Sexual Studies: Does Oral Sex Really Cause Cancer? Let’s take a closer look.

Every Saturday The CSPH highlights news or recent research in the field of human sexuality. This week we’re looking at a large review study from the most recent issue of the Journal of Sexual Medicine that seeks to answer the question of whether oral sex causes head and neck cancer.

Traditionally, these cancers are observed in the 60+ set.  However, recently, there has been an increase in head and neck cancers, specifically of a type called oral squamous cell carcinomas (OSCCs), among younger individuals that has led the media, epidemiologists, and oncologists to ask: what’s going on?

The theory goes that human papillomavirus (HPV), which is best known for its necessary-but-not-sufficient causal link to cervical cancer, is also responsible for this shift in OSCC diagnoses in younger individuals.  But before we go into that, it is important to explore HPV in more depth:  there are many different strains of HPV, some of which cause disease and others that are completely benign.  HPV infections from some strains are fairly common in adolescents, women in their early 20s, and women who’ve gone through menopause, but HPV-related diseases tends to stay rather low since the body does a relatively good job at clearing the infections on its own.  While the mechanisms behind this are not fully known, the authors provide additional in-depth discussion of this background information.

Since the release of the HPV vaccine, a lot of information regarding its relationship to various cancers has gotten a bit exaggerated.  The number of new OSCCs diagnosed each year has actually decreased in recent years and it is more the shift in demographics of the cancer that have raised concern.  So what did the authors find?  Is HPV really causing this shift?

Not completely.  OSCCs are associated with HPV in that patients with this disease tend to be HPV-positive and have the same strain of HPV (16) implicated in cervical cancer; however, there is a large, and growing, body of evidence telling us that this is not the whole story.  As mentioned above, HPV naturally “waxes and wanes” throughout the lifecycle of an individual.  Additionally, the human body is fairly capable of removing the virus on its own, and there is a poor correlation between oral and genital strains within individuals and between couples.  This last piece of evidence is certainly the strongest reminder that our basic question—does oral sex cause cancer?—is far more complex than we imagined.

In fact, the story does not stop at these natural factors: prolonged marijuana use (20 years or more) has recently been implicated in the causal pathway of OSCCs for individuals who are 55 years of age and younger.  The research suggests this may be because some aspect of marijuana interferes with the body’s natural ability to clear carcinogenic HPV-infections, which, in turn, allows the infection to develop into cancer.  Tobacco use, alcohol intake, poor oral hygiene, lifetime number of sexual partners and oral sex partners, oral-anal contact, and being immunocompromised also have been cited as playing a role in increasing one’s risk for OSCCs.

Overall, this review is a bit of a disappointment.  While very few diseases exist where there is a direct causal pathway (e.g. doing A causes disease B), the review does not add much to the conversation around this topic.  It basically tells us that we still don’t know if oral sex causes cancer, but that you shouldn’t be worried if you are in a closed sexual system (monogamous relationship in which neither partner has other partners) and no immuno-compromising factors (e.g. immunosuppressent drugs, HIV/AIDs, etc) are present.  And if you do not fall into this category?  Well, you will do best to follow a “healthy [lifestyle that promotes] good immune functioning coupled with regular medical checkups aimed at early detection and treatment.”  It kind of feels like the authors are leaving you on your own unless you are in a 100% monogamous relationship.

The other issue with this review is that it tells us nothing about how the authors chose the studies they reviewed.  A brief note in the abstract mentions that 196 articles were read but this does nothing to reassure readers that these were quality articles.  In turn, a meta-analysis, where articles are screened out for only the most scientifically-sound methods and results from all studies are analyzed together, would have been a better use of the authors’, and readers’, time because it would actually provide some solid data towards answering the research question.

Finally, it feels at times as if the authors were grasping at straws and writing just to write.
The authors do not write in a manner that convinces readers, one way or the other, regarding the link between oral sex and cancer.The overall tone, the lack of statistics, and the use of terminology such as “negative emotions” distracts from the article’s contribution.  While there is no denying that the connection between oral sex and cancer is, as the authors put it, “more ambiguous, more complex, and more nuanced,” the exploration of this could have been done in a much better and more concrete fashion.

Citation
Rosenquist SE. Is oral sex really a dangerous carcinogen? Let’s take a closer look. J Sex Med 2012;9:2224–2232.

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