Risk-based guidance for choosing FIT or colonoscopy in colorectal cancer screening: a modelling study

In colorectal cancer (CRC) screening settings offering both colonoscopy and fecal immunochemical test (FIT), guidance on who should get colonoscopy could optimize resource use. This study aimed to identify efficient guidance strategies, maximizing quality-adjusted lifeyears (QALYs) gained for given colonoscopy demand. Using the MISCAN-Colon microsimulation model for Switzerland, we evaluated three strategy types: age-based, starting biennial FIT and switching to 10-yearly colonoscopy at a certain age; risk-score-based, where only individuals with high CRC risk scores undergo colonoscopy; FIT-based, switching to colonoscopy after a quantitative FIT result just below the positivity cutoff and, in some strategies, also at a certain age. Reference strategies included (1) colonoscopy-only and (2) equal proportions of individuals choosing FIT or colonoscopy at age 50. Age- and risk-score-based strategies with switches or risk assessments at ages 54, 64 or 74 were efficient. Compared to the reference strategies, QALYs gained could increase by (1) 10.0% or (2) 6.7% without increasing colonoscopy demand. FIT-based switching strategies were not efficient. Therefore, screening programs like those in Switzerland and the US can improve efficiency by guiding individuals towards FIT or colonoscopy simply based on age. More complex approaches using prior FITs or risk scores would not outperform age-based approaches. 199 words.