The Effect on Outcomes of Using Fecal Immunochemical Tests (Fit) for Surveillance of Colorectal Adenoma Patients Within Miscan Micro-Simulation Evaluation

Background Surveillance colonoscopy for persons with colorectal-adenoma has become part of colorectal cancer (CRC) screening programs. Risk stratified recommendations vary, from surveillance colonoscopy at intervals of 12 months up to 10 years. Although no trials have reported on the efficacy of adenoma surveillance by fecal immunochemical testing (FIT), FIT demonstrated equivalence to colonoscopy in surveillance for interval cancers in other risk groups (e.g. family history of CRC) wherein FIT detected neoplasia sooner than scheduled surveillances. Methods To determine the value of FIT in the surveillance of post-polypectomy colorectal adenoma we used MISCAN micro-simulation modeling, based on published data for persons aged 50-75 years with low, intermediate and high-risk adenoma. Using 26 mutually exclusive surveillance programs configured within a model of biennial FIT based CRC screening, with calibrated diagnostic cut-off set at 100ng haemoglobin/mL(or 20μg/g stool); wherein individuals with positive screening tests receive a colonoscopy and those requiring polypectomy clearance are offered surveillance. Each simulation of 10-million entrants to screening with full adherence assessed differences in outputs relative to changes in surveillance offered. Surveillance colonoscopy strategies modeled included 1yr high risk, 3 yr intermediate and 5yr low risk intervals (as well as 3/3/10 & 3/5/10yrs) OR FIT surveillance at intervals of 0.5 - 2 years, stratified by risk-group. All strategies are compared to no surveillance (i.e. return to screening). Outcomes reported included quality-adjusted life-years gained (QALY), costs and cost/QALY. Results Modeled estimates demonstrated colonoscopy based surveillance at 1yr high-risk, 3 year intermediate and 5 yr low risk provided greatest QALY gain, compared with no surveillance (Figure). Strategies of 3/3/10 yr and 3/5/10 yr colonoscopy surveillance both offered lower QALY gain than a 1/3/5 yr combination. Whilst offering combined strategies of FIT & colonoscopy stratified to higher risk groups only, yielded greater QALY gain than by FIT alone, these strategies were subject to dominance; associated with higher net costs and lower QALYs than colonoscopy based surveillance. Sensitivity analyses included comparisons of the more sensitive 50ng haemoglobin /mL FIT cut-off level, whilst these improved outcomes relative to FIT100ng haemoglobin /mL they were not preferable to colonoscopy strategies. Conclusion Modeling suggests that colonoscopy- based surveillance following colorectal adenomatous adenoma polypectomy removal should be preferred to FIT-based surveillance based on current test performance. Funding: Health & Social Care Northern Ireland Public Health Agency/ National Cancer Institute and NIH/NCI Cancer Center Support Grant (P30 CA008748)