Breakthrough research has offered a clue as to why oral cancer has been on the rise recently and more so in persons not regarded as primary-risk candidates. American scientists say that oral sex is a risky sexual act that passes on the human papillomavirus or HPV between partners and may give cause to oral cancer even if the person does not smoke, drink or use any substance known to predispose to the disease.
Says lead researcher Maura L. Gillison, an assistant professor of oncology and epidemiology at the Johns Hopkins Medical Institutions in Baltimore:"There's been a kind of sea change in the last 10 years in who we're seeing with these cancers. It makes sense with some changes we've seen in sexual behavior."
The study, involving 100 people with throat cancer and 200 without it, found that those infected with the human papillomavirus were 32 times as likely to develop one form of oral cancer than those free of the virus.
Patients whose blood or saliva samples indicated that they had prior HPV infection were 32 times more likely to develop oropharnygeal cancer, which affects the throat, tonsils and back of the tongue.
Also, those people who had had more than six oral sex partners were 8,6 times more likely to develop the HPV-linked cancer.
These figures establish HPV infection as the greatest risk factor for this type of cancer, overturning previous theories blaming a pack-a-day smoking habit for 20 years, or regular heavy alcohol consumption over 15 years.
Although previous research had indicated HPV caused oral cancer, this new study appears to be the first to definitively establish the link.
Says Gilson: "It makes it absolutely clear that oral HPV infection is a risk factor".
The study published in the New England Journal of Medicine also provides new evidence that contradicts widespread misconceptions about oral sex.
"Many adolescents, and adults too, say they engage in oral sex as a less risky type of sex," says Mark A. Schuster of Rand Corp. and UCLA. He notes that herpes, syphilis, gonorrhea, HIV and other sexually transmitted infections can be spread through oral sex. "What this article and others show is that you absolutely can get serious sexually transmitted diseases through oral sex."
HPV can be found in saliva, semen and urine, but has a particular affinity for the mucosal skin cells of the penis and vagina.
Oral cancers linked to HPV have been on the rise in the United States since 1973, a trend that may be driven in part by the popularity of oral sex among American teens, according to the authors.
In the light of the increasing incidence of the cancer, authorities should consider programs to vaccinate boys as well as girls against some of the most dangerous strains of HPV, the authors opine.
Proponents of Gardasil, the Merck vaccine drug recommended for young teenage girls against cervical cancer (caused by HPV) could not be in a firmer position. Experts expect the vaccine to be pushed for boys as well, to help cut the risks of developing oral cancer through oral sex.