Invited commentary: Biological and clinical insights from epidemiologic research into HIV, HPV, and anal cancer.

Anal cancer is common among people infected with human immunodeficiency virus (HIV). This cancer is caused by human papillomavirus, and immunosuppression likely contributes to its development. In this issue of the Journal, Bertisch et al. (Am J Epidemiol. 2013;178(6):877-884) present the results of a case-control study of anal cancer among HIV-infected people in Switzerland. They demonstrate that anal cancer risk is increased in association with a low CD4+ cell count (a clinical measurement of immune status). In particular, HIV-induced immunosuppression was most severe among cases approximately 6-7 years prior to the diagnosis of anal cancer. A plausible biological interpretation is that immunosuppression is important at an early stage of the development of anal cancer, but that the neoplastic process becomes irreversible over time with persistent human papillomavirus infection and genetic damage. With current efforts to provide earlier combination antiretroviral therapy to HIV-infected people, anal cancer incidence may start to decline. Bertisch et al. also demonstrate a strong association between serum antibodies against the human papillomavirus type 16 protein E6 and anal cancer risk, highlighting the role of this viral oncoprotein in carcinogenesis. Additional biomarkers could help refine clinical approaches to anal cancer screening and prevention for the HIV-infected population.