QS137 - A Thousand Cuts: Clinical and Socioeconomic Modeling of Anal Dysplasia Screening Practices

Purpose/Background: Findings from randomized clinical trials suggest that screening and treating anal dysplasia in HIV-positive patients prevents anal cancer. However, the optimal approach of who to screen remains uncertain. Annual screening with reflex high resolution anoscopy (HRA) for all at-risk patients risks overburdening patients and backlogging anal dysplasia care pathways. The purpose of this study was to identify the optimal approach to anal dysplasia screening that would maximize quality-adjusted life expectancy and minimize healthcare costs.

Methods/Interventions: We designed a Markov model that included a hypothetical cohort of 2000 patients, representing the average patient living with HIV in the United States, with varying degrees of anal dysplasia. We assigned patients in a 1:1: fashion to anal dysplasia screening with annual anal pap and reflexive HRA versus no screening. Regardless of screening strategy, patients were assigned a 2% annual risk of developing low-grade squamous intraepithelial lesions (LSIL) and a 2% annual risk of progressing to high grade squamous intraepithelial lesions (HSIL), if LSIL present in the prior year. Patients with HSIL who were not receiving annual screening were estimated to have a 4% annualized chance of developing anal cancer while patients who were receiving annual screening and reflex treatment were assigned a 2% chance. Patients receiving annual screening with no anal dysplasia or LSIL were assigned a 0.01 QALY decrement for biopsies alone while patients with HSIL were assigned a 0.04 QALY decrement for both biopsies and ablation. The annual costs associated with screenings were $1,119 for HRA biopsies alone and $1,992 for both biopsies and ablation. The discounted costs and QALYs after cancer diagnosis were assumed to be the same in both groups. We also performed a subgroup analysis in a selective high-risk population of patients aged 35 and older with HIV infection. The model was informed by published studies and expert opinion.

Results/Outcomes: When accounting for costs and benefits, the no-screening strategy dominated the screening for anal dysplasia strategy as it generated more quality adjusted life years (50.1 QALYs versus 49.9 QALYs) and reduced total costs of care by $24,872 per patient. When examining high-risk individuals, where most patients in the model had biospy-proven HSIL at baseline, the screening group generated more quality adjusted life years (49.0 QALYs versus 48.4 QALYs) but resulted in more than double the cost per patient compared to the no screening group ($58,147 versus $25,683; ICER = $54,107 per QALY).

Conclusion/Discussion: Screening for anal dysplasia offers an important clinical benefit to high-risk individuals, but targeted populations for screening defined by current guidelines likely overpromote its use with increased patient harm and societal costs. More restrictive screening strategies would produce a more favorable population-wide benefit.