Is screening for anal cancer warranted in homosexual men?

Some investigators have proposed screening homosexual men for anal cancer and its probable precursor, high grade anal intraepithelial neoplasia (AIN). Using widely accepted criteria for the introduction of screening programmes, this paper reviews the current evidence for screening for this condition in this high risk population and highlights areas where additional research is required. While it is accepted that the incidence of anal cancer is at least 20 times higher in homosexual men than the general population, the natural history of anal cancer and its precise relationship with AIN is not clearly understood. Anal intraepithelial neoplasia is a very highly prevalent disease among homosexual men, but little is known about what predicts progression to invasive disease. The screening tests, exfoliate cytology and high resolution anoscopy, have a sensitivity of between 45 and 70%. Treatment options for AIN are limited by morbidity and high recurrence rates and there are no randomised controlled trials studying the efficacy of therapeutic agents or surgery for high grade AIN, although immunotherapies show very early promise. Theoretically, early detection may lead to better treatment outcomes. Studies of the potential negative consequences of screening programmes on the homosexual population are needed. The currently available data does not support the implementation of a screening programme for AIN and anal cancer in homosexual men in Australia.