A sexually transmitted infection usually thought of in connection to cervical cancer is also tied to a five times greater risk of cancer of the vocal chords or voice box, a new report suggests.
Combining the results of 55 studies from the past two decades, Chinese researchers found 28 percent of people with laryngeal cancers had cancerous tissue that tested positive for human papillomavirus (HPV).
But that rate varied widely by study, from no throat cancer patients with HPV to 79 percent with the infection.
"We're finding that HPV appears to be linked to a number of squamous cell carcinomas of the head, neck and throat," said Dr. William Mendenhall, a radiation oncologist from the University of Florida in Gainesville who didn't participate in the analysis.
However, he told Reuters Health, "I think the risk of HPV on laryngeal cancer is probably relatively low. Most of the patients we see currently that come in with laryngeal cancer have a strong history of cigarette smoking, also heavy drinking."
Along with tobacco and alcohol, having a poor diet and exposure to certain chemicals can increase a person's risk of laryngeal and other head and neck cancers.
The American Cancer Society estimates 12,360 people will be diagnosed with laryngeal cancer in the United States in 2012 and that there will be 3,650 deaths from the disease.
Along with their larger review, researchers led by Dr. Xiangwei Li, from the Chinese Academy of Medical Sciences and Peking University Medical College in Beijing, analyzed 12 studies that compared cancerous and non-cancerous tissues from a total of 638 patients. They found the cancerous throat tissue had 5.4 times the odds of testing positive for HPV infection, compared to non-cancerous tissue.
The analysis was published last week in the Journal of the Infectious Diseases Society of America.
Mendenhall said that of all head and neck cancers, HPV seems to play the biggest role not in laryngeal cancer, but in cancer of the tonsils and back of the tongue.
However, he added, "the exposure is probably decades earlier. Someone who develops a base of tongue cancer when they're 50, they probably were exposed to the virus years before, in their teens or 20s."
At least half of sexually-active people get HPV at some point in their lives, according to the Centers for Disease Control and Prevention (CDC), but the virus is usually cleared by the immune system. Only some of the 40-plus HPV strains have been tied to cancer.
Based on the current findings, it's difficult to know how many of the laryngeal cancers in the original studies were actually caused by the virus, researchers said.
But Mendenhall said extending HPV vaccination to boys and young men, as the CDC has recommended, "will hopefully reduce at least some of these HPV-related cancers."