After Michael Douglas' claims, the doctors' verdict on oral sex: There's only a 'very small' risk of cancer

Michael Douglas and Catherine Zeta-Jones on 22 April 2013 (Getty Images)

Michael Douglas may have been displaying admirable candour when he told a journalist this weekend that his throat cancer had been caused by a virus “which…comes about from cunnilingus” – but he also sparked a minor health scare.

Cancer specialists have been queuing up to reassure people that, while Mr Douglas is right on some points, the actual risk of getting cancer from oral sex is “very small”.

Asked if cancer had made him regret years of smoking and drinking Mr Douglas said: “No. Because without wanting to get too specific, this particular cancer is caused by HPV [human papillomavirus], which actually comes about from cunnilingus.”

However, Dr James McCaul, a head and neck cancer specialist at Bradford Royal Infirmary said that there was no way Mr Douglas could be sure his cancer was a direct consequence of oral sex.

“The only thing you could say for sure in such a case, is that there was a cancer and HPV virus particles were found,” he told The Independent. “Michael Douglas smoked cigars and drank as well. Without knowing his medical history we can’t say much for certain, but his cancer can’t be attributed solely to oral sex.”

The film star was right in that some HPV infections can lead to cancer, but experts pointed out that tobacco and alcohol use were also serious risk factors.

A very common virus, HPV has 100 variants, 15 of which are linked to higher cancer risks. It can be transferred by intimate contact – anything from open mouth kissing to penetrative sex.

By the age of 25, 90 per cent of sexually active people will have been exposed to HPV of some form, but in the vast majority it is completely harmless.

However, in a small number it can lead to a persistent infection, causing changes in cells that mean they can become cancerous. Around 25 – 30 per cent of throat cancers are believed to be HPV-related.

One American study suggested that the risk of oral HPV infection was higher for men because concentrations of the virus in the female genitalia were higher, making cunnilingus a higher risk activity than fellatio. People who smoke are much less likely to clear the virus from their body.

There has been a significant increase in instances of throat cancer since the mid-1990s, with cases doubling to almost 1,000 annually. Some experts have suggested this could be a legacy of diversifying sexual practices from the 1960s onwards. However, Dr Kat Arney, science information officer at Cancer Research UK, said that it was still uncertain why HPV-related cancers were on the increase.

“We know there’s been a rise in head and neck cancers [of which throat cancer is one] and a rise in the proportion that are down to HPV,” said Dr Arney, “But at the moment there isn’t enough evidence to prove that changing sexual behaviour has led to more transfer of HPV and more head and neck cancers, and more studies need to be done.”

HPV is also linked with 99 per cent of cervical cancers. Girls aged 12 to 13 are offered an HPV vaccination as part of the NHS Childhood Vaccination programme and there are increasing calls for all young people to be vaccinated before they become sexually active.

Another of Mr Douglas’ claims which raised the eyebrows of experts was that “the best cure” for HPV-related cancer was more cunnilingus.

Dr Arney added that there was “no medical evidence that oral sex can treat or cure cancer”.

What the experts say:

Dr Kat Arney, Science Information Officer at Cancer Research UK

“We know that HPV is a risk factor for certain types of oral cancer. There are lots of other risk factors – tobacco and alcohol are two of the main ones. We don’t know anything about Michael Douglas’ medical history, so it’s very difficult to say that it was definitely HPV, that he caught through oral sex, that caused his cancer.

Dr James McCaul, head and neck cancer specialist at Bradford Royal Infirmary

Michael Douglas can’t be 100 per cent confident in saying that his cancer was caused by oral sex. The only thing you could definitely say in such a case is that there was a cancer and HPV virus particles were found. In the UK there’s still more head and neck caused by tobacco usage and alcohol consumption or a combination of the two, than by HPV. Michael Douglas smoked cigars and drank as well, without knowing his medical history we can’t say much for certain, but his cancer can’t be attributed solely to oral sex.

Jason Warriner, Clinical Director at the Terrence Higgins Trust

That he’s said this does raise awareness of sexual health issues and how they can affect anyone, from people who are well known to the person-in-the-street. We should keep this in perspective though so that it doesn’t cause any undue panic or concern. It also raises the issue of vaccination of young people against HPV. We think that all young people should be offered the vaccination before they’re sexually active.