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HPV and Cancer Risk

Health professionals are aware of the link between the human papillomavirus (HPV) and cervical cancer. But they may be less aware that HPV also causes other cancers including rare cancers of the vulva, vagina, penis, and anus. Evidence also indicates that it causes oropharyngeal cancers (those at the back of the tongue and the throat).
“HPV has a propensity to infect tissue that can then become cancerous,” says Dr. Stephanie Snow, a medical oncologist with the Capital Health Cancer Care Program.
Of the many strains of HPV, Dr. Snow says certain strains of HPV are of a higher risk for cancer than others. “For oropharyngeal cancers, the key culprit is HPV 16.”

It is well known that HPV is sexually transmitted, but researchers are still trying to determine how the virus invades areas of the body like the throat. “It’s not clear if the cause is oral sex or kissing or transmission via saliva. We don’t know the root of this yet,” says Dr. Snow.

HPVThe incidence of head and neck cancers as a group, she adds, is decreasing – with one exception. “The one area where they are increasing is the oropharyngeal cancers.” A recent study published in The New England Journal of Medicine demonstrated that HPV exposure and infection increased the risk of oropharyngeal squamous cell cancer independently of tobacco and alcohol use, two other important risk factors for the disease.

For patients with HPV-related cancers, there is some hopeful news. “When the virus causes cancer, it is not usually as aggressive as other cancers,” notes Dr. Snow.

The symptoms may also differ. When HPV is the cause of a neck cancer, it spreads quickly to the lymph nodes. “There may be a lump in the neck that does not go away. This should always be checked,” says Dr. Snow. “In non-HPV cancer, the first symptom is usually a sore throat.”

HPV has long been known to cause cervical cancer. “It’s a DNA virus that causes 100% of this cancer,” says Dr. Rob Grimshaw, Medical Director of Cancer Care Nova Scotia’s Cervical Cancer Prevention Program.

Upwards of 85% of young women in Nova Scotia are addressing this risk by being vaccinated against HPV. “It’s best to give the vaccine before young women are sexually active,” notes Dr. Grimshaw. “In most schools, this is done in grades seven and eight.”

Eventually the vaccine may also be given to young men in Canada, says Dr. Snow. “But we would first need public health policy to do this.”

The Centre for Disease Control in the US has endorsed vaccination of boys with the HPV vaccine. This makes good sense in the US as vaccine programs there only appear to be reaching 40% of the target age girls. The vaccine programs in Canada have been much more successful, for instance, reaching 85% of girls in Nova Scotia. This reduces the need for vaccinating boys, as males are still benefitting if their female sexual partners have been vaccinated. One study conducted in Australia found that the incidence of genital warts, also caused by HPV, dropped in young men in the wake of a vaccination program for young women. “The males still got protection, by reducing HPV transmission through the vaccination of females,” says Dr. Grimshaw.

He points out, however, that vaccinated women are not fully protected from cervical cancer and need to have regular Pap smears. “HPV has lots of subgroups. The vaccine covers two strains that cause 70% of cancers. Still, regular screening remains important for the rest of their lives.”

Health professionals can lend a helping hand to reduce risk and increase awareness. Patient education is important. “Cancer patients and their families often feel more comfortable speaking to their family doctor. Often there is guilt with this type of cancer,” says Dr. Snow.

“The bottom line,” she adds, “is that no sex is safe sex. Health professionals need to be able to talk to their patients, especially their young patients, and educate them about how to protect themselves.”