Increasing evidence suggests that HPV infection of the mouth and throat, presumably acquired through oral-genital contact with an infected partner, can lead to squamous cell cancers of the tongue and tonsils.You know what HPV is, right? Human Papilloma Virus. The same virus that can cause cervical cancer in women and anal cancers in both men and women.
Scientists have been suspecting for years that this virus might be responsible for squamous cell cancers of the oral cavity. Turns out that it is, though it may be a more recent phenomenon related to the increasingly widespread nature of HPV infection.
What is the Evidence?
1. The incidence of certain oral cancers is rising
Doctors and dentists are seeing increasing numbers of tonsillar and tongue cancers in young men and women, even as rates of other oral cancers and the use of tobacco, a factor typically associated with increased risk of oral cancer, have declined, and rates of oral sex have increased.
Confounding factors may be an increase in binge drinking, another risk factor for oral cancer, and the fact that tonsillectomies are no longer regularly performed. But upwards of one quarter of individuals with oral cancer these days do not have a history of drinking or smoking, suggesting that another risk factor is emerging. That factor appears to be HPV.
2. HPV DNA is found in oral cancer cells
Somewhere between 40 and 75% of tongue and tonsillar cancers contain HPV16 DNA. HPV 16 is the HPV genotype most frequently found in cervical and anal cancers, and is known to be sexually transmitted.
Scientists testing tumor samples from Sweden’s tumor registry in 2007 found that the rate of HPV DNA presence in tonsillar cancers increased from 23% in 1975 to 68% in 2002.
3. The risk for oral cancer increases with number of oral sex partners
Having more than 6 lifetime oral sex partners is associated with a greater than threefold increase in oral cancer risk. (NEJM) This risk appears independent of the risk imparted by smoking and alcohol, which is associated with HPV-negative cancers. Again, this suggests that there are separate pathways to oral cancer, one mediated by HPV and the other via some other factor modified that is by alcohol and nicotine.
What is Your Risk for Getting Oral Cancer?
It’s really, really low. According to the SEER database, the the annual incidence of oral cancer is about 10 per 100,000 annually (6 per 100,000 for women and 16 per 100,000 for men.)
So extrapolating from the research, having had oral sex with more than 6 partners would raise the annual risk of oral cancer in a male to 48 per 100,000.
Of course, that’s just the annual risk. The lifetime risk of getting oral cancer is considerably higher, about 1%, give or take, depending upon how old you live to be.
So, if these numbers hold for HPV related cancers as well, and you have more than 6 oral sex partners, your lifetime risk for oral cancer by age 70 will be about 3 %. Which looks like this –
But, the risk of dying from oral cancer is much, much lower, about 2.5 per 100,000 annually, and ranges from 1.3 per 100,000 in individuals under age 65 to about 12 per 100,000 in those age 65 and older. Since HPV cancers are less aggressive than other oral cancers, I don’t think we can extrapolate historic mortality data, so I won’t. But I would suspect that the risk of dying from an HPV-related oral cancer is even lower than the numbers I just quoted.
(This is rough math, and probably not statistically proper, but it’s the best I can do with the data I have. Others who are better at statistics, please feel free to comment and correct this estimate and I will revise if need be.)
By comparison, the annual incidence of cervical cancer in women is about 7 per 100,000 and the mortality about 2.5 per 100,000. The lifetime risk is about half that of oral cancer in males, due, I suspect, to Pap smear screening in women.
Are There Other Risk Factors?
HPV is only one risk factor for oral cancer, though given the advent of the HPV vaccine, it is sure to be the one that gets the most press.
Smoking, excessive alcohol intake and poor dental care are also very important risk factors, as is a diet low in fruits and vegetables. In one study in Poland, 56% of oral cancers could be attributed to smoking, 31% to excessive drinking, 47% to poor dental hygiene and dental care, and low fruit intake to 12%.
These other risk factors appear to be independent of HPV infection in causing oral cancers, and scientists hypothesize two separate paths to oral cancer, one driven by HPV and the other by these other risk factors. Supporting this idea is the fact that HPV-related oral cancers tend to be less aggressive and have better prognosis than those without HPV. In addition, tobacco and alcohol appear to be synergistic in promoting cancers that are negative for HPV, but not in cancers that test positive for the vurus, again suggesting separate mechanisms for malignant transformation.
What Can You Do Now to Prevent Oral Cancer?
1. Don’t smoke
2. Drink to moderation
3. Brush your teeth and see your dentist regularly.
4. Add fruits and vegetables to your diet.
5. Limit your number of oral sexual partners
Will HPV vaccination be added to that list? I expect it will be. The vaccine prevents HPV 16, the subtype most often found in oral cancers.
Merck, the manufacturer of the vaccine, is conducting clinical trials of their HPV vaccine in young men. I would anticipate a “Tell someone” campaign about oral cancers directed at this population sometime in the near future. Time will tell, and only Merck’s marketing department knows for sure.
In the meantime, be careful out there, okay? Oral sex is a very intimate activity. Why not reserve it for those you love? That would limit your partners quite nicely.