NEW YORK - Cancer of the back of the mouth and throat is on the rise, primarily because of the spread of a viral infection called human papillomavirus (HPV), researchers report in a new study.
Dr Maura Gillison at the Ohio State University and her colleagues studied throat tumour samples collected over a 20-year period and found that the number of people who were diagnosed with HPV-linked oral cancer in 2004 tripled the number in 1988, surging to 72 per cent from about 16 per cent.
The type of throat cancer they examined, called oropharyngeal, originates in the back of the tongue, the soft part of the roof of the mouth, the tonsils, or the sides of the throat.
The study, published in the Journal of Clinical Oncology, estimates that HPV-linked oral cancers now afflict 26 out of every million people in the United States, compared to eight out of every million people in 1988.
HPV-linked oral cancers strike men more than women, although it is unclear why, Gillison said.
By 2020, HPV-linked throat tumours will have become more common than HPV-linked cervical cancer and may even surpass smoking as the leading cause of throat cancers.
Previously, tobacco had been the primary cause of oral cancer, and most oral cancer cases were HPV-negative. Gillison's group found that HPV-negative cancers have been cut in half since the 1980s.
Researchers suspect this is due to changes in sexual behavior that have helped spread the virus.
HPV is a very common sexually transmitted infection known for infecting genitals, and can also spread to the throat through oral sex and cause cancer.
Dr. Tina Dalianis, a professor at the Karolinska Institute in Sweden who did not participate in this research, said she believes the increase in oral cancers "is due to an HPV epidemic."
"We believe that sexual habits have changed, and that there is an increase in sexual activity earlier on in life, with an exchange of many more sex partners in general," she wrote in an email to Reuters Health.
"This whole relationship between HPV-related head and neck cancer completely changes our ideas of who is at risk, how to treat the cancer, the prognostics of the cancer, and prevention," Gillison told Reuters Health.
The good news is that people diagnosed with the HPV-positive form of the cancer have a better prognosis, she said, and the cancer is more responsive to treatment.
There is also a potential opportunity for prevention using an HPV vaccine that is approved to prevent anal and cervical cancer, Gillison said.
If the vaccine can prevent these HPV-caused cancers, perhaps it can work for oropharyngeal cancers too, she added.
The findings may put pressure on Merck & Co., the second largest drugmaker in the US, to conduct large scale trials on its cervical vaccine Gardasil, to see if it also protects against HPV throat infections, Bloomberg reported.