Routine screening of anal cytology in HIV-infected subjects and the impact on invasive anal cancer. A prospective cohort study.

BACKGROUND: The efficacy of screening programs to prevent anal cancer in HIV-1-infected subjects is unclear.

AIM: To examine the impact of a screening program to detect anal cancer precursors on the incidence of cases of invasive-anal-squamous-cell-carcinoma (IASCC) in HIV-1-infected subjects.

PATIENTS AND METHODS: Single-center, retrospective analysis of a prospective cohort of HIV-1-infected outpatients attending a reference HIV Unit from January 2005 onward. All participants were invited to participate in a continued structured screening program for anal cancer prevention. We estimated the incidence of IASCC and performed a comparative analysis between subjects enrolled in the screening program (screening group) and those who declined to participate (non-screening group). To reduce any selection bias, a propensity score analysis was applied.

RESULTS: 3111 HIV-1-infected subjects [1596 men-who-have-sex-with-men (MSM), 888 men-who-have-sex-with-women (MSW), 627 women] were included (mean age 41 years), median follow-up 4.7 years (14,595 patient/years of follow-up). Of them, 1691 (54%) participated in the screening program. Ten patients were diagnosed with IASCC: two of them (MSM) in the screening group and eight (4 MSM, 2 MSW and 2 women) in the non-screening one. The incidence rate of IASCC was 21.9 (95%CI:2.7-70.3) and 107.0 (95%CI:46.2-202.0) per 100,000 person-years, respectively. After a propensity score adjustment, the difference was significant in favour to the screening group (HR:0.17, 95%CI:0.03-0.86).

CONCLUSIONS: The number of cases of IASCC was significantly lower in HIV-infected subjects engaged in an anal cytology screening program. These results should be validated in a randomized clinical trial.