Effectiveness of topical cidofovir for treatment of refractory anal high-grade squamous intraepithelial lesion

Ablative electrocautery is effective treating anal high-grade squamous intraepithelial lesions (HSILs). However, persistence or recurrence of the HSIL despite ablative sessions is not uncommon. The aim of this study is to assess the feasibility of topical cidofovir as salvage therapy for the management of refractory HSIL. A prospective uncontrolled unicenter study of men and transgender people who have sex with men with HIV who had a refractory intra-anal HSIL after ablative treatments and who received topical cidofovir (ointment at 1%, auto-applicated, three times a week, a total of 8 weeks) as salvage therapy. Effectiveness was evaluated on-treatment defining response as resolution or regression to low-grade lesion of HSIL in the biopsy posttreatment. Tolerance and recurrences were recorded. From 2017 to 2022, 23 patients with refractory intra-anal HSIL (78.3% persistent lesions, 39% affecting > 50% of circumference, and a median of six previous ablative sessions) were treated with topical cidofovir. A response was observed in 16 of 23 patients [69.5% (95% confidence interval (95% CI) 50.8-88.4)]. Local tolerance was reported as regular or bad in 13 patients (52.2%), requiring modification of the treatment in eight patients (three early discontinuation and five dose reduction). Non-serious side effects were reported. After a median follow-up of 30.3 months, two of the 16 patients with a response developed recurrent HSIL [recurrence rate, 25.4% at 12 months (95% CI, 0-35)]. Topical cidofovir could be a good option in the management of anal HSIL due to its good effectiveness, low recurrence rate, and acceptable tolerance even in difficult-to-treat lesions.