Objective: The present study aimed to evaluate the adherence to the colorectal cancer (CRC) screening protocol and determine the predictors during 5 years of follow-up.
Materials and Methods: A retrospective study was conducted in 1,228 Thai participants, aged 50 to 65 years, who joined the CRC screening project. Adherence was defined by receiving of the first screening colonoscopy, annual fecal immunochemical test (FIT) for 5 years and second colonoscopy based on risk groups.
Results: Of the 1,228 participants, 44.5% adhered to the protocol, 45.3% completed annual FIT, and 97.2% completed colonoscopy. Male participants were more likely to adhere to the protocol (OR 1.34, 95% CI 1.04 to 1.71) and annual FIT (OR 1.32, 95% CI 1.03 to 1.69). Participants with adequate vegetable consumption tended to adhere to the protocol (OR 1.49, 95% CI 1.05 to 2.12) and annual FIT (OR 1.52, 95% CI 1.07 to 2.15), and individuals with adequate fruit consumption adhered to the protocol (OR 1.82, 95% CI 1.07 to 3.08) and annual FIT (OR 1.76, 95% CI 1.04 to 2.95). The model of these three predictors demonstrated goodness of fit.
Conclusion: Rates of adherence to CRC screening protocol and annual FIT are less than 50%. Promoting the adherence to CRC screening remains necessary.

Keywords: Adherence, CRC screening, Colorectal cancer, 5-year follow-up