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2011-02-21 05:34:27
by Kerry Sheridan Kerry Sheridan Sun Feb 20, 8:57 pm ET
WASHINGTON (AFP) US scientists have said there is strong evidence linking
oral sex to cancer, and urged more study of how human papillomaviruses may be
to blame for a rise in oral cancer among white men.
In the United States, oral cancer due to HPV infection is now more common than
oral cancer from tobacco use, which remains the leading cause of such cancers
in the rest of the world.
Researchers have found a 225-percent increase in oral cancer cases in the
United States from 1974 to 2007, mainly among white men, said Maura Gillison of
Ohio State University.
"When you compare people who have an oral infection or not... the single
greatest factor is the number of partners on whom the person has performed oral
sex," said Gillison, who has been researching HPV and cancer for 15 years.
"When the number of partners increases, the risk increases," she told reporters
at the American Association for the Advancement of Science meeting in
Washington.
Previous studies have suggested that people who have performed oral sex on six
or more partners over a lifetime face an eight-fold higher risk of acquiring
HPV-related head or neck cancer than those with fewer than six partners, she
said.
But even though the link between HPV and cervical cancer has been well known
for many years, and vaccines now exist to provide some protection, much study
remains to be done to confirm observational links and establish causes,
Gillison said.
"The cervical cancer field is 20 years ahead," she said.
"We can't demonstrate definitively that certain behaviors are associated with
risk of acquiring an infection," she said.
"The rise in oral cancer in the US is predominantly among young white males and
we do not know the answer as to why."
Researcher Diane Harper of the University of Missouri said such studies will
take time, but the oral cancer field may move more quickly by using technology
already developed for detecting HPV in cervical cancer patients.
"One of the scientific technologies that have evolved over time is the way that
we detect HPV," said Harper.
"I think that the head and neck cancer area will benefit from that because we
have gone through all kinds of different laboratory techniques to make sure we
are actually finding what we think is HPV and getting type-specific information
to go with that."
There as many as 150 different types of human papillomaviruses, and about 40 of
those can be sexually transmitted, according to the National Cancer Institute.
Some may cause genital warts, while other more high-risk varieties can cause
oral, anal, vaginal and penile cancers.
Sexually transmitted HPV infections are common and often asymptomatic, and
untreated cases in women are the main cause of cervical cancer.
Half of all sexually active Americans will get HPV at some point in their
lives, the US Centers for Disease Control and Prevention has estimated.
Two vaccines, Gardasil and Cervarix, were approved by the US Food and Drug
Administration in 2006 for HPV types that cause cervical cancer and genital
warts.
However, only 40 percent of US girls have received one dose and just 17 percent
have received all three doses in the regimen, said researchers.
A study published earlier this month in the New England Journal of Medicine
found that the HPV vaccine could prevent 90 percent of genital warts in men,
and the vaccine has also been approved against anal cancer in men and women.
Harper said she was not recommending the general population get the HPV vaccine
because research has not yet established its effectiveness past five to eight
years for cervical cancer.
"We know from all of the very good modeling studies that have been done
throughout the world that if the vaccine does not last for a minimum of 15
years, cervical cancer will not be prevented, it will only be postponed," she
said.
For now, Harper and fellow presenter Bonnie Halpern-Felsher of the University
of California San Francisco recommended that patients discuss HPV with their
doctors.
"If you talk to health care providers and certainly parents and other
educators, they are not talking to teens about oral sex, period," said
Halpern-Felsher, who has studied teenagers' attitudes and sexual behaviors.
"Teens really have no idea that oral sex is related to any outcome like STIs
(sexually transmitted infections), HPV, chlamydia, and so on."