Oral sex 'ups' the risk of throat cancer

May 14 2007

According to scientists in the U.S. a virus contracted through oral sex is the cause of some throat cancers.

The scientists at Johns Hopkins University say human papillomavirus (HPV) infection presents a much greater risk factor than tobacco or alcohol use, for oropharyngeal cancers; they say having multiple oral sex partners tops the list of sex practices that boosts the risk of HPV-linked cancer, regardless of tobacco or alcohol use.

In a study of 300 people the researchers found the risk was almost nine times higher for people who reported oral sex with more than six partners.

It is already recognised that HPV infection is the cause of the majority of cervical cancers, and 80% of sexually active women can expect to have an HPV infection at some point in their lives.

For the study the scientists took blood and saliva from 100 men and women newly diagnosed with oropharyngeal cancer which affects the throat, tonsils and back of the tongue and also asked questions regarding sexual practices and other risk factors for the disease, such as family history.

They found that those who had evidence of prior oral HPV infection had a 32-fold increased risk of throat cancer and HPV16, one of the most common cancer-causing strains of the virus, was present in the tumours of 72% of cancer patients in the study.

Study author Dr Gypsyamber D'Souza, says it is important for health care providers to understand that people without the traditional risk factors of tobacco and alcohol use may nevertheless be at risk of oropharyngeal cancer.

The researchers say the virus itself appears to be driving the risk of the cancer up.

Although oral sex was found to be the main mode of transmission of HPV the researchers say mouth-to-mouth transmission, for example through kissing, could not be ruled out.

Experts say while the majority of HPV infections clear up with little or no symptoms, a small percentage of people who acquire high-risk strains may develop a cancer.

They say people should be reassured that oropharyngeal cancer is relatively uncommon and the overwhelming majority of people with an oral HPV infection probably will not get throat cancer.

A vaccine which protects against cervical cancer caused by HPV strains 6, 11, 16 and 18, and also against genital warts is now available and the researchers say the study provides a rationale for vaccinating both girls and boys.

But it is unclear at present whether this vaccine offers protect against oral HPV infection.

The study is published in the New England Journal of Medicine.