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Multiple HPV
infections boost cervical cancer risk

Multiple HPV
infections boost cervical cancer risk

Women who become infected with multiple strains of the virus linked to cervical cancer may have a particularly high risk of developing the disease, new research suggests.

In a study that followed more than 2,400 Brazilian women, researchers found that those who became infected with more than one type of human papillomavirus were far more likely than women infected with one viral strain to develop precancerous changes in the cervix.

There are more than 100 types of HPV, some of which cause genital warts. Certain strains of genital HPV can cause abnormalities in the cervical tissue known as "high-grade" lesions, which can sometimes progress to cancer.

The new findings suggest that women who become infected with multiple strains of HPV are at particular risk of developing these lesions. The results could have implications for cervical cancer screening and diagnosis, said senior study author Eduardo Franco of McGill University in Montreal.

Many experts already believe that cervical cancer screening could be improved by routinely running genetic tests to detect cancer-related HPVs in cervical cell samples, along with doing standard Pap tests.

Genetic analysis of HPV types, Franco told Reuters Health, could tell doctors which women harbor more than one strain and may need to be followed more closely to catch precancerous lesions early.

"This is one more piece of evidence for why we would eventually need to test for HPV in the general population" as part of cervical cancer screening, Franco said.

The study, which is published in the journal Cancer Epidemiology, Biomarkers & Prevention, included 2,462 women ages 18 to 60 who underwent multiple HPV tests over four years. The tests were more sophisticated than those used in clinical practice, which basically give a "yes" or "no" as to whether a woman has a high-risk HPV type. They instead specifically identified roughly 40 genital HPV types, including high- and low-risk types.

At any one test, Franco's team found, 2% to 3% of the women were infected with multiple HPV strains. Many more--22%--tested positive for different HPV types at some point over the four years. And as a group, these women were at particular risk of developing precancerous lesions.

Compared with women who tested negative for HPV throughout the first year of the study, those infected with one HPV type were 41 times more likely to develop high-grade cervical lesions. But the risk was 92 times greater for women who'd been infected with two or three HPV types, and more than 400 times higher for those with four to six viral types.

The combination of HPV-16 and HPV-58 appeared particularly risky, the researchers found. HPV-16 is one of four viral types targeted by the recently approved HPV vaccine Gardasil. The vaccine does not prevent HPV-58 infection, but it would be expected to take away the risk of "coinfection" with HPV-16, Franco noted.

It's uncertain why infection with multiple HPV strains raises the odds of precancerous lesions, Franco said. It could be the direct effect of the viruses themselves, he explained, but it's also possible that multiple infections signal a "faltering of the immune system" in some women, as the body's defenses are usually able to vanquish HPV. (Reuters)

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