Colorectal Cancer Screening within Colonoscopy Capacity Constraints: Can FIT-Based Programs Save More Lives by Trading off More Sensitive Test Cutoffs against Longer Screening Intervals?

Introduction: Colorectal cancer (CRC) prevention programmes using faecal immunochemical testing (FIT) in screening rely on colonoscopy for secondary and surveillance testing. Colonoscopy capacity is an important constraint. Some European programmes lack sufficient capacity to provide optimal screening intensity regarding age-ranges, intervals and FIT cut-offs. It is currently unclear how to optimise programmes within colonoscopy capacity constraints.
Design: Microsimulation modelling, using the MISCAN-Colon model was used to determine if more effective CRC screening programmes can be identified within constrained colonoscopy capacity. 525 strategies were modelled and compared, varying 3 key screening parameters; screening intervals; age-ranges and FIT cut-offs, including previously unevaluated 4- and 5-year screening intervals (using a lifetime-horizon and 100% adherence). Results were compared with the policy decisions taken in Ireland to provide CRC screening within available colonoscopy capacity. Outcomes estimated net costs, quality-adjusted-life-years and required colonoscopies. The optimal strategies within finite colonoscopy capacity constraints were identified.
Results: Combining a reduced FIT cut-off of 10µg Hb/g, an extended screening interval of 4 years and an age range of 60-72 years requires 6% fewer colonoscopies, reduces net costs by 23% while preventing 15% more CRC deaths and saving 16% more QALYs relative to a strategy (FIT 40µg Hb/g, 2-yearly, 60-70 years) approximating current policy.
Conclusion: Previously overlooked longer screening intervals may optimise cancer prevention with finite colonoscopy capacity constraints. Changes could save lives, reduce costs, and relieve colonoscopy capacity pressures. These findings are relevant to CRC screening programmes across Europe that employ FIT-based testing which face colonoscopy capacity constraints.