An experimental vaccine cured nearly half of women with pre-cancerous growths on their genitals, producing major improvement in nearly four out of five, researchers in the Netherlands reported on Wednesday.

We hope to get results like this in women with cancer, but those tests are in the future, team leader Dr. Gemma Kenter of Leiden University said in a telephone interview.

The vaccine is different from the Merck's Gardasil vaccine and GlaxoSmithKline's rival Cervarix, which are available to prevent cervical cancer caused by common forms of the human papillomavirus, known as HPV.

The new vaccine tested by Kenter and her colleagues is designed as a treatment for precursor growths known as vulvar intraepithelial neoplasia. Unlike Cervarix and Gardasil, it is designed to treat women who are already infected and already experiencing the growths.

We tried to find something for women who already had the disorder, Kenter said.

More than 75 percent of the growths are caused by the HPV-16 virus and treatment with topical chemotherapy, laser, or surgery is often unsuccessful.

The vaccine was tested on 20 women. Lesions disappeared in nine of the women, including one whose growths were more than 10 years old.

Another six women saw their growths shrink by at least 50 percent after one year. One woman died of sudden heart failure before her 12-month evaluation.

All patients with a complete response were still free of disease at 24 months of follow-up, the researchers wrote in the New England Journal of Medicine.

Such lesions turn cancerous in about 3,200 U.S. women each year and roughly 800 die of vulvar cancer annually.

But the vaccine did not work for everyone. Within three and a half years after vaccination, two patients developed cancer and one woman who initially showed major improvement had a relapse.

We're very happy with the results. We don't think we are there yet, but this is a big step forward, said Kenter.

Not only are the researchers trying to get a stronger effect with a lower dose, they are attempting to avoid the large bumps that sometimes appear at the injection site and, in a few women, last for two years.

That may not be a problem for those who actually have cancer. A bump on the arm is nothing compared to the complications you can have from chemotherapy, Kenter said. But for those who have minor HPV infection, you don't like local side effects.

Leiden University holds a patent for the vaccine technology and ISA Pharmaceuticals has licensed the patent.