Does a long time to colonoscopy after a positive faecal immunochemical test result have a deleterious impact on colorectal cancer outcomes? A nationwide cohort study

BACKGROUND: Depending on the colorectal cancer (CRC) screening programme, a colonoscopy should be performed within 1-3 months after a positive faecal immunochemical test (FIT) result. However, such short timescales may be difficult to meet and seem trivial when most CRCs take years to develop. OBJECTIVE: To assess the impact of time to colonoscopy on CRC outcomes. DESIGN: This French nationwide retrospective cohort study included individuals with a positive FIT result between 2016 and 2019 and a subsequent colonoscopy performed within 24 months. The risks of CRC, advanced-stage CRC and advanced adenoma (AA) according to time interval to colonoscopy were assessed and evaluated on individual and socio-geographic characteristics. RESULTS: Overall, 374 113 FIT-positive individuals underwent post-FIT colonoscopy (86.6% compliance rate), with 21 616 CRCs and 122 359 AAs diagnosed. Compared with the 2-3 months interval class, no increased risk of CRC, advanced-stage CRC or AA was observed after 3 months up to 24 months, with adjusted odds ratio after 12 months at 0.93 (0.95 CI 0.83 to 1.03), 1.04 (0.85 to 1.25) and 0.88 (0.82 to 0.93), respectively. Individuals with high faecal haemoglobin concentrations (f-Hb ≥200 µg/g) were respectively eight, eleven and two times more likely to have a CRC, an advanced-stage CRC or an AA as compared with the 30-40 µg/g class. CONCLUSION: No increased risk of CRC, advanced-stage CRC or AA was observed up to 24 months. Our findings suggest that ensuring colonoscopy compliance after a positive FIT may take precedence over rigid adherence to interval. The higher the f-Hb, the sooner the colonoscopy should be performed.