Multidisciplinary management of anal intraepithelial neoplasia and rate of progression to cancer: A retrospective cohort study.

Purpose: To describe the regional burden of AIN and rate of progression to cancer in patients managed in specialist and non-specialist clinic settings.

Methods: Patients with a histopathological diagnosis of AIN between 1994 and 2018 were retrospectively identified. Clinicopathological characteristics including high-risk status (chronic immunosuppressant use or HIV positive), number and type of biopsy (punch/excision) and histopathological findings were recorded. The relationship between clinicopathological characteristics and progression to cancer was assessed using logistic regression.

Results: Of 250 patients identified, 207 were eligible for inclusion: 144 from the specialist and 63 from the non-specialist clinic. Patients in the specialist clinic were younger (<40 years 31% vs 19%, p = 0.007), more likely to be male (34% vs 16%, p = 0.008) and HIV positive (15% vs 2%, p = 0.012). Patients in the non-specialist clinic were less likely to have AIN3 on initial pathology (68% vs 79%, p = 0.074) and were more often followed up for less than 36 months (46% vs 28%, p = 0.134). The rate of progression to cancer was 17% in the whole cohort (20% vs 10%, p = 0.061). On multivariate analysis, increasing age (OR 3.02, 95%CI 1.58-5.78, p < 0.001), high risk status (OR 3.53, 95% CI 1.43-8.74, p = 0.006) and increasing number of excisions (OR 4.88, 95%CI 2.15-11.07, p < 0.001) were related to progression to cancer.

Conclusion: The specialist clinic provides a structured approach to the follow up of high-risk status patients with AIN. Frequent monitoring with specialist assessments including high resolution anoscopy in a higher volume clinic are required due to the increased risk of progression to anal cancer.