Author: UC Davis Comprehensive Cancer Center
Humanpapilloma virus (HPV) is now the leading cause of certain types of throat cancer. Dr. Michael Moore, director of head and neck surgery at UC Davis and an HPV-related cancer expert, answers some tough questions about the trend and what can be done about it.
Q: What is HPV and how is it related to head and neck cancers?
A: There are about 150 different types of HPV, but HPV 16 is the one that most frequently causes cancers that affect the tissue in the oropharynx, which includes back of the throat, soft palate, tonsils and the back or base of the tongue. You can get non-cancerous lesions from other types of HPV that look like warts in the nose, mouth or throat, called papillomas. Some can develop in childhood just from exposure early in life. Some develop later in life and only occasionally turn into cancer.
Q: How do you get HPV?
A: HPV can spread from mother to her baby around the time of delivery. It also spreads through unprotected vaginal, anal or oral sex, and even open-mouth kissing. Some people have been found to be infected without an obvious cause.
Q: How does HPV cause cancer?
A: Most people who are infected clear the virus on their own. In a small group of people it hangs around and causes a persistent infection. Around 1% of US adults have a persistent HPV 16 infection, and in a small subset of these individuals the DNA of the virus incorporates itself into the DNA of the person infected and can start to make proteins that then predispose that person to developing cancer.
Q: How prevalent are HPV-related throat cancers?
A: Traditionally, the risk factors for head and neck cancers were tobacco and alcohol use, but over the last 20 or 30 years we found the rates of those cancers going down because smoking rates have gone down. Meanwhile, the incidence of head and neck cancers related to HPV has gone up more than 200 percent over this time period. This increase has been so dramatic that HPV-related throat cancer has recently surpassed cervical cancer as the most common HPV-related cancer in the United States.
Q: Why are the rates going up?
A: Unlike with cervical cancer, in which the PAP smear is highly effective at finding potentially cancerous or pre-cancerous cells, there is no good screening test for these head and neck cancers. Currently, the use of swab tests for HPV is effective in finding out if you have an HPV infection, but not in determining if the infection will be persistent or if you will ever develop cancer. As a result, such tests are not endorsed as a way to screen for these tumors.
Q: Do both men and women get thee cancers?
A: Men are four times more likely to be diagnosed with an HPV-related head and neck cancer. Researchers don’t yet know why. It may have to do with sexual practices or related to the types of exposure they receive. The local or systemic immune system may also play a role.
Q: Can HPV-related head and neck cancers be prevented?
A: We have a very effective vaccine against HPV, and we know the vaccine can prevent oral HPV infections. In fact, studies have shown that the vaccine is 93 percent effective in preventing the oral infections that cause head and neck cancers. We recommend two injections for adolescents under age 15 and three for those over 15. The vaccine is recommended for children age 10-11, but vaccination can start in children as young as age 9, and in boys as late as age 21 and in girls as late as 26. It is also important to maintain safe sexual practices and avoid other potentially cancer-causing exposures such as tobacco, alcohol and marijuana.
Q: What are the main barriers to vaccination?
A: Studies have shown that the biggest reason kids don’t get it is lack of physician endorsement or recommendation. The American Cancer Society is trying to change that, asking physicians to introduce it to parents when they discuss other adolescent vaccines. There has also been concern that parents aren’t comfortable talking about sexuality with their children, and some have worried that if the child gets the vaccine they are more likely to be sexually active. That theory has been debunked in scientific studies.
Q: How safe and effective is the HPV vaccine?
A: It has a very safe track record and is continually undergoing evaluation to look for potential side effects. While there are some risks with any vaccine, one of the most common side effects is that patients may feel light headed after being vaccinated, and it is recommended they are observed for 15 minutes afterward.