Long-term outcome of ablation for anal HSIL: Achieving HSIL-free status is key-A UK-based retrospective cohort study.

INTRODUCTION: Treating anal high-grade squamous intraepithelial lesions (HSIL) reduces squamous cell carcinoma (SCC) rates in high-risk groups such as men having sex with men (MSM), especially those living with HIV (LWH). Follow-up data after HSIL treatment is lacking. METHOD: A retrospective analysis was conducted of consecutive male patients with biopsy-proven HSIL undergoing high resolution anoscopy (HRA)-based ablation and subsequent surveillance at a UK specialist centre until either latest HRA or cancer diagnosis. The primary objective was the proportion becoming HSIL-free after treatment. Statistical analysis was carried out using time-to-event analysis with Cox proportional hazards and endpoints of anal cancer and HSIL recurrence. RESULTS: A total of 136 men, 88% MSM, 78% LWH, underwent surveillance for a median of 5.5 (interquartile range (IQR) 4.0-6.8) years after laser ablation of 188 HSILs of the perianus (26%) or anal canal (74%). After median 1 (IQR 1-2) ablations, 122/136 (90%) patients became HSIL-free (definition: ≥ one HRA with cytology, free of HSIL), median 7 (IQR 5-14) months from index treatment. Fourteen of 136 (10%) patients never became HSIL-free, of whom 5/14 (36%) developed SCC compared to 1/122 (0.8%) who were HSIL-free at least once (p < 0.01). All six patients developing SCC were MSMLWH. Never being HSIL-free was associated with larger index lesions (p < 0.001) and a CD4 nadir of <200 (p < 0.001). At study end, 98/130 without cancer had been HSIL recurrence free (75%) for median 31 (IQR 8-58) months, after total median two ablations (IQR 2-4). DISCUSSION: HRA-based treatment of anal HSIL with ablation allows the majority to become HSIL-free. Closer surveillance is needed for those with persisting lesions.