The Oral Cancer Foundation
In a new study funded by the National Cancer Institute, Ohio State University and the Oral Cancer Foundation, the forecast for the incidence of posterior of the mouth oral cancers shows that they have been increasing in incidence in recent years, and that trend is going to continue.
These cancers are caused by a virus transmitted during oral sex, researchers reported on Monday in an article published in the Journal of Clinical Oncology.
The virus is the same one that causes many cases of cervical cancer: human papillomavirus (HPV) Type 16. There are about 130 varieties of HPV that are currently known.
Researchers tested tumor samples from 271 patients with certain types of throat cancer diagnosed from 1984 to 2004. The virus was found in only 16 percent of the samples from the 1980s — but in 72 percent of those collected after 2000. The researchers estimated that over all, these oropharyngeal cancers (base of tongue, tonsil and oropharynx) sometimes referred to as throat cancers, caused by the virus have increased to 2.6 per 100,000 people in 2004, from 0.8 cases per 100,000 people in 1988. If the trend continues, by 2020 the virus will be causing more throat cancer than cervical cancer, the study concluded.
The rise in these cancers has been recognized by doctors and treatment institutions in the United States and other countries, caused by HPV16, but the extent was unclear until this publication. If that trend continues, that type of oral cancer will become the nation’s main HPV-related cancer within the decade, surpassing cervical cancer.
“This is the first definitive evidence that these changes at the population level are indeed caused by HPV infection,” said Dr. Maura L. Gillison, the senior author of the new study and the chairwoman of cancer research at Ohio State University. Dr. Gillison has been a prominent researcher in the HPV-oral cancer arena since 1999, and her work which has been published in numerous peer reviewed journals has elucidated the connection of the virus to oral cancer, the demographics of those who get oropharyngeal cancers as a result of infection with it, mechanisms of transfer between individuals, and more.
Dr. Kevin J. Cullen, director of the Greenebaum Cancer Center at the University of Maryland, quoted in the New York Times, said the study was well done. “It’s very clear that this is becoming a major epidemic,” he added. He said his own research team had found similar increases in throat cancers in Baltimore during the last 30 years. Researchers think the trend may be attributable to increases in oral sex, particularly among younger people who think it is safer than intercourse.
Dr. Gillison said the increase in oral cancers was not a cause for panic as they still are not common when compared to other large incidence cancers such as breast, colon, or lung. There are approximately 37,000 cases of oral and oropharyngeal cancers diagnosed each year in the US, with fewer than 10,000 cases a year caused by the virus. Most people with HPV infections do not go on to develop cancers as a result, but have the infection cleared by their own immune system.
The tumors it causes, called oropharyngeal cancers, are mostly squamous cell carcinomas, and occur in specific areas: the base of the tongue and the area just behind the mouth, including the soft palate, tonsils, and the side and back walls of the throat. Some oropharyngeal cancers are not caused by the virus, but by tobacco and alcohol; however the rates from that etiology / cause have been decreasing as smoking has declined.
Throat cancers caused by HPV respond better to treatment than those not caused by the virus. Median survival in throat cancer patients with the virus is 131 months; without it, 20 months, a significant survival advantage. The exact reason that they respond better to treatment is not clearly defined at this time. Virus-related throat cancers are far more common in men than in women, a difference that has also not been explained.
HPV is commonly found in the genital region and is transmitted by intimate contact. The CDC says that HPV infections are the most common sexually transmitted disease, and that the majority of Americans will have an infection at some point in the lifetimes, but will likely not be aware of it. Usually the immune system fights off the infection, but in some people the virus persists and causes cancer. Like many things about this particular cancer, what causes some people to be at risk and others not when exposed to the virus, has not been elucidated.
There is no screening test for oropharyngeal cancers, no equivalent of the Pap test used to find precancerous growths on the cervix, Dr. Gillison said. Oropharyngeal cancers generally are not found until symptoms start: lumpy, swollen but painless lymph nodes in the neck, or a lingering sore throat or earache, or a sensation that something is caught in the throat when swallowing.
Patients may need surgery, radiation or chemotherapy, or some combination of those treatments when fighting this cancer.
“The side effects from treatments can be horrendous,” Dr. Gillison said. “It’s a very difficult therapy to get through.”
Two vaccines, Gardasil and Cervarix, protect against HPV Type 16 and other strains of the virus that cause cancers and genital warts. But they are currently recommended only for girls, to protect against cervical cancer.
Much of the science community believes the vaccines might also prevent some throat cancers, but cannot be sure unless the vaccines are specifically tested for that purpose. The manufacturers — Merck and GlaxoSmithKline — say they have no plans to study throat cancers. But Dr. Cullen said that the vaccines were likely to prevent the throat cancers, and should be given to boys before their first sexual contacts as well. He said he had no connection to vaccine companies.
Dr. Gillison said the vaccine companies had paid for her research in the past, but had no role in this study, which was paid for by the National Cancer Institute, Ohio State University and the Oral Cancer Foundation.