Outcomes reported in studies of anal high-grade squamous intraepithelial lesions treatments: systematic review.

Anal high-grade squamous intraepithelial lesion (HSIL) is a precursor of anal squamous cell carcinoma (ASCC). Reported outcomes from treatment trials vary widely, limiting understanding of the effectiveness of different interventions. This systematic review aimed to summarize the outcomes reported in studies evaluating treatments in anal HSIL. A systematic review of MEDLINE, Embase, CINAHL, and the Cochrane Library (inception to June 2025) was conducted. Eligible studies evaluated any anal HSIL treatment in any population. Verbatim outcomes and associated definitions, measurement tools, and timepoints were extracted and mapped to standardized outcome terms (SOTs), categorized using The Core Outcome Measures in Effectiveness Trials (COMET) Initiative taxonomy. Out of 5488 studies screened, 67 studies were included, comprising 40 observational studies, 23 interventional studies (5 randomized controlled trials), and 4 systematic reviews. A total of 966 outcomes were reported, grouped into 170 SOTs. Outcomes were mapped across all five COMET core areas (Death, Physiological/clinical, Life impact, Resource use, and Adverse events), with Physiological/clinical outcomes most frequently represented (131/170 SOTs; 77%). Substantial heterogeneity was observed, particularly in definitions of disease response, recurrence, and adverse events. For example, across 18 studies reporting 'complete response', definitions varied in assessment modality (clinical assessment alone, histology alone, cytology alone, or combined clinical-histological criteria), stringency (ranging from absence of visible lesions to absence of HSIL, LSIL, or any dysplasia), scope (lesion-specific versus field-wide assessment), and timing, which ranged from 3 weeks to 18 months post-treatment. Only three studies used validated patient-reported outcome measures (PROMs) for quality of life or functioning. Outcome reporting in anal HSIL treatment studies is highly inconsistent, limiting the synthesis of evidence and comparative analysis. These findings support the urgent need for a COS to standardize outcome selection and improve the quality and comparability of future trials.