I'm afraid that we're moving right on to another very serious topic. I'd like to discuss awareness of oral cancer, modern screening methods, and the relationship of HPV- human papilloma virus- to cancer in the mouth.
Let's first go back to the late 80's, when I was a resident at Albert Einstein Medical Center in Philly. Yes, yes, the late 80's were lots of fun, but my purpose here is to explain how we thought about risk factors for oral cancer. The overwhelming risk factors were thought to be smoking and drinking. "Sminkers" were thus at highest risk. You know, people who both smoke heavily and drink to excess- "sminkers". Tough guys who ride Harleys without a helmet and strip wire with their teeth, guys with a pack of unfiltered Camels rolled up in their sleeve and a great big anchor tattooed on their arm. Guys who smoke four packs a day, for gosh sakes.
Those weren't the only folks who developed oral cancer, but such was our mental image of the classic patient. And in reality, we weren't profiling excessively. 75% of patients with this disease did share these risk factors, and about 25% of oral cancer patients had no apparent contributing causes that we could identify.
Now, except for the tattoos perhaps, the demographic is changing drastically.
What has changed is the rapid spread of human papilloma virus, HPV from here on. This virus is one causative factor in cancer in the mouth. Recent data confirms that HPV-related oral cancer is now the fastest growing segment of the oral cancer population in patients under the age of 50 years who do not possess the smoking and heavy drinking risk factors.
There are more than 120 strains of HPV, many of which are probably harmless. HPV-16 and HPV-18, though, are implicated in oral cancer formation. In fact, more than 90% of HPV-positive oral cancers are HPV-16-positive. And, here's the kicker- HPV-16 is the same agent that is the cause of more than 95% of cervical cancers in women. It is even found that the proportion of HPV-16-related tonsil tumors has risen from 28% in the 1970's to 68% in the 2000's, which suggests an absolutely dominant role of HPV in oropharyngeal cancers.
Now, liberal as I often am, at heart I'm a rather Victorian sort of fellow in some ways, so touching on this delicate subject is a bit challenging for me, but here goes- the changes in sexual behaviors of young adults over the last few decades are increasing the spread of the cancer-causing versions of HPV. For centuries, HPV has been one of the most common of sexually transmitted diseases in the world. (Because it affects men far less than women, who may develop cervical cancer, and because cancer formation is so far removed in time from the sexual contact, this disease has received far less attention than, say, syphillis, gonorrhea or HIV. We human beings are never very good at risk assessment when the consequences are only linked to the causes over the span of many years.) The fact that oral sex, which is viewed by many as a sort of not-sex, and which perhaps exposes young people to more partners than they would have encountered otherwise, has become so much more prevalent means that this virus has been able to become more virulent. In other words, HPV can afford to cause more cancer, more human disease, both in the cervix and in the mouth- and so it just does.
It is a well established principle in evolutionary biology that a disease-causing agent will make its victim just as sick as it can and yet still be able to reproduce more copies of itself. From http://www.euvolution.com/articles/disease.html :
For agents of disease that are spread directly from person to person, low virulence tends to be beneficial, as it allows the host to remain active and in contact with other potential hosts. But some diseases, like malaria, are transmitted just as well--or better--by the incapacitated. For such pathogens, which usually rely on intermediate vectors like mosquitoes, high virulence can give a selective advantage. This principle has direct implications for infection control in hospitals, where health care workers' hands can be vectors that lead to selection for more virulent strains.
Since cancers take a relatively long time to form, from the virus' standpoint HPV can readily afford to kill us- it will have long since been passed on to many other people by its host. So- it kills simply because it can get away with it.
The cold facts:
-CDC estimates that 5.5 million new genital HPV cases occur each year in the U.S.
-CDC estimates that 24 million people in the U.S. are infected with HPV at any given time. That's about 8%.
-In the U.S., nearly 3 out of 4 people between the age of 15 and 49 years have been infected with genital HPV in their lifetimes.
-Again in the U.S., 34,000 new oral cancer cases are diagnosed each year.
-More than 8,000 Americans will die of oral cancer each year. That's one person per hour, 24 hours a day, 365 days per year. Death takes no vacations.
-Early detection means a far better chance of successful treatment.
We use the Identifi 3000 device to screen for oral cancer. It uses three different wavelengths of light to look for lesions and it is said that this gives up to a year's lead time over what the eye alone can see.
Still, prevention is the most important thing to consider and do some serious pondering on. Armed with this knowledge, each person must make their own decisions as to what behaviors constitute an acceptable risk. But it is a shame to think of condom use preventing the spread of most STD's, including HIV, only to face an entirely different enemy in the form of HPV and the oral and cervical cancers that it contributes to.
Finally, here is the enemy rendered graphically:
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