HPV, ungeschützter Oralverkehr und Hals-Rachen-Krebs:
Oral sex, STDs causing increase in oral cancers
Sexual practices leading to higher rates
By Pamela Fayerman, Vancouver Sun September 2, 2010
Dr. John Hay of BC Cancer Agency in Vancouver says boys should be vaccinated for the cancer-causing HPV virus.
Photograph by: Mark Van Manen, Vancouver Sun, Vancouver Sun
VANCOUVER - The same sexually transmitted virus that causes cervical cancer is fuelling the growth of some types of oral cancers — and oral sex is believed to be the main conduit, according to experts in B.C. and around the world.
While smoking and heavy alcohol drinking were once the main risk factors for oral cancers, now the
human papillomavirus (HPV) has become a more dominant cause as smoking rates wane.
At least one strain of HPV has been identified as the main cause behind the increase in oral cancers — properly called
oropharyngeal cancers — in places such as the base of the tongue and around the tonsils, even when they’ve been removed.
The emergence of HPV-caused oral cancers is also attributed to changes in sexual practices over the past three or four decades.
“HPV has been around for ages, but the use of oral contraceptives starting in the 1960s and ’70s led to an increase in incidents of sexually transmitted diseases,” said Dr. John Hay, a radiation oncologist at the BC Cancer Agency, referring to the fact that
the pill unleashed more sexual freedom, but that also meant that HPV and other STDs became ubiquitous.
Indeed, up to
80 per cent of sexually active people contract at least one of the 100 subtypes of HPV by the age of 50; in the vast majority, the
immune system knocks the virus out.
In women, HPV thrives in the cervix and vagina.
In gay men, it can wreak havoc in the anal area.
In heterosexual men, it becomes established anywhere in the genitalia.
More than 100 cases of oropharyngeal cancers are being diagnosed annually in B.C. [4 Millionen Einwohner]. In 60 per cent of those oropharyngeal cancers, an HPV infection is confirmed as the cause. As in many jurisdictions around the world, that represents a 50-per-cent increase in the proportion of oral cancers that are HPV-related over the past 10 to 20 years.
Since 2000, the number of HPV-positive oropharyngeal cancers have nearly doubled, from 30 to 60 cases a year in men. In women, the increase has been steady, but less dramatic. The growth in incidence was documented in a recent issue of the journal Cancer by a BCCA research team.
A seminal Swedish study showed that in the 1970s, 23 per cent of oral cancers were HPV-linked. By 2006, the number had climbed to 93 per cent. (A U.S. study recently showed that up to 80 per cent of oral cancer biopsies were HPV positive, a doubling of the proportion in 10 years).
HPV vaccines are now recommended for girls and women aged nine to 26 to protect against cervical cancer but, as Hay points out, there is not yet a recommendation for boys to get the same vaccine so “only half” the population is being protected against the strains of the virus that cause cervical cancer and HPV oral cancers.
“Boys should be getting vaccinated, too, but we haven’t yet seen the same push for that as we did for girls and cervical cancer, even though there is now a worldwide recognition that we are seeing a significant increase in these types of oropharyngeal cancers and it would make sense to vaccinate both girls and boys,” Hay said.
He said at current vaccination rates (only about 60 per cent of eligible girls have been vaccinated so far) it could take a few decades for the HPV vaccine to have an effect in reducing both cervical and oral cancer rates.
In professional journals for dentists, there has been much discussion about the role such professionals could play in detecting oral cancers.
Dr. Ed Curtis wrote in the Academy of General Dentistry’s monthly newsletter, AGD Impact, that oral cancers are the kind dentists “whisper about” because of their association with oral sex. At a lunch meeting with colleagues, he noted that one made the observation that
“more cancer is happening because kids don’t think that oral sex is really sex.”
Hay said he can’t comment on that, but the good news is that unlike oral cancers caused by smoking and drinking — usually affecting the front of the tongue, floor of the mouth, cheeks and gums — those caused by HPV have a better prognosis, even if they aren’t caught until they have spread to the neck lymph nodes, as is often the case.
The better outcomes are because the
HPV-positive tumours respond well to radiation and chemotherapy.
HPV-caused oral cancers have a five-year survival rate of about 75 per cent, whereas more advanced oral cancers caused by smoking are about half that.
Dentists are being urged by various patient groups to play a bigger role in identifying oral cancers and, in B.C., an oral cancer prevention program has been picking up steam for the past few years. Dr. Michele Williams, a dental surgeon affiliated with Vancouver General Hospital and the prevention program, said HPV is now “very topical in dentistry.”
“Our [prevention] team consists of dentists, physicians and scientists who share common interest in better understanding oral cancer,” she said in an e-mail. “We are about to publish on the topic of HPV/oral cancer and are working closely with organized dentistry in this province to develop a related consensus statement and education materials for the dental team.”
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