A vaccine that targets human papillomavirus (HPV) is able to stop precancerous lesions in the vulva from progressing into full-blown malignancies, Dutch researchers report.
Two other vaccines - Gardasil and Cervarix - have been approved for young women to prevent infection with HPV, which is also thought to spur precancerous lesions in the cervix and cause 70% of cervical cancers.
But the vaccine used in this study, published in the New England Journal of Medicine, is not the same as the two existing vaccines.
Treats existing lesions
"This provides a therapeutic effect to a lesion that's already there," explained Dr Eugene P. Toy, an associate professor of obstetrics and gynaecology in the division of gynaecologic oncology at the University of Rochester Medical Centre, US.
"This shows that it is possible to vaccinate against chronic disease, as well as treat HPV-induced premalignance," added study co-author Sjoerd H. van der Burg, of the experimental cancer immunology and therapy section at the Leiden University Medical Centre in the Netherlands and ISA Pharmaceuticals, which helped fund the study and has licensed the patent for the vaccine from Leiden University Medical Centre.
Eventually, clinicians hope the two HPV vaccines on the market will reduce the incidence of vulvar precancerous lesions.
Right now, though, said Dr Kristine Zanotti, a gynaecologic oncologist with University Hospitals Case Medical Centre in Cleveland, "there are a lot of potential therapeutic challenges with HPV-related problems, especially vulvar dysplasia, which are multi-focal [they crop up in different places] and recurrent. [This vaccine] is a very exciting tool."
The HPV-16 virus is implicated in 75% of cases of these vulvar lesions. A sexually transmitted pathogen, HPV has also been linked to rare cancers of the throat, genitals and anus, as well as genital warts.
For vulvar lesions, the existing treatments are unpleasant and not altogether effective.
"What we typically do is ablative therapies that destroy the lesion. That involves a surgical procedure or topical agents that essentially slough off the lining of the affected tissue," Toy explained.
"Complete response rates [from these therapies] are disappointingly low, and we don't know if they last," added Zanotti.
For this study, 20 patients with vulvar dysplasia were vaccinated three or four times against certain cancer-related proteins associated with HPV-16.
Three months after the last vaccination, 60% of patients reported some kind of response along with fewer symptoms. For the same time period, five women (25%) saw their lesions disappear completely and four women had no more signs of HPV-16.
After a year, 79% of patients had experienced some kind of response while almost half had a complete response, which lasted at least 24 months, according to the report.
All of the patients showed immune responses to the vaccine.
Vaccine recognises infected cells
Unlike Gardasil and Cervarix, which only affect the outside of the virus, the vaccine explored in this study was "trained to sense the proteins that are produced by the virus inside the cell. As such, they can recognise virally infected or virally transformed cells," van der Burg explained.
Also exciting is the possibility, mentioned in the paper, that the new vaccine could be combined with imiquimod cream to completely erase all signs of the infection and tainted cells.
Next, the researchers want to figure out why the vaccine did not have a complete effect in all patients and they would also like to improve the vaccine so it works in patients with actual cancer or even other, non-HPV-related cancers, van der Burg said.
"In principle, this vaccine gives an enormous stimulation of the immune response against the HPV antigens expressed in infected and transformed cells. As such, it should do the same in patients with other types of HPV-16-induced (pre-)malignancies. However, in cancer patients, other forces may work against the efficacy of this vaccine. These need to be tackled, too, in order to make the vaccine do its job," van der Burg added. - (Amanda Gardner/HealthDay News)
Human Papillomavirus (HPV)