The truth about sex and cancer
Actor Michael Douglas does not regret his years of smoking, drinking or recreational drug use. Instead, it is oral sex that has given the 68-year-old father of three cause for concern. The Basic Instinct star said he believes that performing oral sex caused the stage four throat cancer that nearly killed him three years ago.
"Without wanting to get too specific, this particular cancer is caused by HPV [human papillomavirus], which actually comes about from cunnilingus," he told the Guardian.
Although he now denies a direct link, it's still worth looking into the science behind his initial claim.
Douglas, who is married to Catherine Zeta Jones, also said stress hurt his health. His 34-year-old son Cameron, to first wife Diandra, was imprisoned in 2010 for drug possession and dealing.
"I did worry if the stress caused by my son's incarceration didn't help trigger it," said the Oscar winner who was hospitalised for alcohol abuse in 1992. "But yeah, it's a sexually transmitted disease that causes cancer. And if you have it, cunnilingus is also the best cure for it."
Professor Mark Schifter of Sydney University's Faculty of Dentistry says: "There is evidence to suggest that cunnilingus for men can cause oncogenic cancer."
As for Douglas' belief that stress contributed to his cancer, Schifter says: "We know stress has an impact on the immune system to a greater or lesser degree, but it is not as straightforward as 'because I'm stressed, I get cancer'."
He also dismisses Douglas' (serious or joking) assertion that oral sex could help cure it. Apart from pointing out that with the type of intensive treatment a person receives for cancer, "you are not going to be up to doing much". He says: "No, I don't think [it would help]. It would be very hard to get a randomised, controlled study to prove that."
"One retrospective study found that in the 1970s only 22 per cent of those with mouth or throat cancer tested positive for HPV. This figure rose to 93 per cent by 2006.
"Oesphageal cancer has exponentially risen by 600 per cent over the last 40 years," Shan Rajendra, Professor of Medicine at the University of New South Wales, recently told ABC's Radio National. "It's the fastest growing cancer in the Western world."
Rajendra also led a study, published in the April 2013 edition American Journal of Gastroenterology, that adds weight to these findings.
Of the 261 participants, Rajendra and his fellow researchers detected HPV in about 66 per cent of those with oesophageal cancer.
HPV is the most common sexually transmitted infection. So common that "it could be considered a normal part of being a sexually active person", says the Department of Health and Ageing.
About 75 per cent of New Zealanders become infected at some point in their lives, but many do not experience symptoms and it often clears up naturally in about eight to 14 months.
"Ninety-five per cent of us will get rid of the human papillomavirus ," Rajendra said. "It's that five per cent that persists."
The New Zealand government provides a vaccine free to girls aged 12 to 20 years old through an HPV Vaccination Programme.
Professor Schifter says it may be worthwhile considering paying for boys. "Ideally," he says, "you need to be vaccinated before you are sexually active... for those already exposed to the virus the vaccine will not protect you [from HPV]."
Whether or not oral sex or oral sex alone led to Michael Douglas' cancer is debatable, as HPV is still not the biggest risk factor for head and neck cancers. "First and foremost it is still smoking. Secondly it is alcohol and the worst combination is smoking and alcohol," Schifter says. "The number of partners you have is also thought to be a risk as you are exposed to more viruses."
To treat his cancer, which he has been clear of for more than two years now, Douglas endured an eight-week course of chemotherapy and radiation and now has check-ups every six months.
The good news, for those with HPV associated cancer, is "if they don't drink and smoke their survival rate is significantly better - 80 to 90 per cent", Schifter says.