When a health risk goes viral
The growth of virally caused cancers, particularly among men, shows the importance of immunisation programs that vaccinate both boys and girls.
There’s nothing like a celebrity cancer to generate interest and panic in almost equal measure. When Kylie Minogue revealed she had breast cancer there was a surge in women having check-ups. And so it has been with Michael Douglas and his throat cancer and his revelation that it was related to human papilloma virus (HPV) contracted during oral sex. Should oral sex be stopped immediately? Should boys be immunised with the HPV vaccine? What is a man to do if his sexual career has been devoted to women’s pleasure? Can he be screened?
The list of HPV-related cancers keeps growing: cervical cancer in women, anal cancer in both men and women, but particularly men who have sex with men, mouth and throat (oropharyngeal) cancers and more recently, oesophageal (gullet) cancer.
The idea that viruses either cause cancer or are important risk factors is not new. Before HPV was confirmed as a cancer-causing (oncogenic) virus, the most significant oncogenic virus was hepatitis B, which causes liver cancer, although the AIDS (HIV) and glandular fever (Epstein Barr) viruses also increase the risk of a range of malignancies.
The mechanism of cancer causation is different from virus to virus, but most probably involves DNA or immune system damage in one way or other.
The evidence that HPV is related to oropharyngeal cancers has been growing for years. Two decades ago, the diagnoses of tonsillar, tongue and pharyngeal tumours tended to be in older men who smoked and drank a lot (like Michael Douglas, in fact). The pattern has shifted to younger white men who tend not to have those traditional risk factors.
A recent Canadian study confirmed that the incidence of tonsillar cancer appears to have doubled since the early 1990s, associated with an increase in the presence of HPV in the tumours. Various studies suggest that up to 60% of oropharyngeal tumours are now positive for HPV, although European HPV rates seem lower than in North America.
Another tumour that has been increasing around the world with no good explanation until recently is oesophageal cancer, a nasty, poor-prognosis malignancy. Research from Australia and elsewhere has found HPV in a significant proportion of oesophageal tumours, again mostly in men.
But it’s not all bad news.
The fortunate paradox is that HPV oropharyngeal cancers have a better prognosis and appear easier to treat than non-HPV cancers. The analysis is clouded a little though, because even if a man is infected with HPV it is not necessarily the cause of his cancer.
The jury is out on whether it is worth older men being checked for HPV.
Other lucky findings are that, first, it is largely the most common forms of HPV that are involved, and these are covered by current vaccines. Second, many people infected with oncogenic HPV clear it within a few months.
Prevention at a population level is best done by immunising boys as well as girls. There are good reasons to immunise boys anyway. When rubella (German measles) immunisation for girls was introduced to prevent infection during pregnancy and the associated risk of serious birth abnormalities, it was found to be only partially effective because only half the population was covered. Rubella immunisation only really produced benefits when both sexes were included.
The same is likely to be true of HPV, especially since it is sexually transmitted and both partners share responsibility. That’s part of the reason why Australia became the first country in the world to offer free HPV immunisation to adolescent boys.
The jury is out on whether it is worth older men being checked for HPV infection and immunised if they’re clear. One reason is that after a certain age most sexually active males and females have already acquired HPV, although most will have rid themselves of the virus. So they may already have immunity to it.
And should men be screened for oropharyngeal cancers, say with the equivalent of a pap smear of the tonsils? Well, screening for cancer is hugely controversial. After a lot of angst, cost and unnecessary procedures, most findings turn out to be harmless. Besides, years would be needed to develop reliable tests and verify the risk-benefit equation.
So do we put the hex on oral sex? Many would hope not. If parents have their boys immunised that should cover them reasonably well. And for those who probably have HPV already, just remember that you are having sex with everyone that your partner has ever had sex with.
A sobering thought. Anyone for an oral condom?