Consideration should be given to routinely vaccinating young boys against a sexually-transmitted virus linked to mouth cancer, a leading expert says.
Increasing evidence suggests certain strains of the Human Papilloma Virus (HPV) are behind big increases in rates of oral cancer.
In the past 20 years there has been a 200% increase in the incidence of oral cancers in the US associated with HPV. Similar trends have been seen in other parts of the world, including the UK, Scandinavia and Australia.
Part of the reason is thought to be changes in sexual behaviour - especially a more casual attitude towards oral sex.
US cancer specialist Professor Maura Gillison believes the time has come to think about protecting pre-adolescent boys against oral cancer as they become sexually active.
The well-known link between HPV and cervical cancer has led to the routine vaccination of girls aged 12 to 13 in the UK since 2008.
Some have also advocated boys being vaccinated to stem the spread of the virus and prevent genital warts and anal cancers, which are also thought to be caused by HPV.
Prof Gillison, from Ohio State University in Columbus, acknowledged that the idea of vaccinating children to prevent an infection associated with oral sex was "very, very controversial".
But asked if boys should be considered for vaccination, she said: "Yes certainly, I think there's evidence that vaccination of boys, if the vaccine uptake of girls is relatively low, would help not only the boys in prevention of genital warts and anal cancer but also help protect women against cervical cancer.
"The time has come to have a more thorough discussion about the benefits of HPV vaccination for boys - which would include prevention of genital warts and anogenital cancers in boys and girls, as well as potential prevention of oral cancers that are rising in incidence among the young."
She said she told her patients, when asked, to go ahead and vaccinate their sons.
"The vaccine will protect them against genital warts and anal cancer and also as a potential byproduct of that it may protect them against oral cancer caused by HPV," she added.
Some of the most compelling recent evidence had come from Sweden, said Prof Gillison, speaking at the American Association for the Advancement of Science's annual meeting in Washington DC.
Research there had shown that since the 1970s the proportion of HPV-positive tonsil cancers had risen from a quarter in the 1970s to 90% by the mid-2000s.
The HPV strain mostly linked to cervical cancer, HPV 16, was even more closely associated with oral cancers, said Prof Gillison.
While it was responsible for about 60% of cervical cancers, it was present in up to 95% of cases of HPV-positive oral cancer.
Someone exposed to HPV 16 had an estimated 14-fold increased risk of developing cancer of the mouth or upper throat.
Prof Gillison added: "When we look at cancer incidence rates in the US, what really is driving the increase in oral cancers related to HPV is the year in which you are born.
"It really is the group of individuals who were born after 1935 who have really started to see this increase.
"Every birth cohort appears to be at greater risk from HPV and oral cancers than the group born before them. These were people who were in their teens and 20s in the 1950s and 1960s when the sexual revolution happened in the US.
"What really drives these cohort effects is societal changes that tend to affect younger people first."
She added that the number of sexual partners someone had in their lifetime - particularly the number on whom they had performed oral sex - was strongly linked to oral HPV infections.
"The higher the number of partners that you've had, the greater the odds that you'd have an oral infection," she said.
Sara Hiom, director of health information at Cancer Research UK, said: "Cancers in the mouth and throat are on the increase and rates have been rising dramatically in the UK since the mid 1980s, especially in people in their 40s, 50s and 60s. The proportion of these cancers that appear to be related to infection by the human papilloma virus (HPV) is also increasing.
"But while it's reasonable to assume that HPV vaccination in girls and boys would protect against these cancers, there is as yet no evidence as to whether the current HPV vaccines are effective at preventing them.
"The trials done to date have looked at cervical cancer or genital warts as endpoints, so we need new studies to show effectiveness against these HPV-related head and neck cancers.
"Yet most oral cancers diagnosed in people over 50 in the UK are still related to tobacco and alcohol use."Reuse content