Study Finds HPV Transmitted by Oral Sex Can Cause Throat Cancer

stem-cellActually, oral sex doesn’t cause throat cancer, but as two recent studies show, it can be the means of transmitting the human papillomavirus (HPV) – which does cause cancer. Two strains of HPV (16 and 18) cause nearly all cases of cervical cancer, however, it is only recently that scientists discovered that HPV 16 is also responsible for up to a third of the cancers in the oropharynx (the middle part of the throat including the soft palate, base of the tongue and tonsils).

Ironically, or perhaps unusually, it was the outburst of a Hollywood celebrity that brought timely attention to HPV and throat cancer. The famous Michael Douglas famously blamed his throat cancer on the practice of oral sex. The furor was so great, that he retracted his statement. Only now, with two new scientific studies, it seems he got it (more or less) right.

Irony aside, HPV infection can be serious. It is the most common sexually-transmitted infection (STI), passed on (typically) through genital or anal sexual contact. Now, research shows it can also be transmitted through oral-genital contact. In both cases, it can cause cancer.

While quite common, HPV infection is among the most likely infections to escape diagnosis. Many people have no outward symptoms, although some develop genital warts (or warts in the throat). The HPV infection generally goes away of its own accord within 1 to 2 years. However, some strains persist much longer than that and increase the risk of developing cancer. Scientists do not fully understand when and how the viral infection escalates into pre- and full cancer, but the connection is certain and the statistics are clear, especially for cervical cancer.

One of the recent studies of HPV and throat cancer looked at the types of cancer-causing HPV (strains 16 and 18). The researchers followed more than 1700 people, who at the beginning were tested free of HPV. (The test, which is relatively simple, looks for the presence of the antibody E6, which indicates the immune system is fighting an HPV infection.) After ten years, 135 of the participants developed throat cancer, with the other 1599 remaining free of cancer. Of those developing throat cancer, 35 percent tested positive for E6, meaning they had contracted HPV. In almost all cases, the cause was HPV-16. It was also significant that among those without cancer, less than 1% tested positive for HPV.

The bad news is that oropharyngeal cancer is increasing. Over the past twenty years, its occurrence has been especially increasing among men and scientists believe that by 2020 HPV will cause more throat cancer than cervical cancer, at least in the United States. Cervical cancer is one of the most common and lethal of cancers for women worldwide.

The somewhat better news is that like cervical cancer, the HPV virus that causes throat cancer may be thwarted by vaccination. The second study of HPV caused throat cancer, a clinical trial conducted in Costa Rica, looked at the effects of HPV vaccine (in this case, Cervarix) on 5,840 women, comparing them to a control group of 1,626 women who did not receive the vaccine. Although Cervarix was developed and is used against cervical cancer (obvious by the name), the study found that only one of the women receiving the vaccine developed an oral HPV infection, compared to 15 of the women who did not have the vaccine.

This clinical trial is, at best, preliminary. Its findings are constrained by sample, location and the conditions of the trial. However, it seems to the medical community that the effect of vaccines for HPV will likely cover both cervical and throat cancer. How much this is so, will depend on further trials. However, as it now seems likely that young boys could also benefit from having the vaccine, there will be considerable incentive for pharmaceutical companies to proceed with definitive Phase III clinical trials in order to get FDA approval for use against oropharyngeal cancer.

Presently there are two FDA approved vaccines for HPV – Cervarix and Gardasil. The manufacturers market both as necessary and routine vaccines for girls; however, they have run into well-documented opposition and considerable lack of acceptance. It goes almost without saying that any sexually transmitted disease involves moral and religious feelings. The idea of inoculating children (now of both sexes) for potentially “immoral” behavior, does not sit well with some people.

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