The ability to detect and treat pre-malignant anal lesions suggests screening may prevent anal cancer. The incidence of anal cancer in men who have sex with men (MSM) living with HIV exceeds that of cervical cancer before screening was introduced.
High-resolution anoscopy (HRA) with intervention for high-grade squamous intraepithelial lesions (HSILs) was offered to asymptomatic HIV-positive MSM. Patients with HSILs were treated and follow-up HRA performed after 6 months, whilst patients with low-grade squamous intraepithelial lesions had a repeat HRA after 12 months.
Three hundred and sixty-eight asymptomatic MSM had a total of 1497 HRAs during a median follow-up of 4.2 years (maximum 13 years). At first HRA, 36% had normal appearances, 16% had no dysplasia, 15% anal intraepithelial neoplasia (AIN)-1, 19% AIN-2 and 13% AIN-3. During follow-up, five patients (1.4%) developed invasive anal cancer (incidence 2.7 per 1000 person-years). The 5-year cancer rate for the 368 patients was 0.3% [95% confidence interval (CI) 0–0.6%]. Progression to cancer was associated with higher age (P = 0.049) and AIN-3 (P = 0.024). Ninety patients had AIN-3 present at least at one HRA. The cumulative risk of cancer from first AIN-3 diagnosis was 3.2% (95% CI 0–7.8%) at 5 years. One hundred and seventy-one patients had HSILs (AIN-2 or 3) present at least once. The cumulative risk of cancer from first HSIL diagnosis was 0.6% (95% CI 0–1.8%) at 5 years.
AIN-3 is a significant risk factor for subsequent anal cancer, although the tumours detected in screened patients were small localized, and generally the outcomes were favourable.