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Nov. 4, 2009 -- An experimental human papilloma virus ( HPV) vaccine shows early promise for preventing genital cancer in high-risk women who are already infected with the virus.
Infected women with precancerous lesions caused by HPV showed regression of the lesions after being given the experimental vaccine in a study reported today by researchers from the Netherlands in the New England Journal of Medicine.
The study included just 20 women. Researchers tell WebMD they are working to improve the vaccine before moving on to larger trials.
But the findings suggest it may be possible to prevent genital cancers by vaccinating HPV-infected women at high risk for developing the disease. "We were able to successfully treat women with these HPV-caused lesions," study researcher Gemma G. Kenter, MD, PhD, says. "And we were able to show lesion regression over a two-year period."
The two commercially available HPV vaccines, Gardasil and Cervarix, are designed to prevent initial infection with specific strains of the sexually transmitted HPV virus that cause most cervical cancers.
Because of this, they are most effective when given before the onset of sexual activity. The CDC recommends that the vaccine be given to girls between the ages of 11 and 12 and that it not be given to women older than 26.
Like the commercially available vaccines, the experimental vaccine targets the HPV 16 virus, which is a leading cause of cervical cancer and other genital cancers.
The women in the study all had the precancerous genital lesions, known as vulvar intraepithelial neoplasia (VIN), which put them at high risk for developing cancer of the vulva. The lesions were also advanced enough to require treatment.
The women were vaccinated up to four times with the experimental vaccine.
Three months after treatment, 12 of the 20 women had clinical responses and reported relief of symptoms such as persistent itching. Five of the women had complete regression of their lesions and evidence of HPV-16 infection was no longer detectable in four of them.
Two years after treatment, about half the women no longer had the lesions and had no symptoms.
"Since the rate of spontaneous regression of lesions in patients with (advanced) VIN is low (less than 1.5%), the high response rate observed in the current trial is probably related to the vaccination," the researchers write.
Cancer vaccine researcher Olivera J. Finn, PhD, of the University of Pittsburgh School of Medicine, calls the new research "very promising."
She tells WebMD that an effective vaccine for the treatment of patients who already have cancer has proven to be an elusive goal.
The findings suggest that more effective immune responses can be generated in high-risk people before cancer develops.
"When things start to progress toward cancer we may be able to arrest this with a vaccine," she tells WebMD. "As immunologists, we have known that this was a possibility for some time."
If the experimental vaccine is proven safe and effective in larger trials, Finn says it may one day offer women who are too old to get the currently available HPV-prevention vaccine protection against cervical cancer, even if they don't have infection-related symptoms.
"Right now if a woman is over 30, we have very little to offer her," she says.