Anal intraepithelial neoplasia--is treatment better than observation?

Anal Intraepithelial Neoplasia (AIN) is an increasingly common condition for which the best treatment has not been well established. Traditional management was based on a 'watch and wait' strategy, but as the natural history of AIN and its progression to anal cancer is becoming better understood, more active treatment strategies are warranted. A best evidence topic in surgery was written according to a structured protocol to address the question whether treatment is indicated in patients with AIN. A total of 169 papers were identified using the defined search criteria. This included only one randomised controlled trial. Case series were therefore also included to help answer the question. The details of the papers were tabulated including relevant outcomes and study weaknesses. We conclude that treatment of high grade AIN, particularly in high risk groups is recommended to try to avoid progression to anal cancer. Treatment options that have shown some benefit include topical use of imiquimod cream or ablation directed by high resolution anoscopy.