Author: Tom Spears, Canwest News Service
Cancer doctors are starting to believe that the human papilloma — or HPV — HPV, intended to prevent cervical cancer, will likely prevent other cancers as well — and in men as well as women.
Recent research is linking the HPV virus to a variety of cancers in the head and neck, and the urinary-genital tract, says Dr. Glenn Bauman, chairman of oncology at the University of Western Ontario faculty of medicine and a radiation oncologist at the London Health Sciences Centre.
If so, the vaccine usually given to girls at the beginning of their teenage years could also benefit boys. Boys so far have not been offered HPV vaccine, although some experts argue both sexes should be vaccinated to slow the spread of papilloma.
The virus is estimated to cause 70 per cent of cervical cancers and 90 per cent of genital warts. Cervical cancer is the second most common cancer for Canadian women aged 20 to 44. A variety of recent studies has been finding the DNA from the common virus inside cancer tumours.
“I think the tip of the iceberg is this whole HPV connection with cancer,” Bauman said. “What’s interesting is that we’re finding — and we’ve known this for a while, but we’re beginning to appreciate it — that HPV plays a role in other ‘mucosal’ cancers.”
This means a variety of cancer types in the head and neck, and also the urinary tract and genital region; tonsils, pharynx, the base of the tongue, the upper digestive tract; also the vulva, penis, vagina and anal canal. None of these is as common as cervical cancer. HPV doesn’t appear to cause prostate cancer, the most common cancer in men’s reproductive system.
This month, a McGill University study of heterosexual couples found that more than half of young adults engaged in a new sexual relationship were infected with HPV. Of this group of young adults, 44 per cent had the type of HPV that causes cancer.
HPV vaccine, which prompted controversy when officials started recommending it for Canadian girls as young as nine years old over the past few years, is too new for anyone to measure its success yet in preventing these cancers. But a wave of recent studies has been making the connection between HPV infection and developing these cancers in the first place:
• A 2007 study at Johns Hopkins Kimmel Cancer Center found that oral HPV infection is “the strongest risk factor” for a relatively uncommon throat cancer called oropharyngeal cancer, “regardless of tobacco and alcohol use.” The virus raised the risk of this cancer by 32 times compared to people with no HPV infection;
• Cancer doctors at the University of Michigan report an increase in nasopharyngeal cancer — another relatively rare form found behind the nose and above the throat — after HPV infection;
• In 2004, the Journal of the National Cancer Institute reported that DNA from the HPV virus was present in 10 to 20 per cent of all head and neck squamous cell tumours; and
• More recently, the Dartmouth Medical School in New Hampshire reported that HPV may even cause a common type of skin cancer. It cautions that sun exposure is still the main cause.
“Just the fact that a viral infection is responsible for some fairly significant cancers in people, and that we have a vaccine against it — I think that’s novel and that represents a new direction,” Bauman said.
There may turn out to be other viruses responsible for still more cancers, he suggests. He also suspects that future research will show that the environment inside the body plays a big role, especially if someone suffers from a chronic form of inflammation.
“We’ve seen quite a dramatic decrease in stomach cancers” in recent years, and he suspects that big improvements in treating stomach ulcers and gastritis (using antibiotics) may have helped.