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Cross-Protection Against Nonvaccine Types of Oncological Human Papilloma Virus (HPV) Observed With Vaccine: Presented at ICAAC

By Ed Susman

CHICAGO, IL -- September 20, 2007 -- Gardasil® (quadrivalent human papillomavirus recombinant vaccine), which protects women against the major causes of cervical cancer -- human papilloma virus (HPV) types 6, 11, 16, 18 -- appears to provide substantial cross-protection against other types of cancer-causing HPV.

Among women vaccinated with Gardasil, study findings show a 38% reduction in precancerous lesions caused by 10 virus types that are not part of the Gardasil formulation (P <.05), researchers said here at the 47th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

"We had hoped that we would see some cross-protection against other strains of human papilloma virus," said Darron Brown, MD, Professor of Medicine, Immunology and Microbiology, Indiana University School of Medicine, Indianapolis, Indiana. "This is very good news for women because they are getting extra protection with the vaccine."

Types 6 and 11 of HPV are responsible for about 90% of genital warts, while types 16 and 18 account for 70% of the cancers and precancerous lesions associated with the HPV virus, Dr. Brown said during his poster presentation on September 19th.

In two previous studies -- "Females United To Unilaterally Reduce Endo/ectocervical Disease" (FUTURE I and II) trials -- Dr. Brown and colleagues showed that Gardasil was virtually 100% successful in preventing infection with HPV types 6, 11, 16, and 18. There are, however, at least 15 other types of HPV that are also oncogenic.

"The high degree of cross-protection against additional oncogenic human papilloma virus types may provide an extra measure of protection for young women vaccinated with the quadrivalent human papilloma virus vaccine," said Dr. Brown.

Dr. Brown presented data on the preplanned substudy of his previous Gardasil studies. The data were obtained by following more than 17,000 women who participated in FUTURE I and II.

Types 31, 33, 35, 52, and 58 -- all biological "cousins" of type 16 -- were identified in precancerous lesions among 26 women out of 4,616 who received the vaccine, Dr. Brown said. Precancerous lesions caused by those same types were identified in 48 women out of 4,675 who received a placebo instead of the active vaccine. The difference represented a 45% reduction in risk of developing precancerous lesions from nonvaccine HPV sources (confidence interval 10-68).

There was a similar reduction in "cousins" of type 18 -- eight cases among vaccinated women and 15 cases among those who received placebo. The small number of cases, however, prevented this difference from achieving statistical significance.

Overall, looking at 10 oncological types of HPV, including two types that are unrelated to types 16 and 18, the researchers observed a 38% protective effect with the use of the vaccine.

There were 38 cases of cervical intraepithelial neoplasia or adenocarcinoma in situ among the women who received the vaccine -- all caused by nonvaccine-targeted HPV types -- compared with 62 cases of those precancerous lesions in the nonvaccinated women. These additional 10 oncological types of HPV account for up to 20% of cervical cancers, Dr. Brown said.

About 11,000 women in the United States will be diagnosed with cervical cancer this year and about 3,600 women in the United States will die from the disease, Dr. Brown said. Worldwide, cervical cancer will kill more than 250,000 women this year.

Funding for the FUTURE studies was provided by Merck.

[Presentation title: HPV type 6/11/16/18 Vaccine: First Analysis of Cross-Protection Against Persistent Infection, Cervical Intraepithelial Neoplasia (CIN), and Adenocarcinoma In Situ (AIS) Caused by Oncogenic HPV Types in Addition to 16/18. G-1720b]

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