Men who smoke and have had five or more oral sex partners are at the greatest risk of developing a type of head and neck cancer triggered by the human papilloma virus (HPV), according to new US research.
Although the research, published in journal Annals of Oncology, shows that risk remains low, with only 0.7 per cent of all men to ever develop oropharyngeal cancer in their lifetimes.
Among men, the lowest risk group were those who had one or no oral sex partners in their lifetimes, with only 1.5 per cent of them getting an oral HPV infection, which rises to four per cent 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 per cent, rising to 7.4 per cent among those who did not smoke but who had five or more oral sex partners.
The rate of infection was highest, at 15 per cent, among men who smoked and had five or more oral sex partners.
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.
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.
It was found 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, with 1.8 per cent of smokers infected, and 0.5 per cent of non-smokers.
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.
Currently there are no tests that can be used for screening people for oropharyngeal cancer. While incidence remains relatively low it is predicted to overtake cervical cancer by 2020, making screening for at risk patients important, says Dr Amber D'Souza at Johns Hopkins Bloomberg School of Public Health and one of the authors of the study.
"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," Dr D'Souza said.