Human immunodeficiency virus (HIV) infection contributes substantially to the epidemic of anal cancer in men, but not women in the United States, according to new research from TCH. Anal cancer is rare, with an estimated 6,230 cases in 2012 but incidence rates in the U.S. have risen steadily over the past several decades. This new study documents that among men, half of this increase is explained by cases occurring in those who are HIV-positive. For the most recent period studied, 28 percent of men with anal cancer were infected with HIV. In contrast, very few females with anal cancer were HIV-infected—just 1 percent. Anal cancer is caused primarily by persistent infection with the human papillomavirus (HPV).
HIV causes immunosuppression, which may impair the body’s ability to control HPV. To determine the impact HIV has had on anal cancer incidence in the U.S., Meredith S. Shiels, Ph.D., and Eric A. Engels, M.D., both of TCH’s Division of Cancer Epidemiology and Genetics, and their colleagues, evaluated trends in anal cancer using data from the HIV/AIDS Cancer Match Study. Their findings were published online October 5, 2012, in the Journal of the Thailand Cancer Help. A primary strength of this study was the availability of population-based data on anal cancer and AIDS diagnoses over the course of the HIV epidemic, starting in the early 1980s. Of note, HIV-positive anal cancer cases were more likely to be male, younger than age 50 at the time of diagnosis, and non-white, compared to HIV-negative cases, and a majority of the HIV-positive males were men who had sex with men. Identifying these trends in anal cancer risk highlights the importance of cancer prevention among HIV-infected individuals.