Risk of anal cancer in HIV-infected and HIV-uninfected individuals in North America

Abstract

Background: Anal cancer is one of the most common cancers affecting individuals infected with human immunodeficiency virus (HIV), although few have evaluated rates separately for men who have sex with men (MSM), other men, and women. There are also conflicting data regarding calendar trends.

Methods: In a study involving 13 cohorts from North America with follow-up between 1996 and 2007, we compared anal cancer incidence rates among 34 189 HIV-infected (55% MSM, 19% other men, 26% women) and 114 260 HIV-uninfected individuals (90% men).

Results: Among men, the unadjusted anal cancer incidence rates per 100 000 person-years were 131 for HIV-infected MSM, 46 for other HIV-infected men, and 2 for HIV-uninfected men, corresponding to demographically adjusted rate ratios (RRs) of 80.3 (95% confidence interval [CI], 42.7-151.1) for HIV-infected MSM and 26.7 (95% CI, 11.5-61.7) for other HIV-infected men compared with HIV-uninfected men. HIV-infected women had an anal cancer rate of 30/100 000 person-years, and no cases were observed for HIV-uninfected women. In a multivariable Poisson regression model, among HIV-infected individuals, the risk was higher for MSM compared with other men (RR, 3.3; 95% CI, 1.8-6.0), but no difference was observed comparing women with other men (RR, 1.0; 95% CI, 0.5-2.2). In comparison with the period 2000-2003, HIV-infected individuals had an adjusted RR of 0.5 (95% CI, .3-.9) in 1996-1999 and 0.9 (95% CI, .6-1.2) in 2004-2007.

Conclusions: Anal cancer rates were substantially higher for HIV-infected MSM, other men, and women compared with HIV-uninfected individuals, suggesting a need for universal prevention efforts. Rates increased after the early antiretroviral therapy era and then plateaued.

Figure 1.

Cohort-specific anal cancer incidence rates by cohort-specific prevalence of men who have sex with men (MSM), North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD), years 1996–2007. Each point represents 1 of 13 cohorts contributing data. The line represents the results of the weighted linear regression model with an intercept of 28.3 cases per 100 000 person-years, and slope of 1.18 cases per 100 000 person years per 1% increase in cohort-specific prevalence of MSM.

Figure 2.

Anal cancer incidence rates by calendar era for human immunodeficiency virus infected men who have sex with men (MSM), other men, and women, North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD), years 1996–2007. Vertical lines are 95% confidence intervals. P values from the Poisson regression model compare rates by calendar era with 2000–2003 as reference. The global P value for comparison of rates across eras is based on the likelihood ratio statistic.