THURSDAY, May 14, 2009 (Health.com) — Human papillomavirus, or HPV, is a sexually transmitted virus that can wreak havoc in the body, causing genital warts and cancers of the cervix, anus, head, or neck, depending on where and what strain of the virus strikes.
Now a new study suggests that this "bad news" virus may actually be good news for people who already have cancers of the upper throat or back of the tongue. People with these types of tumors, known as cancers of the oropharynx, have a better chance of survival if the tumors contain HPV than if they don’t, according to a study released this week that is to be presented at the American Society of Clinical Oncology meeting later this month.
In fact, the difference is so substantial that researchers say that these types of tongue and throat cancers should be studied and treated as if they are two separate types of cancer—one probably caused by HPV and the other caused by other factors, usually prolonged use of cigarettes or alcohol.
The American Cancer Society says that more than 35,000 people in the United States were diagnosed with oral or oropharyngeal cancer in 2008, and more than 7,500 people died of the disease.
In the study, 64% of people with oropharyngeal cancer were found to have HPV-positive tumors, and these patients were about half as likely to die within five years of diagnosis as those with HPV-free tumors. This was true even after the researchers took into account six major factors that can affect survival, including treatment.
"HPV tumor status was found to be markedly associated with overall survival," says lead author Maura Gillison, MD, PhD, professor of medicine, epidemiology, and otolaryngology at Ohio State University in Columbus. At two years, 88% of patients with HPV-positive tumors were alive compared to 66% for HPV-negative tumors.
In the study, the researchers looked at 323 people with oropharyngeal cancer who were treated with a combination of chemotherapy and radiation in the Radiation Therapy Oncology Group clinical trial. About 9% of patients with HPV-positive cancers went on to develop a second type of cancer, compared with 18.5% of patients with HPV-free tumors. (These types of second tumors are common in oropharyngeal cancer survivors.)
"This seems to be a well-conducted study and very insightful analysis," says Douglas Blayney, MD, president-elect at the American Society of Clinical Oncology. "Now we have two kinds of oropharyngeal cancer that we've recognized—HPV-positive and non-HPV-associated cancers."
Dr. Gillison says that HPV-related cancers are on the rise, and the virus is now the number one cause of throat cancer in the United States—more than smoking or alcohol.
"In the U.S., the proportion of the population that smokes has gone down over time; so has the per capita consumption of alcohol. The number of sexual partners has gone up over time," she says. “The patient population that we've seen [in terms of oropharyngeal cancer] has completely changed over the last 10 years. I used to see almost exclusively smokers and drinkers and now it's almost exclusively young patients with HPV-related cancers."
She estimates that HPV causes 20,000 cancers each year, about half of them cervical cancer.
Although new HPV vaccines, such as Gardasil, are aimed at preventing cervical cancer, they may also protect against oral cancers, she says.
"There is reason to be optimistic that the HPV vaccine will prevent oral infections that lead to cancer. Most of the HPV-positive cancers are caused by HPV-16, and the vaccine covers this type," she says. "There's every reason to suspect that it will be effective, but of course that remains to be demonstrated."
In the meantime, HPV testing may help determine what type of treatment should be used for individual oropharyngeal cancer patients.
"I think HPV status determination will be part of standard of care. Patients are starting to demand it because of its prognostic implications," says Dr. Gillison. "It's having a pretty profound impact on how we design clinical trials for head and neck cancer because of the profound difference in survival between the two groups."