Abstract
BACKGROUND: Anal cancer risk is elevated among people with HIV. Recent anal cancer incidence patterns among people with HIV in the United States and Canada remain unclear. It is unknown how the incidence patterns may evolve. METHODS: Using data from the North American AIDS Cohort Collaboration on Research and Design, we investigated absolute anal cancer incidence and incidence trends nationally in the United States and Canada and in different US regions. We further estimated relative risk compared with people without HIV, relative risk among various subgroups, and projected future anal cancer burden among American people with HIV. RESULTS: Between 2001 and 2016 in the United States, age-standardized anal cancer incidence declined 2.2% per year (95% confidence interval = ‒4.4% to ‒0.1%), particularly in the Western region (‒3.8% per year, 95% confidence interval = ‒6.5% to ‒0.9%). In Canada, incidence remained stable. Considerable geographic variation in risk was observed by US regions (eg, more than 4-fold risk in the Midwest and Southeast compared with the Northeast among men who have sex with men who have HIV). Anal cancer risk increased with a decrease in nadir CD4 cell count and was elevated among those individuals with opportunistic illnesses. Anal cancer burden among American people with HIV is expected to decrease through 2035, but more than 70% of cases will continue to occur in men who have sex with men who have HIV and in people with AIDS. CONCLUSION: Geographic variation in anal cancer risk and trends may reflect underlying differences in screening practices and HIV epidemic. Men who have sex with men who have HIV and people with prior AIDS diagnoses will continue to bear the highest anal cancer burden, highlighting the importance of precision prevention.