Men who smoke and have five or more partners with whom they perform oral sex have the highest risk of developing a type of head and neck cancer that is triggered by exposure to the human papilloma virus - known as HPV-related oropharyngeal cancer - according to research published in the leading cancer journal Annals of Oncology  today (Friday).
However, the study found that only 0.7% of men will ever develop oropharyngeal cancer in their lifetimes. The risk was much lower among women, anyone who did not smoke, and people who had less than five oral sex partners in their lifetimes.
There are over 100 different kinds of HPV but only a few are known to cause cancer; infection with HPV 16 or 18 is already known to trigger most cervical cancer, and HPV16 also causes most oropharyngeal cancer. The incidence of oropharyngeal cancer is predicted to overtake cervical cancer in the USA by 2020.
"For these reasons, it would be useful to be able to identify healthy people who are most at risk of developing oropharyngeal cancer in order to inform potential screening strategies, if effective screening tests could be developed," said Dr Amber D'Souza (PhD), associate professor at the Johns Hopkins Bloomberg School of Public Health, one of the authors of the study.
"Most people perform oral sex in their lives, and we found that oral infection with cancer-causing HPV was rare among women regardless of how many oral sex partners they had. Among men who did not smoke, cancer-causing oral HPV was rare among everyone who had less than five oral sex partners, although the chances of having oral HPV infection did increase with number of oral sexual partners, and with smoking."
The researchers analysed data from 13,089 people, aged 20-69, taking part in the National Health and Nutrition Examination Survey (NHANES) who had been tested for oral HPV infection. They used the numbers of oropharyngeal cancer cases and deaths from US registries to predict the risk of cancer from oral HPV infection. They investigated the prevalence of cancer-causing HPV found in oral rinses and the numbers of new cases of oropharyngeal squamous cell cancer (OSCC) - the commonest type of oropharyngeal cancer.
The researchers found that women who had one or no oral sex partners during their lifetimes had the lowest prevalence of oral infection with cancer-causing types of HPV: 1.8% of smokers were infected and 0.5% of non-smokers. The prevalence of infection increased slightly to 1.5% among women with two or more oral sex partners. Among men, the lowest risk group were those who had one or no oral sex partners in their lifetimes, with a prevalence of oral HPV infection of 1.5%; prevalence rose to 4% among non-smokers with two to four oral sex partners. Risk of infection rose further among men who smoked and had two to four oral sex partners, with a prevalence of 7.1%, rising to 7.4% among those who did not smoke but who had five or more oral sex partners. The prevalence of infection was highest (15%) among men who smoked and had five or more oral sex partners.
Co-author, Dr Carole Fakhry (MD), associate professor at the Johns Hopkins Department of Otolaryngology - head and neck surgery, said: "Currently there are no tests that could be used for screening people for oropharyngeal cancer. It is a rare cancer and for most healthy people the harms of screening for it would outweigh the benefits because of the problem of false positive test results and consequent anxiety. Our research shows that identifying those who have oral HPV infection does not predict their future risk of cancer well, and so screening based on detecting cancer-causing oral HPV infection would be challenging. However, we are carrying out further research of oral HPV infection in young healthy men to explore this further.
"Other research is being done on different biological markers and it is possible some of them could be used for oropharyngeal cancer screening in the future in some people; for example, they might be useful in men but not in women given their lower cancer risk. Some studies suggest people who have antibodies against cancer-causing types of HPV have an increased risk of HPV-related cancer, but these antibodies are very rare. Therefore, it is not yet clear whether they will be useful for screening. Presently, these tests are not commercially available, and are still in research labs only."
There are around 16,500 cases of oropharyngeal squamous cell carcinoma (OPSCC) every year in the USA and over 11,500 of these are HPV-related, meaning that around 70% of all OPSCC in the USA is HPV-related. The incidence of HPV-related oropharyngeal cancer is around 6.6 per 100,000 among men and 1.4 per 100,000 women.
Notes: "Understanding personal risk of oropharyngeal cancer: risk-groups for oncogenic oral HPV infection and oropharyngeal cancer", by G. D'Souza, T.S. McNeel, C. Fakhry. Annals of Oncology. doi:10.1093/annonc/mdx535