Although the majority of cancers are associated with our lifestyle, some tumors have viral origins. In addition to being responsible for cancer of the cervix, the human papilloma virus (HPV) can also infect the cells of the throat and cause cancer of the oropharynx. A look at a cancer of viral origin that is little known, but whose incidence is on the rise.
The human papilloma virus (HPV) is responsible for 5% of all cancers diagnosed each year worldwide. Sexually transmitted, this virus can infect and cause cancer of the genital organs (penis, vulva, vagina), but it is the cervix that remains the preferred site of infection of the virus and most commonly associated with the development of Cancer. Several dozen different HPVs exist, the most dangerous being the HPV 16 and HPV 18 variants which are responsible for the vast majority of all cervical cancers.
Most women will be infected with one or more of these viruses during their lifetime, but the immune system will in most cases be able to neutralize them and prevent the development of cancer. When this defense fails, however, the virus produces two proteins (called E6 and E7) that suppress the function of important tumor suppressors (p53 and Rb) and cause cells to proliferate unchecked. A preventive approach therefore remains the key to combating this cancer, and screening for cervical cancer through tests, followed by a colposcopy or a biopsy for patients with precancerous lesions, has made it possible to reduce the incidence of this cancer considerably in recent years, particularly in the West.
70% of throat cancers are caused by the HPV virus
The fight against HPV is far from won, however, as the significant drop in cervical cancers has been offset by a worrying increase in certain head and neck cancers caused by this virus. For example, cancer of the oropharynx, which affects the portion of the throat behind the mouth, including the base of the tongue, soft palate and tonsils, is 15 times more common in people who are infected with HPV.
Historically, this cancer was a consequence of tobacco, excessive alcohol consumption or a combination of these two factors, but with the decrease in smoking that has occurred in recent years, it is the HPV infection which is now the main risk factor for oropharyngeal cancer. It is estimated that more than 70% of current cases of these cancers are caused by this virus, a proportion that could even reach 90% in the coming decades. If the trend continues, specialists even predict that the number of oropharyngeal cancers caused by HPV will surpass cervical cancers by 2020.
Transmission through oral-genital intercourse with many partners
The increased incidence of oropharyngeal cancer caused by HPV is probably a consequence of changes in sexual practices, since it is strongly associated with the practice of oral-genital contact with a large number of partners. In this sense, recent studies indicate that in the United States, 7% of American adolescents and adults already have the virus present in their mouths and could at the same time allow its transmission during these reports.
Prevention remaining the only effective weapon against this type of cancer caused by a sexually transmitted virus, it is better to limit the number of partners as much as possible and to use a condom during intercourse remain the best ways to reduce the probability of contracting HPV or to pass it on to his partner.
Chaturvedi AK et al. Human papillomavirus and rising oropharyngeal cancer incidence in the United States. J Clin Oncol. 29: 4294-301.
Gillison ML et al. Prevalence of oral HPV infection in the United States. JAMAS; 307: 693-703.