A vaccine that prevents cancer is the dream of just about every patient, doctor, and public health official. Therefore, hopes were quite high five years ago, when the U.S. Food and Drug Administration approved a vaccine to prevent human papillomavirus, or HPV, a sexually transmitted virus that causes almost all cases of cervical cancer.
But despite its clear efficacy, the vaccine has been something of a dud. According to a 2008 survey, only 34 percent of the target crowd, girls aged 13 to 17 years, had received it. The reasons for the slow uptake relate to generic vaccine issues (cost, pain, distrust) as well as a particular discomfort with this one, dubbed the "sex vaccine" by many conservatives, who object to it on the grounds that it somehow promotes licentious behavior (as if it were possible to make teenagers any hornier).
However, a new study presented at last week's annual meeting of the American Society of Clinical Oncologists makes the vaccine look even more valuable. Though preliminary and still unpublished, these findings have the potential to finally shift the perception that HPV is a woman's problem and convince parents to get their boys vaccinated against the virus, too.
The researchers make the most compelling case to date that HPV causes yet another malignancy—oropharyngeal cancer, a disease that affects men three times more often than women. (It's a subcategory of "oral" or "head and neck" cancer, which also predominantly affect men.) Their work appears to have settled a debate that had been rattling on for a decade, ever since clinicians first noticed a change in the way oral cancer was behaving.
In the past, oral cancer had been a disease of drinkers and smokers—the poster child was Ulysses S. Grant, who died of the disease (and knew plenty about drinking and smoking). But in the 1990s, more and more cases were seen in nonsmokers, puzzling clinicians; furthermore, the tumors were found in a different area of the mouth—the oropharynx (or front of the mouth), especially the tonsil and the base of the tongue. Previously, oral cancer tumors were mainly seen further back in the throat or near the voice-box.
So began a pursuit that proceeded along two lines of inquiry. First, the epidemiologists who track rates of cancer over time found an alarming rise in cancers of the tonsil and base of the tongue, with a simultaneous decrease in oral cancers found in the other, traditional smoking-related sites. Meanwhile, scientists found that many of the tumors in nonsmokers had HPV in them. Though an intriguing finding, this isn't the same as saying that HPV was causing the cancer. Perhaps HPV had been in oral cancers all along, and no one had thought to look.
So that's exactly what the current investigators did. The researchers, from the National Cancer Institute, examined 271 oropharynx tumor samples collected between 1984 and 2004 using new, super-sensitive molecular detection methods that were not available in the '80s and '90s. Bingo: They found a four-fold increase in HPV-positive tumors over the 20 years. (HPV was in 16 percent of early samples, compared to 73 percent of recent ones.)
In many people's view (including mine), this new study nails HPV as the cause of many oral cancers. At the same time, it makes a mighty persuasive case for boys to get vaccinated against HPV. This is a good thing: If vaccination rates are low for girls, they're invariably lower for boys, who until now had no logical (read: selfish) reason to get the expensive series of shots. (The FDA approved the vaccine for boys in 2009, but wimpily, without any strong recommendation to actually administer it.) OK, sure, it prevents venereal warts, which are no fun. But warts may not seem like such a big deal to a harried mom who has to drag her little darling to the pediatrician three times in six months to ward them off. Now that HPV has been convincingly linked to oral cancer in men, parents have a much more compelling reason to get Junior vaccinated than altruistic concerns about the health of any future female sex partners he may have.
There is one large caveat to this dream of a healthier tomorrow. There are some 20 different HPV strains that can lead to cancer, and while current vaccines prevent the ones that cause 70 percent of all cervical and the majority of oropharyngeal cancers, they're not completely comprehensive. (To make a vaccine effective for all strains of HPV—including the 100 or so that don't cause cancer but may cause warts and other skin problems—you'd need a syringe the size of a milk carton.) So parents should know that getting their sons and daughters these shots won't guarantee that they willnever develop HPV-related cancers.
But even with this limitation, the potential benefit of the vaccine is quite large. Cervical cancer is the most common cause of cancer death in women in many developing countries; in the United States, Pap smears and early treatment have sharply reduced the impact, though it still affects 12,000 women a year and kills 4,000 (PDF). Meanwhile, head and neck cancer is diagnosed in 36,000 people (mostly men), killing 8,000, making it the eighth-most-common cancer for men—a figure that will continue to rise as the impact of HPV infection is manifest. Indeed, the NCI researchers projected that, given the current increase in cases, HPV-related oropharyngeal cancers would be more common than cervical cancer by the year 2020.
If the past is any indication, though, I suspect a more eyebrow-raising angle will overshadow this important public health story. Since the link between HPV and oral cancer was first floated 10 years ago, the media has tended to focus on just one aspect—the possible connection between oral sex and the rise in oropharyngeal cancers. However, there's no definitive evidence yet of a causal relationship between the activity and the disease. That's not to say that people shouldn't exercise a reasonable amount of caution when having oral sex. But when popular opinion (particularly in matters sexual), wags science, no one benefits.
It's easy to see why the notion that oral sex can give you cancer is so attractive. It makes for an irresistibly lurid headline, of course, and it appeals to the secret Victorian hidden less or more deeply in all of us. (Everything fun has a price—everything!) And to be fair, the circumstantial evidence is compelling. It's well understood that HPV is transmitted through other kinds of intimate contact, such as vaginal sex. HPV seems to grow quite well on mucous membranes, those nonskin tissues that line the mouth, nose, vagina, anus, and a few other anatomic areas, and which may touch quite a bit during oral sex.
As an explanation for the uptick in oropharyngeal cancers, though, oral sex has one glaring problem: HPV-positive head and neck cancer is, inexplicably, a guy's disease. If oral sex were driving the issue, wouldn't we see a commensurate rise in HPV-positive tumors among women? Unless the announcement was screened out by my workplace email filter, I don't think anyone has demonstrated that cunnilingus is being practiced more often than fellatio.
Furthermore, many people with HPV-positive head and neck tumors deny having had much oral sex. According to a 2010 review of several studies on the topic, more than half of such patients reported five or fewer lifetime oral sex partners, and 8 to 40 percent said they had never had oral sex.
Finally, the argument that oral sex is driving the rise in these cancers carries the implicit suggestion that oral sex patterns of recent years vary considerably from previous generations. Among the many things we don't know about our forebears, what they did and didn't do in the bedroom surely ranks near the top. And it always is a bad wager to bet against the likelihood that everyone, in every decade, was having all types of sex, and as often as possible.
To be fair, the oral sex angle does make one important contribution to the efforts to control HPV: It gets people's attention. As the titillated masses wait for the truth to emerge, here's hoping they do the right thing—and take their kids to the corner pediatrician to get vaccinated.