Introduction: The incidence of human papillomavirus (HPV)-associated anal cancer is high in homosexual men, especially in the HIV-positive, but an understanding of the epidemiology of HSIL, the presumed precursor is lacking. We aimed to determine the prevalence and risk factors for HSIL in a community-recruited cohort of homosexual men.
Methods: The Study for the Prevention of Anal Cancer (SPANC) is a three-year study investigating the natural history of anal HPV infection and associated lesions in homosexual men aged ≥35 years. At each visit all men receive an anal swab for cytology and HPV genotyping (Roche Linear Array), and high resolution anoscopy with biopsy of suspected lesions. Using composite diagnosis, anal HSIL was defined as having either intraepithelial neoplasia grade 2/3 on histology and/or possible HSIL/HSIL on cytology.
Results: 342 men were recruited by the end of March 2013. Median age was 49 and 28.7% were HIVpositive. Overall 68.7% of men had HPV-related anal abnormalities. Just under half (45.6%) of the men (50.0% of the HIV-positive and 43.9% of the HIV-negative, p=0.053) had HSIL. HSIL-AIN2 and HSIL-AIN3 were diagnosed in 17.0% and 28.7% of men respectively. HIV-positive men were more likely to have HSIL-AIN3 (p=0.053) than HIV-negative men. The prevalence of HSIL was significantly higher in men with detectable HPV16 or HPV18 DNA compared to those without (71.8% versus 30.9%, p<0.001). In multivariate analysis, HSIL was associated with HPV16 (p<0.001), HPV18 (p=0.017), history of anal warts (p=0.006), higher level of education (p=0.041), and current cigarette smoking (p=0.035).
Conclusion: The prevalence of HSIL was very high in this population. The strong associations with HPV16 and HPV18 suggest that universal vaccination of adolescent boys has enormous potential to prevent HPV-related morbidity among men in the future. Research is needed to help identify, and effectively treat those at highest risk of progressing to cancer.
