July 10, 2008
 Preliminary research by University of Arizona scientists at the Mel and Enid Zuckerman College of Public Health suggests that almost 25% of heterosexual men test positive for a virus linked to cervical cancer in women, a surprisingly high percentage. The effects of the human papillomavirus, or HPV, are well documented in women; this study shows that sexually-active heterosexual men may be more likely to have anal HPV than was previously realized. The results might raise important issues about the prevalence and risk factors for anal HPV — the primary cause of anal cancer; further studies that assess the persistence of anal HPV in heterosexual men are needed to explore this.
 The analysis of anal HPV in heterosexual men was led by Alan Nyitray, upper left, a PhD student and research scientist in the UA Zuckerman College’s Epidemiology and Biostatistics Division. Robin Harris, PhD, MPH, an Associate Professor at the University of Arizona Mel and Enid Zuckerman College of Public Health (MEZCOPH), right, is the principal investigator. The results, published in June in the Journal of Infectious Diseases, looked at anal human papillomavirus (HPV) in heterosexual men.
Behavioral data and anal biological specimens were collected from 253 men in Tucson and Tampa, Fla., who acknowledged having engaged in sexual intercourse with a woman during the preceding year. On the basis of DNA analysis, the overall prevalence of anal HPV infection was found to be 24.8 percent in the 222 men who said they had never had sexual intercourse with men. These results suggest that anal HPV infection may be more common in heterosexual men that previously thought.
Former studies of husbands of women with confirmed HPV yielded 8% (Brazil study of husbands of women with confirmed HPV) and 1.2% (Amsterdam study of heterosexual men attending an STD clinic) anal HPV prevalences in heterosexual men. The differences in study results could be due to: 1) the tests today are much more sensitive and can detect minute levels of the virus that old tests could not, and 2) the sampling of two anal sites: the anal canal, and the perianal region 1-2 cm outside the anus. For the anal canal, the prevalence was 16.6%, double the Brazilian prevalence.
Risk Factors
According to National Cancer Institute data, anal cancer in men nearly tripled between 1973 and 2005, and the Insititute estimates that 2,020 men will be diagnosed with — and 250 men will die of — anal cancer in 2008. Most increases have been known to be among men who have sex with men, and people who have HIV (both men and women). The incidence of anal cancer in gay men is higher than the incidence of cervical cancer in women.
The link between HPV and cervical cancer in women led to the development of a preventative vaccine for women; no similar vaccine has been released for men but one is being tested, the Centers for Disease Control and Prevention reports. "This is important for helping us understand whether the vaccine might have some potential use in men, too," said Mr. Nyitray.
HPV is a transitory virus, which means that typically there are no symptoms and the body usually clears the virus on its own. In the general population, 80% or more of us will have HPV at least once in our lives. For anal HPV in women, only one study has been performed and it found that 27% of the subjects tested positive, similar to the men’s results in this paper. People who do not clear HPV are the ones who are at risk for cervical, anal, or other associated types of cancer, Nyitray said.
Risk factors independently associated with anal HPV were a man’s total number of female sex partners; those who tested positive were more likely to have higher total number of lifetime female sexual partners, and a frequency of sex with females of 2-4 times in the previous month. Nyitray says it is unclear why men with a lower and higher frequency of sex with females than 2-4 times in the month were at lower risk. He says it’s possible that men with a lower frequency of sex were more likely to be single instead of married. Those who tested positive were more likely to be less than or equal to 30 years of age, also. Of the men with anal HPV infection, 33.3 percent had at least one of 13 oncogenic HPV types, which are the types that may lead to cancer.
Further Studies
Researchers at The University of Arizona Mel and Enid Zuckerman College of Public Health, Arizona Cancer Center, and the H. Lee Moffitt Cancer Center and Research Institute in Tampa collaborated on the study, which now needs to be confirmed in other populations of heterosexual men. Mr. Nyitray has obtained an R03 grant from the National Cancer Institute to fund these further studies of samples from a larger group of men from the United States, Mexico and Brazil. The R03 grant is an ancillary study to an NIH-funded study led by Dr. Anna Giuliano at the Moffitt Cancer Center.
This study was sponsored by the Centers for Disease Control and Prevention through the Association of American Medical Colleges.
Please send comments and corrections for this web page to Loretta McKibben.
Corrections and revisions added on July 18, 2008.
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