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Oral-Genital Sex & Throat Cancer
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"Oral sex can cause throat cancer"
09 May 2007
NewScientist.com news service
Maura Gillison, Johns Hopkins Bloomberg School of Public Health
New England Journal of Medicine
People who have had more than five oral-sex partners in their lifetime are 250% more likely to have throat cancer than those who do not have oral sex, a new study suggests.
The study publication in the NEJM says this:
"Certain kinds of sexual behavior were significantly associated with oropharyngeal cancer after adjustment for confounding variables (Table 2). The association with oropharyngeal cancer increased significantly with the number of vaginal-sex partners or oral-sex partners (P for trend=0.002 and 0.009, respectively) and was markedly elevated among patients with a high lifetime number of such partners (Table 2)..... A high lifetime number of oral-sex or vaginal-sex partners, engagement in casual sex, early age at first intercourse, and infrequent use of condoms each were associated with HPV-16-positive oropharyngeal cancer.... Our data suggest that oral HPV infection is sexually acquired. Oral-genital contact was strongly associated with oropharyngeal cancer, but we cannot rule out transmission through direct mouth-to-mouth contact or other means."
The researchers believe this is because oral sex may transmit human papillomavirus (HPV), the virus implicated in the majority of cervical cancers.
The new findings should encourage people to consistently use condoms during oral sex as this could protect against HPV, the team says. Other experts say that the results provide more reason for men to receive the new HPV vaccine.
Maura Gillison at Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, US, and colleagues collected blood and saliva samples from the throats of 100 patients diagnosed with cancers of the tonsils or back of the throat. The scientists also took samples from 200 healthy people for comparison.
By combining the blood and saliva samples with antibody molecules, Gillison's team could tell whether a person had ever had an HPV infection.
All of the study participants provided information about their sexual history, including the number of people with whom they had engaged in oral sex.
After controlling for other risk factors for throat cancer, such as drinking and smoking, the analysis revealed that people who had prior infection with HPV were 32 times as likely to have this cancer as those with no evidence of ever having the virus. And those who tested positive for a particularly aggressive strain of the virus, called HPV-16, were 58 times more likely to have throat cancer.
By comparison, either smoking or drinking increases the risk of such cancer by about threefold.
The throat cancers analysed in the new study mostly started in the "crypts" of the throat - the grooves at the base of the tonsils. This might be because the tonsil grooves trap infectious particles, suggests Mark Stoler of the University of Virginia in Charlottesville, US, who was not involved in the study.
The study also revealed a link between oral sex and throat cancer caused by HPV. People who had one to five oral-sex partners in their lifetime had approximately a doubled risk of throat cancer compared with those who never engaged in this activity - and those with more than five oral-sex partners had a 250% increased risk.
There was an even stronger link between oral sex and throat cancers clearly caused by HPV-16 (those tumours that tested positive for the strain). People with more than five oral sex partners had a 750% increased risk of these HPV-16-caused cancers.
"This study is important because it is putting all of the pieces together," says Gillison. "We need to add oral HPV infection to the list of risks for oral cancer," she adds.
Virus vaccine
A vaccine against several of the most aggressive strains of HPV linked to cervical cancer received approval from the US Food and Drug Administration in 2006. However the plan to vaccinate adolescent girls with this vaccine developed by Merck, called Gardasil, has received some criticism.
There have been no studies investigating whether the vaccine can also protect against throat cancer, but the new evidence linking HPV to throat cancer could lead to broader vaccination with Gardasil. "We will see a push for vaccination in men," says Stoler, who has been involved in the development of the vaccine.
Tonsil and throat cancers affect about two in every 100,000 adults in the US. The new results could promote the development of spit tests for HPV infection to help identify people at high risk for these cancers, researchers say.
