Background: The incidence of anal cancer, a Human Papillomavirus (HPV)-related neoplasia, has been increasing in recent decades, mainly in men who have sex with men (MSM). Cytological changes of the anal epithelium induced by HPV can be detected through an anal pap smear. This study aimed to evaluate the prevalence and epidemiological correlates of anal cytological abnormalities among relatively young MSM at risk for HIV-1 infection, to help clarify whether or not this population deserves further investigation to assess the presence of anal cancer precursor lesions.
Methods: MSM were recruited among attendees of a large STI clinic for a HIV-1 screening program. Anal samples, collected with a Dracon swab in PreservCyt, were used both for liquid-based cytology and HPV testing by the Linear Array HPV Genotyping Test. Data regarding socio-demographic characteristics and sexual behavior were collected in face-to-face interviews.
Results: A total of 346 MSM were recruited (median age 32 years). Overall, 72.5% of the individuals had an anal HPV infection, with 56.1% of them being infected by oncogenic HPV genotypes. Anal cytological abnormalities were found in 29.8% of the cases (16.7% ASC-US and 13.1% L-SIL). Presence of ASC-US+ was strongly associated with infection by any HPV type (OR = 4.21, 95% CI: 1.97-9.23), and particularly by HPV 16 and/or 18 (OR = 5.62, 95% CI: 2.33-13.81). A higher proportion of ASC-US+ was found in older MSM, in those with a higher number of lifetime partners and in those with a history of ano-genital warts. However, none of these variables or the others analyzed showed any significant association with abnormal cytological findings.
Conclusions: The presence of anal cytological abnormalities in about one third of the recruited MSM and their strong association with HPV infection, in particular that caused by HPV 16 and/or 18, might provide a further complement to the data that now support the introduction of HPV vaccination among MSM to protect them from the development of HPV-associated diseases. Additional studies are needed to determine whether and how screening for anal cancer precursor lesions should be performed in younger MSM.