Abnormal Pap Tests Decline Among Women Who Received Human Papillomavirus Vaccine: Presented at SGO

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Title: Abnormal Pap Tests Decline Among Women Who Received Human Papillomavirus Vaccine: Presented at SGO
URL: http://www.pslgroup.com/dg/21E5DE.htm
Doctor's Guide
March 14, 2008

By Ed Susman

TAMPA, Fla -- March 14, 2008 -- Women who received a quadrivalent vaccine against four of the major types of human papillomavirus (HPV) have far fewer abnormal Papanikolaou (Pap) tests than women who received placebo injections.

"The highest reductions -- about a 43% decreased risk -- were observed among cases of high-grade squamous intraepithelial lesions and for definitive therapy -- a 42% decreased risk," said Warner K. Huh, MD, Associate Professor and Chair of Obstetrics and Gynecology, University of Alabama at Birmingham, Birmingham, Alabama.

In his presentation here at the Society of Gynecologic Oncologists (SGO) 2008 Annual Meeting on Women's Cancer, Dr. Huh said that in the 3.3 years of follow-up, researchers were already seeing the impact of the vaccine, which is 98% to 100% effective in preventing infection with HPV types 16 and 18 (responsible for 70% of cervical cancer cases) and types 6 and 11 (responsible for about 90% of genital warts).

Dr. Huh and colleagues analysed data from clinical trials of the vaccine that enrolled more than 18,000 women. The data Dr. Huh presented involved women who were assigned either to the vaccine or to placebo. The studies included in the analysis were all funded by Merck & Co. After researchers observed early results that the vaccine was more effective in preventing infection, the placebo patients were offered treatment with the active product. Dr. Huh noted this effectively ended the comparative research.

However, with 3.3 years of use, the researchers were able to see significant reductions in all aspects of abnormal Pap tests.

There were 285 (5.9%) cases of atypical squamous cells of undetermined significance among the 4,870 vaccinated subjects for whom data were available, compared with 359 (7.6%) cases found on the Pap tests of 4,758 women on placebo -- a 23% reduction.

There were 864 (17.7%) cases of low-grade squamous intraepithelial lesions among the vaccine group compared with 1000 (21.0%) cases among the placebo cohort -- a 16% reduction.

There were 59 (1.2%) cases of atypical squamous cells -- cannot exclude high-grade squamous intraepithelial lesion (HSIL) -- in the vaccine group compared with 89 (1.9%) cases in the placebo group -- a 35% reduction.

There were 24 (0.5%) cases of HSIL -- the most serious Pap test lesion -- in the vaccine group compared with 41 (0.9%) in the placebo patients -- a 43% reduction.

There were 132 (2.7%) women in the vaccine group who required definitive treatment for the lesions compared to 230 (4.8%) women in the placebo group -- a 42% reduction in treatment-related therapy.

All the differences reached statistical significance with confidence intervals well above unity.

While the vaccine only protects against four of the 100 or so HPV types, Dr. Huh said the reductions in abnormal Pap tests occurred irrespective of the HPV type involved.

[Presentation title: Impact of Quadrivalent Human Papillomavirus (HPV) Types 6/11/16/18 L1 Virus-Like Particle Vaccine on the Incidence of Abnormal Pap Tests and Cervical Procedures. Abstract 20]

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