Journal reference: New England Journal of Medicine (vol 356, p 1944)
"Oral sex linked to mouth cancer"
25 February 2004
I looked up this study and found this information in the study:
"We did not observe an association between sexual behavior indicators, such as lifetime number of sexual partners and the practice of oral sex, and overall risk for cancer of the oral cavity or oropharynx:
.....In multivariable models, after adjustment for age, sex, country, drinking alcohol, smoking tobacco, and chewing tobacco, as appropriate, detection of HPV DNA in tumors was not statistically significantly different by age, sex, country, or alcohol use (data not shown). However, HPV DNA was detected less frequently in biopsy specimens from ex-smokers (OR for detection of HPV DNA = 0.6, 95% CI = 0.2 to 1.5) and current smokers (OR = 0.4, 95% CI = 0.2 to 0.9) than in biopsy specimens from nonsmokers. In India, HPV DNA was detected less frequently in tumor specimens from tobacco chewers (OR for HPV detection = 0.5, 95% CI = 0.1 to 2.0) than in those from non-chewers. Case patients reporting more than one sexual partner in their lifetime were more likely to have HPV DNA in their tumors than those reporting only one sexual partner (OR for HPV detection = 2.4, 95% CI = 1.0 to 5.7), as were those reporting a history of oral sex compared with those without such a history (OR for HPV detection = 3.2, 95% CI = 1.5 to 6.4). The association of HPV DNA with sexual behavior was similar for cancers of the oral cavity and oropharynx, although some of the estimates were not statistically significant (data not shown)...... HPV was detected more commonly in biopsy specimens from cancer patients with more than one sexual partner and from those who practiced oral sex than in biopsy specimens from those with fewer than two partners or who did not engage in oral sex, suggesting the possibility of sexual transmission."
Oral sex can lead to oral tumours. That is the conclusion of researchers who have proved what has long been suspected, that the human papilloma virus can cause oral cancers.
The risk, thankfully, is tiny. Only around 1 in 10,000 people develop oral tumours each year, and most cases are probably caused by two other popular recreational pursuits: smoking and drinking. The researchers are not recommending any changes in behaviour.
The human papilloma virus (HPV), an extremely common sexually transmitted infection, has long been known to cause cervical cancers. Several small studies have suggested it also plays a role in other cancers, including oral and anal cancers.
"There has been tremendous interest for years on whether it has a role in other cancers. Many people were sceptical," says Raphael Viscidi, a virologist at Johns Hopkins University School of Medicine in Baltimore, Maryland, a member of the team that did the latest work.
The researchers, working for the International Agency for Research on Cancer in Lyon, France, compared 1670 patients who had oral cancer with 1732 healthy volunteers. The participants lived in Europe, Canada, Australia, Cuba and Sudan. HPV16, the strain seen most commonly in cervical cancer, was found in most of the oral cancers too.
The people with oral cancers containing the HPV16 strain were three times as likely to report having had oral sex as those whose tumour did not contain HPV16. There was no difference between men and women in terms of how likely the virus was to be present in the cancers. The researchers think both cunnilingus and fellatio can infect people's mouths.
Patients with mouth cancer were also three times as likely to have antibodies against HPV as the healthy controls. For cancers of the back of the mouth, the link was even stronger.
The results prove the connection between HPV and oral cancer beyond any reasonable doubt, Viscidi says. "This is a major study in terms of its size," he says. "I think this will convince people."
Cancer specialist Newell Johnson of King's College London agrees. "We have known for some time that there is a small but significant group of people with oral cancer whose disease cannot be blamed on decades of smoking and drinking, because they're too young," he says.
"In this group there must be another factor, and HPV and oral sex seems to be one likely explanation. This study provides the strongest evidence yet that this is the case."
Genital HPV infections are common. At any one time, around a third of 25-year-old women in the US are infected. It is thought that only 10 per cent of infections involve cancer-causing strains, and that 95 per cent of women will get rid of the infection within a year. But even this does not explain why so few develop cancer.
The latest findings could improve treatments of oral cancers. Many scientists think that HPV infection must persist for tumours to grow, so giving antiviral drugs to people with oral cancers caused by the virus could improve their chances of recovery.
Prevention could soon be a possibility as well. Several research groups are developing vaccines against HPV, intended to reduce the 250,000 deaths worldwide each year due to cervical cancer. It is thought the vaccines would prevent oral infections as well as genital infections.
Journal reference: Journal of the National Cancer Institute (vol 95, p 1772)
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