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High-risk anal HPV infections persist in a significant proportion of HIV-negative MSM
Michael Carter, 2016-03-30 06:50:00
Anal infection with human papillomavirus (HPV) types associated with a high risk of pre-cancerous and cancerous cell changes persisted for two years in 37% of men who have sex with men (MSM) enrolled in an international study published in Clinical Infectious Diseases. The prospective, observational study involved 406 HIV-negative MSM recruited in Brazil, Mexico and the United States. Among men with prevalent high-risk HPV infection, 37% retained the infection for at least 24 months and HPV-16 infection for at least 24 months in 30% of those with this infection at baseline.
“Slightly over one-third of MSM exhibited persistence of prevalence high-risk types for > 24 months indicating that prevalent high-risk anal HPV infection may be a clinically important event,” comment the investigators. “These results may help inform future anal cancer screening that uses HPV-DNA testing.”
Incidence of anal cancer is especially high among MSM. Vaccines are available that provide excellent protection against infection with the HPV types especially associated with pre-cancerous and cancerous anal cell changes. However, access to such vaccination is limited in most healthcare settings. Information is therefore needed to inform programmes screening for anal infection with high-risk HPV types and/or suspicious anal cell changes.
Investigators from the HPV Infection in Men (HIM) Study therefore designed a sub-study restricted to MSM. At baseline and at intervals every six months, participants had anal swabs which were tested for HPV infection and 13 high-risk genotypes. Only HIV-negative men were eligible for inclusion in the study.
A total of 406 were recruited and 82% were retained over the five study visits. Most of the men (n = 336) reported sex with men and women (MSWM) and 70 reported sex with men only (MSOM). The median period of follow-up was two years.
There was no significant difference in the persistence of HPV infection between MSWM and MSOM (8.8 vs. 6.0 months, respectively). The two groups were therefore combined in subsequent analysis.
The median duration of prevalent infection differed according to genotype, ranging between 14 and 27 months. Incident infections, however, were of much shorter duration. For example the median duration of HPV-16 infection was seven months.
Of the 106 men with high-risk infection at baseline, 37% retained this infection for at least 24 months, with 30% of men with prevalent HPV-16 infection at baseline retained the infection for a similar period.
An analysis that controlled for potential confounders showed that men reporting 20 or more lifetime anal sex partners, and also those with one or more anal sex partner in the previous three months, were over twice as likely to have persistent high-risk infection than men with fewer partners (PR = 2.06; 95% CI, 1.07-3.97).
However, men with the highest number of lifetime female partners were 71% less likely to have persistent infections compared to men reporting between zero and two lifetime female partners.
“These data not only support development of anal pre-cancer screening policy, but also appropriate counselling for MSM who have prevalent vs. incident infection at the anal canal,” conclude the authors. “These results may also inform debates in countries considering vaccination for males by informing anal HPV natural history modelling.”
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