• 2/28/2004
  • Baltimore, Maryland
  • Michael Day
  • New Scientist Print Edition

Oral sex can lead to oral tumours. That is the conclusion of researchers who have proved what has long been suspected, that the human papilloma virus can cause oral cancers.

The risk, thankfully, is tiny. Only around 1 in 10,000 people develop oral tumours each year, and most cases are probably caused by two other popular recreational pursuits: smoking and drinking. The researchers are not recommending any changes in behaviour.

The human papilloma virus (HPV), an extremely common sexually transmitted infection, has long been known to cause cervical cancers. Several small studies have suggested it also plays a role in other cancers, including oral and anal cancers.

“There has been tremendous interest for years on whether it has a role in other cancers. Many people were sceptical,” says Raphael Viscidi, a virologist at Johns Hopkins University School of Medicine in Baltimore, Maryland, a member of the team that did the latest work.

The researchers, working for the International Agency for Research on Cancer in Lyon, France, compared 1670 patients who had oral cancer with 1732 healthy volunteers. The participants lived in Europe, Canada, Australia, Cuba and Sudan. HPV16, the strain seen most commonly in cervical cancer, was found in most of the oral cancers too.

Antibodies against HPV

The people with oral cancers containing the HPV16 strain were three times as likely to report having had oral sex as those whose tumour did not contain HPV16. There was no difference between men and women in terms of how likely the virus was to be present in the cancers. The researchers think both cunnilingus and fellatio can infect people’s mouths.

Patients with mouth cancer were also three times as likely to have antibodies against HPV as the healthy controls. For cancers of the back of the mouth, the link was even stronger.

The results prove the connection between HPV and oral cancer beyond any reasonable doubt, Viscidi says. “This is a major study in terms of its size,” he says. “I think this will convince people.”

Cancer specialist Newell Johnson of King’s College London agrees. “We have known for some time that there is a small but significant group of people with oral cancer whose disease cannot be blamed on decades of smoking and drinking, because they’re too young,” he says.

“In this group there must be another factor, and HPV and oral sex seems to be one likely explanation. This study provides the strongest evidence yet that this is the case.”

Cancer-causing strains

Genital HPV infections are common. At any one time, around a third of 25-year-old women in the US are infected. It is thought that only 10 per cent of infections involve cancer-causing strains, and that 95 per cent of women will get rid of the infection within a year. But even this does not explain why so few develop cancer.

The latest findings could improve treatments of oral cancers. Many scientists think that HPV infection must persist for tumours to grow, so giving antiviral drugs to people with oral cancers caused by the virus could improve their chances of recovery.

Prevention could soon be a possibility as well. Several research groups are developing vaccines against HPV, intended to reduce the 250,000 deaths worldwide each year due to cervical cancer. It is thought the vaccines would prevent oral infections as well as genital infections.