Evaluation of Anal Cancer Screening Among 18-to-34-Year-Old Men Who Have Sex With Men Living With HIV Over a 10-Year Period.

Background: Guidelines now support anal squamous cell carcinoma (ASCC) screening in men who have sex with men (MSM) living with HIV (LWH) aged ≥35 years. There is limited data on screening in MSM LWH <35 years. Setting: Two academic HIV clinics in the Northeastern US. Methods: We retrospectively evaluated all anal cytology and high-resolution anoscopy (HRA; referral criteria: atypical cells of undetermined significance [ASC-US] or worse cytology) performed for MSM LWH between ages 18-34 from 2013 to 2023. We evaluated risk factors for abnormal cytology or histology, and prevalence of high-grade dysplasia (HSIL) and ASCC. Results: Of 216 eligible MSM LWH, 111 (51%) were screened for ASCC at least once. Screened individuals had longer follow-up (median 4.0 vs 1.6 years) but were otherwise similar to unscreened individuals. Among 246 cytology tests, 19% were unsatisfactory and 31% abnormal, of which 1.2% reported HSIL. Of 23 HRAs following abnormal cytology, 10 (43%) revealed HSIL. Testing in response to symptoms was associated with abnormal results (OR 8.54; 95% CI 2.55-28.67). Human papillomavirus vaccination trended toward protection against abnormal results. We identified two cases of local ASCC, both in individuals with symptomatic condyloma and severe immunosuppression. Conclusions: Over 10 years, ASCC screening in MSM LWH <35 years was variable. Anal cytology had high unsatisfactory rates and poor correlation with histology. Despite high dysplasia prevalence among those undergoing HRA, ASCC was rare and diagnosed early from symptoms. Findings support excluding younger (≤34 years) MSM LWH from asymptomatic screening, and support symptom-driven testing to diagnose anal cancer early.