Fendrick, A. Mark

Abstract Colorectal cancer–screening models commonly assume 100% adherence, which is inconsistent with real-world experience. The influence of adherence to initial stool-based screening [fecal immunochemical test (FIT), multitarget stool DNA (mt-sDNA)] and follow-up colonoscopy (after a positive stool test) on colorectal cancer outcomes was modeled using the Colorectal Cancer and Adenoma Incidence and Mortality Microsimulation Model. Average-risk individuals without diagnosed colorectal cancer at age 40 undergoing annual FIT or triennial mt-sDNA screening from ages 50 to 75 were simulated. Primary analyses incorporated published mt-sDNA (71%) or FIT (43%) screening adherence, with follow-up colonoscopy adherence ranging from 40% to 100%. Secondary analyses simulated 100% adherence for stool-based screening and colonoscopy follow-up (S1), published adherence for stool-based screening with 100% adherence to colonoscopy follow-up (S2), and published adherence for both stool-based screening and colonoscopy follow-up after positive mt-sDNA (73%) or FIT (47%; S3). Outcomes were life-years gained (LYG) and colorectal cancer incidence and mortality reductions (per 1,000 individuals) versus no screening. Adherence to colonoscopy follow-up after FIT had to be 4%–13% higher than mt-sDNA to reach equivalent LYG. The theoretical S1 favored FIT versus mt-sDNA (LYG 316 vs. 297; colorectal cancer incidence reduction 68% vs. 64%; colorectal cancer mortality reduction 76% vs. 72%). The more realistic S2 and S3 favored mt-sDNA versus FIT (S2: LYG 284 vs. 245, colorectal cancer incidence reduction 61% vs. 50%, colorectal cancer mortality reduction 69% vs. 59%; S3: LYG 203 vs. 113, colorectal cancer incidence reduction 43% vs. 23%, colorectal cancer mortality reduction 49% vs. 27%, respectively). Incorporating realistic adherence rates for colorectal cancer screening influences modeled outcomes and should be considered when assessing comparative effectiveness. Prevention Relevance: Adherence rates for initial colorectal cancer screening by FIT or mt-sDNA and for colonoscopy follow-up of a positive initial test influence the comparative effectiveness of these screening strategies. Using adherence rates based on published data for stool-based testing and colonoscopy follow-up yielded superior outcomes with an mt-sDNA versus FIT-screening strategy.

Abstract Background Real‐world data for patients with positive colorectal cancer (CRC) screening stool‐tests demonstrate that adenoma detection rates are lower when endoscopists are blinded to the stool‐test results. This suggests adenoma sensitivity may be lower for screening colonoscopy than for follow‐up to a known positive stool‐based test. Previous CRC microsimulation models assume identical sensitivities between screening and follow‐up colonoscopies after positive stool‐tests. The Colorectal Cancer and Adenoma Incidence and Mortality Microsimulation Model (CRC‐AIM) was used to explore the impact on screening outcomes when assuming different adenoma sensitivity between screening and combined follow‐up/surveillance colonoscopies. Methods Modeled screening strategies included colonoscopy every 10 years, triennial multitarget stool DNA (mt‐sDNA), or annual fecal immunochemical test (FIT) from 50 to 75 years. Outcomes were reported per 1000 individuals without diagnosed CRC at age 40. Base‐case adenoma sensitivity values were identical for screening and follow‐up/surveillance colonoscopies. Ranges of adenoma sensitivity values for colonoscopy performance were developed using different slopes of odds ratio adjustments and were designated as small, medium, or large impact scenarios. Results As the differences in adenoma sensitivity for screening versus follow‐up/surveillance colonoscopies became greater, life‐years gained (LYG) and reductions in CRC‐related incidence and mortality versus no screening increased for mt‐sDNA and FIT and decreased for screening colonoscopy. The LYG relative to screening colonoscopy reached >90% with FIT in the base‐case scenario and with mt‐sDNA in a “medium impact” scenario. Conclusions Assuming identical adenoma sensitivities for screening and follow‐up/surveillance colonoscopies underestimate the potential benefits of stool‐based screening strategies.