancer called oropharyngeal cancer (the area of the tonsils and the back of the throat). The main cause of this cancer is the human papilloma virus (HPV), which is also the main cause of cervical cancer. Oropharyngeal cancer is now more common than cervical cancer in the US and UK.
HPV is transmitted sexually. For oropharyngeal cancer, the main risk factor is the number of sexual partners in a lifetime, especially oral sex. Those who have six or more oral sex partners in their lifetime are 8.5 times more likely to get oropharyngeal cancer than those who do not practice oral sex.
Studies of behavioral trends show that oral sex is very common in some countries. In a study by my colleagues and myself of nearly 1,000 people who had tonsillectomy for non-cancer reasons in the UK, 80% of adults reported having oral sex at some point in their lives. But, mercifully, only a small number of those people 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 clear the infection, possibly due to a defect in some aspect of their immune system. In those patients, the virus can replicate continuously, and over time randomly integrates into the host’s DNA, some of which can cause host cell cancer.
HPV vaccination of young girls has been implemented in many countries to prevent cervical cancer. There is now increasing, although still circumstantial, evidence that it may also be effective in preventing oral HPV infection. There is also some evidence to suggest that boys are protected by “herd immunity” in countries with high vaccine coverage among girls (over 85%). Taken together, this will hopefully lead to a reduction in oropharyngeal cancer in a few years.
That’s all well and good from a public health point of view, but only if coverage among girls is high – over 85%, and not one person within the “herd” remains covered. However, it does not 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 provide protection in countries with low vaccine coverage for girls, for example, in the US only 54.3% of teenagers aged 13 to 15 years received two or three doses of HPV vaccination in 2020.
Boys should also have the HPV vaccine
This has led to many countries, including the UK, Australia and the US, expanding their national HPV vaccination recommendations to include young boys – known as a gender-neutral vaccination policy.
But a universal vaccination policy does not guarantee coverage. A significant percentage of some populations are opposed to HPV vaccination because of safety concerns, necessity, or, less often, because of concerns about encouraging excess.
Paradoxically, there is some evidence from population studies, that young adults may practice oral sex instead, at least initially, in an attempt to refrain from penetrative intercourse.
The coronavirus pandemic has brought its own challenges, too. First, it was not possible for a period of time to contact young people in schools. Second, there is a growing trend of general vaccine hesitancy, or “anti-vacc” attitudes, in many countries, which may contribute to declining vaccine uptake. .
As always when dealing with populations and behavior, nothing is simple or straightforward.
This article from The Conversation is republished under a Creative Commons license. Read the original article.
Hisham Mehanna consults for MSD and Merck. He receives funding from Cancer Research UK, the National Institute for Health Research and the MRC, as well as Astra Zeneca, GSK, and GSK Bio. He is a consultant to the Oracle Trust, a head and neck patient advocacy charity.