Anal squamous intraepithelial lesions (aSIL) in HIV-positive MSM : incidence and risk factors of aSIL, and of progression and clearance of low-grade aSIL

BACKGROUND: HIV-positive men who have sex with men (MSM) are at risk for developing anal squamous cell carcinoma. Data on the natural history of the precursor, anal squamous intraepithelial lesions (SIL), are limited. METHODS: HIV-positive MSM were screened for histopathological SIL by high resolution anoscopy. For participants without SIL at baseline we estimated the cumulative incidence and risk factors of SIL. For participants with low-grade SIL (LSIL) at baseline, risk of progression to high-grade SIL (HSIL) and the clearance rate were estimated at lesion level. RESULTS: Of 807 men without SIL at baseline, 107 had a second HRA between 1-4.5 years. At the second visit 18 men (16.8%) showed LSIL, and 25 (23.4%) HSIL. Age was associated with incident LSIL (adjusted odds ratio (aOR) 2.10 per 10 year older, p=0.012). Of 393 men with LSIL at baseline, 114 had a second HRA between 0.5-2.5 years. Eighty-seven (49.2%) of the 177 LSIL lesions found at baseline had cleared at the second visit; 29 (16.4%) had progressed to HSIL. CONCLUSION: Incident LSIL and HSIL were common during follow-up among HIV-positive MSM without dysplasia at baseline. Among men with LSIL at baseline, nearly half of these lesions cleared, while a small portion progressed.