A rapidly expanding subset of head and neck cancers are acquired through human papilloma virus (HPV). This virus has been identified as a human carcinogen for six types of cancers, including cervix, penis, vulva, vagina, anus and oropharynx.
There are many subtypes of HPV. However, epidemiologic and molecular studies have identified the HPV-16 genotype as the main causative agent. The oropharynx is a region of the throat that contains a number of structures, including the base of the tongue and the tonsils. It is now estimated about 70 per cent of all cancers of the oropharynx are caused by HPV; this has been deemed an epidemic of our time.
By 2020, the annual number of cases of HPV-related oropharyngeal disease is projected to outnumber the cases of HPV-mediated cervical cancer.
In the US, 78 per cent of HPV-associated cancers in men are oropharyngeal cancers. As a result, it is important to consider ways to expand our HPV prevention efforts to boys and men.
Other high-risk HPV genotypes such as HPV-18, 31 or 33 are also causative, but are less common. HPV causes throat cancer in much the same ways as it causes cancer in the cervix. The virus’s DNA uses healthy human cells to produce two harmful proteins called E6 and E7. These bind to and shut down, two important tumour-suppressor proteins.
Up to 90 per cent of patients with HPV oropharyngeal cancer present with an asymptomatic neck lump. Sometimes the primary tumour site in the tonsil or base of tongue is not visible because these tumours are often small and concealed within abundant surrounding tonsillar tissue.
At time of treatment, these patients tend to be about 10 years younger when compared to HPV negative patients, many in their late 40s or early 50s. This difference in patient age has major implications in terms of the ability to tolerate treatment, which can affect the prognosis.
Treatment can include surgery, radiation therapy and/or chemotherapy. HPV- positive oropharyngeal cancers have a significantly better response to treatment because overall there are fewer mutations within the tumours.
Vaccination
The HPV vaccine has attracted considerable negative attention in recent months regarding vaccine safety and efficacy, distrust of pharmaceutical companies and government and a belief that school-age children are too young for HPV vaccination.
Since first being licensed at the beginning of 2006, more than 200 million doses of the vaccine have been distributed around the world. It has has been repeatedly investigated and scrutinised and studies consistently report a highly effective vaccine with an excellent safety profile.
No vaccine or drug is 100 per cent safe. Concerns about the vaccine fall into four main categories, chronic fatigue, complex regional pain syndrome and postural orthostatic tachycardia syndrome and autoimmune disease. Millions of girls have been investigated but studies consistently report there is no evidence these syndromes are associated with HPV vaccination. The numbers of patients presenting with these disorders is similar in vaccinated and non-vaccinated populations.
The vaccine does cause some side effects but the most common adverse events reported were considered mild. These findings are similar to the safety reviews of two other teenage vaccines – meningococcal vaccines and tetanus booster vaccines. For serious adverse events reported, there has been no unusual pattern or clustering that would suggest that the events were caused by the HPV vaccine.
These are the findings of articles published in the Lancet, Lancet Oncology, Lancet Infectious Diseases and the New England Journal of Medicine.
An aggressive stance on HPV immunisation and screening is needed to prevent the loss of countless lives from cancers that are largely preventable.
Vaccinating girls and boys will lead to decreased HPV transmission rates and increased herd immunity, and will prevent not only cervical cancers but also other HPV-associated malignancies in both women and men.
This has been the experience in Australia and other countries leading the fight against HPV cancer. The HSE has established an excellent vaccination programme for young girls. Vaccination of both boys and girls is now required immediately so that that the full benefits of the vaccination programme can be realised. James Paul O'Neill is a professor of otolaryngology, head and neck surgery, at the Royal College of Surgeons in Ireland.
