SINGAPORE - Last week, it seemed that Hollywood actor Michael Douglas was claiming that his throat cancer (diagnosed in 2010) was due to HPV .
HPV, or human papillomavirus, is one of the most common sexually transmitted infections and often linked to cervical cancer.
This is despite the fact that Douglas was a long-term smoker before his diagnosis and has been treated for alcohol addiction.
He then added the dubious claim, possibly an attempt at a joke, that oral sex is also the best cure.
He then proceeded to add: "And if you have it, (oral sex) is also the best cure for it."
His comments led to uproar online, with many questioning his statement.
Even the actor's spokesman had to come out to subsequently deny that Douglas was claiming that oral sex was the cause of his cancer.
He said the actor had discussed the link between oral cancers and oral sex, among other risk factors, but was not referring to his own specific case.
To find out more, we asked ear, nose and throat specialist Dr Mark Khoo, a senior consultant at Mount Elizabeth Novena Specialist Centre to explain.
What is HPV?
Dr Khoo: HPV is a virus that has been known about for a long time.
But we now know that in addition to causing warts on the skin, it can also give rise to warts on mucosal surfaces (areas located inside the body) such as the vagina, vulva, anus, penis, oral cavity and oropharynx (upper part of the throat).
There are around 150 strains of HPV. While most cause warts, only a few cause cancer, namely HPV strains 16 and 18.
How does HPV work?
Dr Khoo: The virus works by taking up residence in the body's cells. It inserts some of its own genetic material (its DNA) into the human DNA. DNA produces proteins that drive cell production.
By inserting its own DNA, the virus gets the human cell to produce viral proteins.
Some of these proteins are harmless, but some cause warts. Some could lead to mutations that cause cancer.
How common is HPV?
Dr Khoo: Very common in Western countries. (The US Centers for Disease Control and Prevention says that approximately 79 million Americans are currently infected, with about 14 million becoming infected each year).
HPV is probably as common in Singapore as anywhere else. But this is only with regards to skin warts and cervical cancer - all our cases of cervical cancer are thought to be due to HPV and sex.
In Asia, the HPV effect is less pronounced in the throat, but this may change.
Is HPV a prevalent cause of throat cancer?
Dr Khoo: Throat cancer is mainly caused by smoking and drinking. Conventional data suggests that 75 per cent of throat cancer victims smoke and/or drink.
It's in the 25 per cent that don't smoke or drink that we are searching for a cause. It is also in this 25 per cent that HPV may be a factor.
It does not help that most smokers also drink. Alcohol is mainly a "promoter". Moderate alcohol consumption probably is not an independent cancer-causing agent, but it can work to promote the cancer causing effect of smoking.
Heavy alcohol consumption, however, is cancer-causing, even without smoking.
HPV's role is thought to be a bit like that of alcohol - a "promoter".
Obviously, in the completely non-smoking, non-drinking group, some throat cancers are caused by HPV alone.
Is it possible Michael Douglas got throat cancer from oral sex?
Dr Khoo: It's hard to give a professional opinion without having access to all his medical information. But my instinct (informed by the above information) is that his cancer is mainly due to his smoking and drinking, with a possibly enhanced risk due to the promoter effect of HPV.
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