The vaccine against human papillomavirus (HPV) subtypes 16 and 18, marketed as Cervarix (GlaxoSmithKline) to prevent cervical cancer, might also protect against oropharyngeal cancer.
In the Costa Rica HPV Vaccine Trial, published online July 17 in PLOS ONE, the vaccine reduced oral HPV infections in women by more than 90%.
"The analysis is unique because it is the first demonstration of the efficacy of the bivalent vaccine (Cervarix) to prevent HPV 16 and 18 infections in the oral cavity," first author Rolando Herrero, MD, PhD, head of the prevention and implementation group, International Agency for Research on Cancer (IARC), World Health Organization, Lyon, France, told Medscape Medical News.
"These viruses are associated with an important and growing fraction of cancer of the oropharynx and tonsils. In terms of impact on clinical practice, the potential for protection against these infections is an additional reason to vaccinate people with this vaccine, particularly before exposure to the virus," Dr. Herrero explained.
The study, a collaborative effort between IARC, Costa Rican investigators, and the US National Cancer Institute, was initially designed to evaluate the vaccine's efficacy against cervical cancer. It later evaluated efficacy at other anatomic sites, including the oral cavity.
"Tantalizing Preliminary Evidence"
In 2004 and 2005, 7466 healthy women 18 to 25 years of age were enrolled in the trial. The women were randomly assigned to receive either the HPV 16/18 vaccine or the hepatitis A vaccine (control group). Four years after vaccination, oral specimens from 5840 of the women were used to evaluate vaccine efficacy against oral HPV infection.
The vaccine was found to be effective against oral HPV 16/18 infection in 93.3% of the women (95% confidence interval, 63% - 100%). There were 15 prevalent HPV 16/18 infections in the control group and only 1 in the HPV vaccine group.
According to the researchers, this study suggests that the vaccine "affords strong protection against oral HPV 16/18 infection, with potentially important implications for prevention of increasingly common HPV-associated oropharyngeal cancer."
But Maura Gillison MD, PhD, professor of medicine and Jeg Coughlin Chair of Cancer Research at The Ohio State University Comprehensive Cancer Center in Columbus, who was not involved in the study, cautions that more study is needed.
This study provides "tantalizing preliminary evidence" that the HPV vaccine might prevent oral HPV infections that could lead to cancer, Dr. Gillison told Medscape Medical News. "Oral HPV 16/18 infection was less common at a single time point 4 years after vaccination among women who received an HPV vaccine than among women who did not."
"Unfortunately, this study cannot change clinical practice or national recommendations for vaccination. It does not meet the standards of an efficacy trial that would be required for an FDA indication or to change practice recommendations," Dr. Gillison noted.
She explained that the study "was not designed to evaluate whether the HPV vaccines are effective in reducing incident or persistent oral HPV infection. Oral HPV infection was not included in the original design of the trial, so the investigators could only compare oral HPV infection prevalence at a single time point."
Questions Remain
Dr. Gillison is hopeful that this study "will encourage vaccine manufacturers and regulatory agencies to perform the definitive prospective clinical trial."
Dr. Herrero agrees that more study is needed. "There are many aspects of the disease that we still don't understand, and we need more direct evidence that the vaccine prevents oropharyngeal cancer," he said in a statement.
"We need more studies to know the duration of the protection," he told Medscape Medical News, and whether men are also protected. "If similar results are observed in men, the vaccination of boys may become an important public health measure in areas where oropharyngeal and other HPV-related cancers are relatively common in men," Dr. Herrero said.
Previous data from the Costa Rican HPV trial showed that the HPV 16/18 vaccine also protects against anal infection with these HPV types in women, as previously reported byMedscape Medical News.
The Costa Rica HPV Vaccine Trial is sponsored and funded by the National Cancer Institute, with funding support from the National Institutes of Heath Office of Research on Women's Health. The vaccine was provided by GlaxoSmithKline Biologicals. Dr. Herrero has disclosed no relevant financial relationships. Some of his coauthors report financial relationships, including 2 who are named inventors on US government-owned HPV vaccine patents licensed to GlaxoSmithKline and Merck, as detailed in the paper. Dr. Gillison reports serving as a consultant for Merck & Co, GlaxoSmithKline, Amgen, and Bristol-Myers Squibb.
PLOS ONE. Published online July 17, 2013. Abstract
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