777    

Background:  HIV-infected persons are at increased risk for some types of cancer. Anorectal cancer may be curable if diagnosed early. Rates of anorectal cancer in the general population are low, but increased ARC rates in HIV-infected persons have been reported in case series and in limited cohorts. We analyzed data from a large cohort of persons with HIV to determine if anorectal cancer rates are higher than in the general population, and to identify factors associated with incident anorectal cancer.

Methods:  We used data from a large observational cohort study (the Adult/Adolescent Spectrum of HIV Disease project), to calculate rates of anorectal cancer diagnoses from 1990 to 2002, and used logistic regression to determine whether age, sex, CD4 cell count, stage of HIV disease, or risk for HIV infection were associated with incident anorectal cancer. For comparison, we calculated ARC rates in a general population cohort from 1992 to 2000 using data from the NCI’s Surveillance, Epidemiology, and End Results (SEER)-12 public-use dataset. We standardized ASD anorectal cancer rates on age, and on age and sex, to a standard population from the SEER data.

Results:  Among 58,039 HIV-infected persons, 150 were documented as having anorectal cancer and contributed 231,450 person-years of follow-up. Among persons with anorectal cancer in ASD, 92% were male, 44% were aged 35 to 44 years, and 79% were exposed to HIV through male-male sex. The age-standardized anorectal cancer rate among the HIV-infected persons was 84.9 cases per 100,000 person-years (95% CI:  52.4 to 117.5); the age- and sex-standardized rate was 66.1 per 100,000 person-years (CI:  38.0 to 94.2). The general population rate was 21.8 per 100,000 person-years (CI:  21.6 to 22.0). Incidence of anorectal cancer was associated with exposure to HIV through male-male sex (vs male-female sex; adjusted odds ratio [AOR]: 5.6, CI:  1.8 to 17.3); age ≥ 45 years (AOR: 2.5, CI:  1.6 to 3.9) and 35 to 44 years (AOR:  1.7, CI:  1.1 to 2.5) versus age <35 years; clinical AIDS diagnosis (AOR: 1.5, CI:  1.1 to 2.2); and CD4 count <200 (AOR: 4.0, CI:  1.9 to 8.4) or 200 to 499 (AOR: 2.4, CI:  1.1 to 5.1) vs CD4 ≥500.

Conclusions:  Persons with HIV infection are at substantially increased risk for anorectal cancer compared with the general population. In this cohort, anorectal cancer was associated with male-male sex, greater age, and more advanced HIV disease. These data suggest that clinicians must be vigilant for ARC during periodic examinations of HIV-infected persons, especially men with a history of male-male sex, older persons, and those at more advanced stages of disease.

Keywords: anorectal cancer; epidemiology; opportunistic illness