Benefits, harms and cost-effectiveness of potential age-extensions to the National Bowel Cancer Screening Program in Australia

BACKGROUND: The Australian National Bowel Cancer Screening Program(NBCSP) is rolling out 2-yearly immunochemical Faecal Occult Blood Test screening in people 50-74 years. This study aimed to evaluate the benefits, harms and cost-effectiveness of extending the NBCSP to younger and/or older ages. METHODS: A comprehensive validated microsimulation model, Policy1-Bowel, was used to simulate the fully rolled-out NBCSP and alternative strategies assuming screening starts at 45 or 40 years and/or ceases at 79 or 84 years given three scenarios:(i) perfect adherence(100%), (ii) high adherence(60%), and (ii) low adherence(40%, as currently achieved). RESULTS: The current NBCSP will reduce colorectal cancer incidence(mortality) by 23-51(36-74)% compared to no screening (range reflects participation); extending screening to younger or older ages would result in additional reductions of 2-6(2-9) or 1-3(3-7) percentage points, respectively. With an indicative willingness-to-pay threshold of A$50,000/life-year saved (LYS), only screening from 50-74 (incremental cost-effective ratio [ICER]:A$2,984-5,981/LYS) or from 45-74 (ICER:A$17,053-29,512/LYS) remained cost-effective in all participation scenarios. The number-needed-to-colonoscope to prevent a death over the lifetime of a cohort in the current NBCSP is 35-49. Starting at 45 years would increase colonoscopy demand for program-related colonoscopies by 3-14% and be associated with 55-170 additional colonoscopies per additional death prevented. CONCLUSIONS: Starting screening at 45 years could be cost-effective, but it would increase colonoscopy demand and would be associated with a less favourable incremental benefits-to-harms trade-off than screening from 50-74 years. IMPACT: The study underpins recently updated Australian colorectal cancer management guidelines which recommends that the NBCSP continues to offer bowel screening from 50-74 years