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CHICAGO -- Vaccination against human papillomavirus (HPV) reduced the risk of multiple types of cancer in both men and women, a large retrospective cohort study showed.

The risk of head and neck cancer and all HPV-associated cancers in men decreased by more than 50%. Consistent with previous reports, vaccination reduced the risk of cervical cancer by 29%, cervical cancer precursor lesions by 50-60%, and all HPV-related cancers in women by 27%. The risk of head and neck cancer in women decreased by 33%, but the difference compared with unvaccinated women did not reach statistical significance.

The data are among the first to show an association between HPV vaccination and a reduced risk of multiple types of cancer and reduced cancer risk in men, reported Jefferson DeKloe, BS, a medical student at Western Michigan University in Kalamazoo and research fellow at Thomas Jefferson University in Philadelphia, during a press briefing ahead of the American Society of Clinical Oncology (ASCO) annual meeting.

"The HPV vaccine is a safe and effective way to prevent infection," said DeKloe. "Our study showed that patients under the age of 40 who were vaccinated for HPV usually have lower rates of cancer that are typically caused by HPV, including oropharyngeal cancer and cervical cancer."

ASCO President Lynn Schuchter, MD, of the Abramson Cancer Center at the University of Pennsylvania in Philadelphia, said the study provided important new information about the HPV vaccine's ability to protect against malignancies other than cervical cancer.

"We've known for a long time that having the HPV vaccine can prevent the development of HPV infection, yes, but importantly, cancer," said Schuchter. "We've known about it primarily from cervical cancer. This is a really important study that extends the information about the impact. It was expected that HPV vaccine would decrease the risk of cancer in other areas that are associated with HPV infection."

As the incidence of head and neck cancer (particularly oropharyngeal cancer) associated with smoking and alcohol has declined, HPV-related oropharyngeal cancer has emerged as the primary disease type.

"This study really highlights the importance of getting the HPV vaccine," said Schuchter. "The goal is that younger girls and young boys get vaccinated to prevent development of HPV infection, and that should decrease the risk of cancer, which is what we've seen. This is really important information that continues to make the case for why we need boys and girls vaccinated against HPV."

The primary objective of the study was to gather more information about the relationship between HPV vaccination and subsequent risk of HPV-related cancers. Data for the analysis came from the . The specific cancer sites of interest were head and neck, cervix, anus/anal canal, penis, vulva, and vagina. Additionally, women with no history of cervical dysplasia were followed for atypical cytology in Pap tests.

Vaccinated individuals were matched by propensity scoring to assemble a control population of unvaccinated men and women. Data analysis comprised 760,540 vaccinated men and 945,999 vaccinated women.

More than twice as many HPV-related cancers occurred in unvaccinated men (57 vs 26), which translated into a 54% reduction in the odds ratio (95% CI 0.29-0.72, P=0.0010). The data showed that 48 unvaccinated men developed head and neck cancer as compared with 21 in the vaccinated group, a 56% reduction in the odds ratio (95% CI 0.26-0.73, P=0.0016). Too few cases of anal and penile cancer occurred to permit a meaningful analysis.

Among unvaccinated women, 43 developed head and neck cancer versus 29 vaccinated women (OR 0.67, 95% CI 0.42-1.1, P=0.10). Cervical cancer occurred in 70 vaccinated participants compared with 99 in the unvaccinated cohort (OR 0.71, 95% CI 0.52-0.96, P=0.027). More vaccinated women developed vulvar/vaginal cancer (20 vs 12), but the difference was not statistically significant (OR 1.66, 95% CI 0.81-3.41). Vaccination was associated with an odds ratio of 0.73 for all HPV-related cancers (95% CI 0.57-0.94, P=0.013).

Analysis of cervical cytology showed no difference between vaccinated and unvaccinated women with respect to atypical squamous cells of uncertain significance or low-grade squamous intraepithelial lesions (SIL). However, high-grade SIL, cervical carcinoma in situ, abnormal Pap findings, and conization/LEEP procedures all occurred significantly less often in vaccinated women (P<0.01 to P<0.001). Overall, HPV vaccination was associated with a 58% reduction in the odds ratio for all abnormalities found by Pap smear (95% CI 0.25-0.72).

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