EP574 - Predictors of Anal High-Grade Intraepithelial Lesion Clearance After Fulguration: A Single-Institution Retrospective Study

Purpose/Background: Patients living with human immunodeficiency virus (HIV) have an increased prevalence and incidence of anal human papillomavirus infections and high-grade squamous intraepithelial lesions (HSIL). High-resolution anoscopy (HRA) and treatment of HSIL with fulguration reduces the risk of progression to squamous cell carcinoma (SCC). However, limited data exists on clinical and demographic factors that may be associated with HSIL clearance after treatment. This study describes a single institution's experience with treatment of HSIL and identifies predictors of clearance.

Methods/Interventions: We conducted a retrospective review of patients participating in surveillance of anal intraepithelial lesions from September 2018 to July 2025 who had biopsy-proven HSIL, underwent office-based or operative HRA with fulguration and had at least one follow-up visit. HSIL clearance was defined as patients who had a normal anal Pap smear, normal HRA or benign biopsy at follow-up. Patient clinical characteristics including age, sex, race, insurance type, HIV status, smoking history, fulguration location, extent fulguration of anal canal and recurrence, among other factors, were recorded. Extent of fulguration was estimated when necessary from operative notes. Statistical analysis was performed using chi-squared and logistic regression tests in Jamovi.

Results/Outcomes: Of 1,296 patients who participated in surveillance of anal dysplasia, only 220 met the inclusion criteria. The cohort was predominantly male (94%) and HIV-positive (71%) with 59% having no smoking history. Median follow-up was 946.5 days (Interquartile range, IQR: 568.8-1481.8), and 61% achieved HSIL clearance which on average took 779.1 days after about 2 separate fulgurations (IQR: 1-2). Recurrence occurred in 22% of patients after an average of 554.5 days. Most patients underwent office-based fulguration (64%), regardless of clearance status. Clearance patients underwent more total fulgurations (253 vs 162) but had significantly lower average extent of fulgurations per visit (26.3% vs 32.9% of anal canal, p = 0.023) and longer follow-up durations (1167 days vs 874 days (p < 0.001). One patient progressed to SCC in situ. There were no statistically significant differences between those with and without clearance for age, sex, race, ethnicity, language, insurance, HIV status or smoking history, although former smokers were more common in the clearance group (32.1% vs 24.4%).

Conclusion/Discussion: Patients achieving HSIL clearance had longer follow-up and underwent more treatment sessions, emphasizing the importance of continued surveillance in this population to mitigate the risk of SCC. Those with clearance required less extensive fulgurations, suggesting that some patients may have a less aggressive or more localized disease process in the anal canal. While no demographic or social risk factors were clearly associated with clearance in this population, the data suggests that quitting smoking may be predictive of clearance. Patients undergoing surveillance and treatment of HSIL will likely benefit from routine counseling on smoking cessation. This study is limited by sample size, estimates used to calculate the extent of anal canal fulguration, and lack of data regarding marijuana smoking history. Further research is needed to clarify predictors of HSIL clearance following treatment.

Factors associated with clearance of anal high-grade intraepithelial lesions