Incidence and burden of anal cancer-time to fight the growing disparities

Anal cancer (AC) is rare, but its incidence is increasing, although at different rates across countries and population groups. The increase in AC incidence is primarily due to the increased prevalence of human papillomavirus (HPV), which causes 90% of squamous-cell carcinoma (SCC), the most common AC histology subtype. Understanding estimates of incidence across countries and risk groups is essential for estimating future disease burden and predicting cancer care resource allocation. In this review, we summarize the latest literature with an emphasis on global disparities and challenges in AC prevention. Globally in 2020, >30 000 people were diagnosed with anal SCC, with two-thirds of cases occurring in North America and Europe. AC incidence varies greatly between population groups; higher incidence is associated with older age, females, anal sexual intercourse, immunosuppression [particularly people living with human immunodeficiency virus (HIV) and solid organ transplant recipients], and prior HPV-related gynecologic (pre-)cancers. Primary prevention of AC relies on preventing HPV infection by vaccination and secondary prevention relies on screening and treatment of high-grade squamous intraepithelial lesions (HSILs). Globally, there are considerable disparities in AC. While its incidence is currently highest in high-income countries, it is expected to increase in low-income countries (LICs) in the future, due to higher HPV prevalence and lower HPV vaccine coverage. Continued effort is essential to gather data on prevalence and incidence, especially in LICs, to strengthen vaccination programs globally and to promote research networks around the world for better evidence on screening and treatment.