Researchers affiliated with the Quadrivalent HPV Vaccine Merck Study Group have reported that vaccination against human papillomavirus (HPV) is associated with a reduction in Pap tests, colposcopy, cervical biopsy, and definitive treatment among women who were uninfected at the time of vaccination. The details of this study were presented at the 39th annual meeting of the Society of Gynecologic Oncologists (SGO) in Tampa, Florida, from March 9 to 12, 2008.

Pap smears have decreased the incidence and death rate of cervical cancer among women in developed countries such as the United States. Cervical cancer is caused by specific high-risk strains of HPV, which can be detected by a special test called Hybrid Capture II (made by Digene).

Now that an HPV vaccine (Gardasil®, manufactured by Merck) has been approved by the U.S. FDA, further reductions in cervical cancer incidence and death may be anticipated. Gardasil is a quadrivalent vaccine because it confers protection against four subtypes of HPV (HPV 6 and HPV 11, which cause 90 percent of genital warts, and HPV 16 and HPV 18, which cause 70 percent of cervical cancers).

Despite the success of Pap smear programs and the ability to detect HPV, over 2 billion dollars in healthcare expenditure occurs annually as a result of abnormal Pap tests and their subsequent evaluation, which often requires cervical biopsies and other surgical procedures on the cervix. This is because, although Pap smears and HPV detection allow a pre-cancerous or dysplastic state of the cervix to be detected and treated before it can turn into cancer, neither of these two methods eliminate the original problem, which is infection with HPV.

The end-of-study data from three pivotal Phase II/III clinical trials of the quadrivalent HPV vaccine were reported at the SGO meeting. A total of 18,150 16 to 26-year-old women were enrolled in one of three randomized, placebo-controlled trials. Vaccine or placebo was given at Day 1, Month 2, and Month 6. Subjects underwent Pap testing on Day 1 and every six to 12 months for up to 48 months. Patients with specific abnormalities on the Pap smear were referred for colposcopy and, depending on the findings, definitive treatment was carried out.

After an average follow-up period of four years, the investigators noted a reduction in Pap tests, colposcopy, cervical biopsy, and definitive treatment among women who were uninfected with HPV at the time of vaccination. Interestingly, these reductions were seen irrespective of the specific type of HPV involved.

Comments: Vaccination with the quadrivalent vaccine appears to be able to decrease the number of Pap tests, colposcopies, cervical biopsies, and treatment women require. This occurs presumably because the vaccine protects against infection with HPV, which is the inciting event in the development of pre-cancerous cervical disease. Long-term studies are required to determine the duration of protection that is achieved by the three-dose vaccination series.

Related News:

HPV Testing Superior to Papanicolaou Testing for Cervical Cancer Screening (11/3/2007)

HPV Vaccination Recommended for Boys and Girls for Prevention of Head and Neck Cancers (10/15/2007)

HPV Vaccine, Cervarix™, not Therapeutic in Women with Preexisting Infection (8/22/2007)

Cervical HPV Disease Associated with High Cost and Decreased Quality of Life (5/25/2007)

Results of Three Randomized Trials of Gardasil® Vaccine for HPV Summarized (5/22/2007)

Prevalence of HPV in the U.S. Greater than Previously Thought (3/1/2007)

Reference: Huh WK. 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. 39th Annual Meeting of the Society of Gynecologic Oncologists, Tampa, FL, Plenary Session III, 10 March 2008, Abstract #20. Gynecologic Oncology. 2008;108:S10.