Abstract
OBJECTIVE: To quantify the associations between time to colonoscopy after a positive fecal immunochemical test (FIT+) and colorectal cancer (CRC)-related outcomes in the context of a provincial, population-based CRC screening program. SETTING: Population-based, retrospective cohort study in Alberta, Canada, including Albertans aged 50-74 with at least one FIT+ in 2014-2017. METHODS: Study outcomes were CRC diagnosis after a FIT+ and a diagnostic follow-up colonoscopy in 2014-2019 and CRC stage at diagnosis. Multivariable logistic regression models were used to evaluate the relative risk of any CRC or advanced-stage CRC. Results were presented as crude odds ratio (OR) and adjusted OR (aOR) with 95% confidence intervals (CIs). RESULTS: Of the 787,967 participants who had a FIT, 63,232 (8%) had a FIT+ and met the study's eligibility criteria. The risk of any CRC or advanced-stage CRC stayed high and was relatively consistent for follow-up colonoscopies performed within 1-12 months of the FIT+. After 12 months, the risk of CRC was considerably higher, particularly for advanced-stage CRC. The OR and aOR for any CRC were 1.40 (95% CI: 1.13-1.73; p < 0.05) and 1.20 (95% CI: 0.96-1.49), respectively, and the OR and aOR for advanced-stage CRC were 1.42 (95% CI: 0.98-2.08) and 0.88 (95% CI: 0.59-1.32), respectively, for colonoscopy follow-up within 12-18 months versus 1-2 months. CONCLUSIONS: For Albertans who used FIT for CRC screening, a longer time interval between a FIT+ and follow-up colonoscopy, particularly over 12 months, increases the risk of having CRC and decreases the effectiveness of CRC screening programs.