International trends in anal cancer incidence rates

Background: Previous studies have reported rapid increases in anal cancer incidence rates in seven high-income countries in North America, Europe and Oceania. There is very limited information on whether this pattern is replicated in other parts of the world. In this study, we examine recent trends in anal cancer incidence in 18 countries worldwide. Methods: We calculated age-standardized incidence rates for anal squamous cell carcinoma (ASCC) and anal adenocarcinoma (AAC) for a minimum of 13 years through to 2007, using data from the International Agency for Research on Cancer's Cancer Incidence in Five Continents series, and applied joinpoint regression models to assess changes in incidence rates. We also conducted an extended analysis of the data from the USA through to 2012. Results: ASCC was the main histological subtype in most of the countries considered in this analysis. The incidence of ASCC increased in both men and women in several high-income countries, including Australia, Canada, Denmark, France, Italy, Netherlands, the UK and the USA, whereas it increased only in women in Colombia, Estonia, the Russian Federation, Slovakia and Switzerland. Conversely, there was little change in the incidence of ASCC in either men or women in India, Israel, Japan, Singapore and Spain. The incidence rates of AAC decreased or were stable in most populations. Conclusions: The ASCC incidence rates increased in both men and women or in women in all countries included in this study, except Asian countries and Spain, where the rates remained unchanged. Population-based preventive measures, including human papillomavirus vaccination and advocacy for safe sexual behaviours, may contribute to curbing the surging burden of the disease.