Prioritisation by FIT to mitigate the impact of delays in the two-week wait colorectal cancer referral pathway during the COVID-19 pandemic: a UK modelling study

Objective: To evaluate the impact of faecal immunochemical testing (FIT) prioritisation to mitigate the impact of delay in the 2-week-wait (2WW) colorectal cancer (CRC) urgent diagnostic pathway consequent from the Coronavirus disease 2019 (COVID-19) pandemic. Design: We modelled the reduction in CRC survival and life years lost resultant from per-patient delays of 2-6 months in the 2WW pathway. We stratified by age-group, individual-level benefit in CRC cancer survival versus age-specific nosocomial COVID-19-related fatality per referred patient undergoing colonoscopy. We modelled mitigation strategies using thresholds of FIT triage of 2, 10 and 150 ug Hb/g to prioritise 2WW referrals for colonoscopy. To construct the underlying models, we employed 10-year net CRC survival for England 2008-2017, 2WW pathway CRC case and referral volumes and per-day-delay hazard ratios generated from observational studies of diagnosis-to-treatment interval. Results: Delay of 2/ 4/ 6 months across all 11,266 CRC patients diagnosed per typical year via the 2WW pathway were estimated to result in 653/ 1,419/ 2,250 attributable deaths and loss of 9,214/ 20,315/ 32,799 life years. Risk-benefit from urgent investigatory referral is particularly sensitive to nosocomial COVID-19 infection rates for patients aged >60. Prioritisation out of delay for the 18% of symptomatic referrals with FIT >10 ug Hb/g would avoid 89% of these deaths attributable to delay, whilst reducing immediate requirement for colonoscopy by >80%. Conclusions: Delays in the pathway to CRC diagnosis and treatment have potential to cause significant mortality and loss of life years. FIT-triage of symptomatic patients in primary care could streamline access to colonoscopy, reduce delays for true-positive CRC cases and reduce nosocomial COVID-19 mortality in older true-negative 2WW referrals. However, this strategy offers benefit only in short-term rationalisation of limited endoscopy services: the appreciable false-negative rate in symptomatic patients of FIT means colonoscopy is still required in the majority.