Bay Area Reporter - August 6, 2009
Bob Roehr

Researchers at the University of Maryland Cancer Center in Baltimore looked for the presence of human papillomavirus (HVP) in oropharyngeal cancer tumors. HPV is a family of more than 100 different strains of virus that can cause vaginal, cervical, anal, and oral cancers, and warts on various parts of the body.

Dr. Kevin Cullen said patients who were treated with chemoradiation had a survival rate that was "nearly five-fold higher if they were HPV-positive than if they were HPV-negative, which is an astounding biologic effect."

The cancers caused by HPV have their own unique pattern of gene expression and susceptibility to treatment at the cellular molecular level, while similar appearing cancers caused by alcohol and tobacco abuse are much more difficult to treat, he explained.

HPV can be spread through sexual contact, but also through inadequately cleaned sex toys and fingers. There is emerging evidence that it may also spread through "deep kissing" and saliva, though probably not very efficiently.

Analysis of stored samples suggests that the percentage of all oropharyngeal cancers that are HPV-positive has increased from about 20 percent to 60 percent since about 1980, said Dr. Scott Lippman, a researcher at the M.D. Anderson Cancer Center in Houston. He called it a lagging effect of the sexual revolution.

"We are on the cusp of an epidemic of this disease. If you look at the incidence curves, this is likely to become one of the most common [head and neck] tumors that we see in the next five or 10 years," he said. It already causes more than 1,500 deaths per year in the US.

The patient population also has changed. Where patients once were older long-term abusers of tobacco and alcohol, now they are likely to be younger, male, white, and a cross-section of the population.

"It is a whole different population," said Lippman.

Racial differences

Cullen initially began his study to try to understand why blacks respond less well to chemoradiation than do whites. When he looked more closely, he saw that patients whose tumors were HPV-negative responded similarly regardless of race.

The study was part of a larger one that looked at all types of head and neck cancers. For the oropharyngeal portion, there were 169 HPV-positive and 68 HPV-negative participants. Of those, there were 27 blacks (HPV-negative) and one HPV-positive. There were 130 whites (HPV-negative) and 66 HPV-positive.

However, almost all black patients were HPV-negative, while nearly a third of white patients were HPV-positive. They were developing subtly different cancers in their mouths.

Dr. Otis Brawley, chief medical officer of the American Cancer Society, believes this difference between blacks and whites likely is tied to both biology and behavior.

The biology is that HPV is a localized sexually transmitted infection, but the immune response flows through the blood system to the entire body. So the first-exposed body site bears the brunt of the infection, but once the immune system sees the HPV it is primed to respond and better fight off an infection when other parts of the body are exposed to HPV.

And there is where behavior comes in. Blacks and whites differ in their patterns of early sexual activity, said Brawly.

"Blacks who have early genital sex actually protect their oropharynx by having their first sexual experiences as genital sex," he said.

Younger whites are more likely to engage in oral sex, often to preserve virginity, so they are more likely to first become infected with HPV in the mouth, which is likely to afford protection in the vagina and anus.

Brawley also is concerned that changing sexual practices are driving similar changes in the rates of throat cancers. Some of those can be caused by HPV while others are caused by an adenovirus. But research in this area is less developed and the risks are less clear.

Lippman is pushing for this information to be broadly disseminated. He believes it should be integrated into sexual education early in life, because exposure to HPV often occurs soon after initiating sexual activity. He said that boys, as well as girls, should receive the HPV vaccine before they become sexually active.

The study was published in advance online at the end of July in Cancer Prevention Research. It has caused the Maryland Cancer Center to immediately change its screening and treatment practices for oral cancers.

Another recent study, which examined the records of nearly a half million cancers reported to the National Cancer Registry between 1980 and 2004, found a statistically higher risk for all HPV-related cancers among persons coinfected with HIV.

The risk was greater the lower their CD4 count. This is not surprising given that an impaired immune system is less able to fight off a variety of infections. About 20 percent of all cancers are caused by HPV or some other virus.
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