Impact of the HIV Epidemic on the Incidence Rates of Anal Cancer in the United States

The risk of anal cancer is substantially increased in HIV-infected individuals. Thus, the HIV epidemic may have influenced the increasing anal cancer trends in the United States. We estimated the impact of the HIV epidemic on trends in anal cancer incidence in the United States during 19802005. Data on anal cancer cases with and without AIDS were obtained from the HIV/AIDS Cancer Match Study. The number of HIV-infected anal cancer cases without AIDS was estimated from the number of anal cancers occurring before diagnosis of AIDS. The proportion of anal cancer cases with HIV infection in the general population was calculated. We estimated temporal trends in the incidence rates of anal cancer in the general population overall and after exclusion of HIV-infected cancer cases by calculating annual percent changes and 95% confidence intervals (CIs) using a Joinpoint log-linear model. All incidence rates were standardized to the 2000 US population by age, sex, and race. During 19802005, of the 20 533 estimated anal cancer cases, 1665 (8.1%) were HIV-infected. During 20012005, the proportion of anal cancer cases with HIV infection was the highest1.2% (95% CI 0.93 to 1.4%) among females and 28.4% (95% CI 26.6 to 29.4%) among males. During 19802005, HIV infection did not have an impact on the trends in anal cancer among females (incidence rates increased by 3.3% [95% CI 3.0 to 3.7%] annually overall, and by 3.3% [95% CI 2.9 to 3.6%] annually without HIV-infected anal cancer cases) but had a strong impact on the trends in anal cancer among males (incidence rates increased by 3.4% [95% CI 2.9 to 3.9%] annually overall, and by 1.7% [95% CI 1.2 to 2.3%] annually without HIV infection). During 19802005, the increasing anal cancer incidence rates in the United States were strongly influenced by the HIV epidemic in males but were independent of HIV infection in females.