Travelling to work early Friday morning, I came across this article in the Metro.
The article is rather heavy on startling, attention-grabbing statements and a bit low on facts. It claims that a virus spread by oral sex might be responsible for the rise in throat cancer in men. The wording used somewhat implies that women are therefore responsible for 'infecting' men with throat cancer. After all, no one is worried about any rise in throat cancer in women.
I couldn't really identify any un-sullied facts in this widely read article, so I set about uncovering the research behind the article.
Where did this story originally come from?
The story is based on an editorial in the British Medical Journal, written by throat cancer specialists. The editorial highlighted an increase in the numbers oropharyngeal squamous cell carcinoma in the UK. This is a cancer of the lining of the mouth and throat.
The specialists also discussed studies from other countries that show an increase in the proportion of human papilloma virus (HPV)-related throat cancers. That means the number of cancers that when analysed, contained particles of HPV.
Although the editorial reported on a very small number of studies, it showed that there may be a need to investigate the incidence of HPV-related throat cancers in the UK, and to see if HPV-related cancers should be treated differently to non-HPV-related throat cancers. This is because more throat cancers these days seem to contain HPV than 30 years ago, and there seems to be a difference in how many people survive treatment of throat cancers that do and do not contain HPV.
This editorial was written by Hisham Mehanna, director of the Institute of Head and Neck Studies and Education at University Hospital, Coventry, and colleagues at the University of Liverpool, Université Catholique de Louvain and the University of Texas. The editorial was commissioned and published by the British Medical Journal and importantly, it was not externally peer-reviewed. This means that the content has not been read and approved by other experts in the field. This means that their claims are not substantiated by other experts and really only represent the opinion of a number of individuals.
What was the main point of the editorial?
The main focus of the editorial was to highlight the increasing rates of throat cancer in the UK, and the potential increase in cases where HPV is found in the tumour tissue. The specialists looked at a particular type of throat cancer called oropharyngeal squamous cell carcinoma and found that the incidence has increased from 7 per 100,000 men to 11 per 100,000 between 1989 and 2006.
Although this was the main point of the original editorial, the main point of the resulting media speculation has been the link to oral sex and the cervical cancer vaccination.
What evidence did they use to support their claims?
The main claim is that the increase in cases of oropharyngeal squamous cell carcinoma could be due to an increased prevalence of HPV.
They cited a Swedish study as the main support for this. This study looked at how many of these tumours contained HPV and found that although in 1970s only 23.3% of biopsies were positive for HPV, this figure rose to 93% between 2006 and 2007. A similar American study found slightly lower figures of 60-70% of tumours containing HPV.
The authors go on to mention that cancers containing HPV are slightly easier to treat with a survival rate of 87-5-95% compared to 62-67% in non-HPV-related tumours.
This means there is the potential that these two types of tumour - squamous cell carcinoma containing HPV and squamous cell carcinoma not containing HPV - may actually act differently, and require different treatments. May be they should be classified separately. There is currently no research on this.
What has this got to do with oral sex?
The authors do not substantiate the link between oral sex and HPV transmission. This seems to stem from the knowledge that HPV may be sexually transmitted. It seems to only have been applied to female to male transmission, completely excluding male to male, male to female and female to female.
The authors seems to feel that the link to oral sex is supported by the finding that a higher number of life partners correlates with an increased risk of throat cancer. This correlation was a 'borderline' finding and barely supportable by statistical analysis.
The authors do not comment on the main, established risk factors for oropharyngeal squamous cell carcinoma which are alcohol and smoking. It would seem obvious that a higher number of life partners implies a greater number of separations and periods of stress, which in turn might correlate with a higher usage of alcohol and tobacco. But no-one has commented on that.
The authors have not looked at sexual practices over the last thirty years to see whether they have changed. They have also not looked at rates of sexually transmitted HPV infection.
What about cervical cancer vaccination in boys to protect men from throat cancer?
There is no evidence that the current HPV vaccination offered to girls to protect them from cervical cancer needs to be given to boys. Even if HPV were found to ba causative agent for throat cancer, vaccinating girls should have an appreciable impact on incidence.
- Researchers have found that the rates of throat cancer in men have increased over the last thirty years or so. They do not comment on rates in women.
- Researchers have found that more samples of throat cancer contain HPV than thirty years ago.
- There is no evidence to suggest that HPV causes throat cancer.
- There is some evidence that tumours containing HPV react differently to treatment than those that do not.
- There is no evidence that increased rates of throat cancer are due to HPV transmission via oral sex.
- There is no evidence to suggest whether sexual HPV transmission has increased over the last 30 years.
- There is no evidence to suggest whether vaccinating either girls or boys will have any effect on rates of throat cancer.
The newspaper article that had caught my eye, had taken a slither of fact from this editorial, and created a series of statements that were linked to, rather than supported by the evidence. And the editorial itself had made some startling, unsubstantiated leaps of thinking. But this is an interesting area of work, and may provide important clues that help us to managed throat cancer more effectively in the future.