Objectives The incidence of anal cancer is increasing especially in HIV-positive men having sex with men. Screening for the cancer precursor, high-grade squamous intraepithelial lesions (HSIL), is challenging, as current treatment is suboptimal. The aim of this prospective study was to establish the efficacy of five consecutive days a week self-administered treatment with imiquimod 5% cream for both perianal and intra-anal HSIL and to assess the adverse effects and burden of this regimen.

Methods 44 patients with histologically proved perianal or intra-anal HSIL were treated with a five consecutive days a week imiquimod 5% cream regimen. When no response could be confirmed after the first 16 weeks of therapy, patients were encouraged to continue the use of the cream for a further 16 weeks. Side effects were routinely assessed.

Results Complete or partial response was observed in 20 (45%) of 44 patients with HSIL after 16 weeks of treatment; another nine patients showed complete or partial response after an additional 16 weeks of treatment, resulting in a response rate of 29 (66%) out of 44 patients.

Conclusions Topical imiquimod 5% cream is useful in HSIL. A five consecutive days treatment regimen with imiquimod 5% cream for HSIL does not seem to be more effective compared with the customary prescription for 3 days a week. A prolonged course of imiquimod 5% cream is warranted for intra-anal HSIL. Adverse effects are comparable between 3 and 5 days treatment regimen.