The HPV vaccine helps prevent cervical cancer. But can it also help prevent mouth and throat cancer? Researchers are working to answer this question now.
We have known for a long time that HPV (human papillomavirus) causes cervical cancer, and we now know that the virus also causes other cancers including oropharyngeal cancer, a type of oral cancer affecting the back of the mouth and throat. In fact, oral cancer is the most common type of cancer caused by HPV infection in Canada, with 1,335 cases in 2012.
Men are more than 4 times more likely than women to get HPV-related mouth and throat cancer. And although the risk of these cancers is increasing for both sexes, it is rising at a much faster rate in men. If these trends continue, we will soon see HPV causing more mouth and throat cancers in men than cervical cancers in women.
HPV vaccine prevents cervical cancer
In 2006, the first HPV vaccine became available in Canada. And just 10 years later, HPV vaccination programs for women have been successful. Although there is usually a long time between HPV infection and cancer development, studies have already shown that these programs have led to fewer women with abnormal cervical tissue changes, which are the first step in cervical cancer development.
HPV vaccines have been well studied for preventing cervical, vaginal, vulvar, penile and anal cancers in men and women. But this research does not tell us for sure if the vaccine will also work against oral HPV infection. We do have some information that shows HPV vaccination prevents oral infection, but we need to know more about whether this means it can prevent mouth and throat cancer.
Link between oral HPV infection and cancer is still unclear
More than 40 types of HPV infect the genital areas of men and women, and these types also infect the lining of the mouth and throat. All HPV vaccines available in Canada protect against HPV types 16 and 18, which are the types that most commonly cause cancer.
Nearly 90% of HPV-related mouth and throat cancers are caused by HPV type 16, while HPV types 18, 33 and 35 can also cause oral cancer. Unfortunately, we don’t know exactly how oral HPV infection leads to cancer.
It is also difficult to know whether a person has an oral HPV infection. Doctors may see some abnormal tissue changes caused by oral HPV infection, but these changes are often found in the back of the mouth and throat and can be difficult to see. This makes it harder to study the relationship between oral HPV infection and oral cancer.
Researchers need to study key questions about HPV vaccine
To fully prove that this vaccine can help prevent mouth and throat cancer, researchers need to answer these questions:
- Do differences between how HPV affects the mouth compared to the cervix and other areas of the body affect how well the vaccine works?
- Will the dose and vaccination schedule being used now to prevent cancers of the cervix, anus or genitals work as well in preventing mouth and throat cancers?
- As more people remain infected with oral HPV at an older age, is a booster vaccine needed later in life?
Research has shown that the HPV vaccine protects against the common types of HPV that cause oral infection, which means it will most likely also prevent mouth and throat cancer though more research is needed to confirm this. We would like to see HPV vaccination programs also lower the number of oral cancer cases in Canada, just as they have for cervical cancer.
Katherine Wright, PhD