Fecal Immunochemical Testing and the Risk of Advanced Colorectal Neoplasia: A Difference-In-Difference Analysis

PURPOSE To evaluate the effectiveness of fecal immunochemical testing (FIT) in colorectal cancer screening. METHODS We conducted a prospective cohort study among 5,598 participants age 40-74 years between 2012 and 2020 in Tianjin, China. Inverse probability weighting was adopted to adjust for potential imbalanced factors between groups. A Cox proportional hazards model was used to estimate the weighted associations between FIT screening and advanced colorectal neoplasia. A difference-in-difference (DID) model was adopted to compare the incidence rates of advanced colorectal neoplasia between groups. RESULTS In DID analysis, the rate of incidence was reduced by 0.34 cases per person-years in the screening group as compared with the historical FIT screening group (rate ratio [RR], 0.08 [95% CI, 0.07 to 0.10]) and by 0.06 cases per person-years in the non-FIT screening group as compared with the historical non-FIT screening group (RR, 0.37 [95% CI, 0.29 to 0.48]; P < .001 for both comparisons), with a relative reduction of 0.28. Similar benefit effect from FIT screening was observed in sex and age subgroups. CONCLUSION FIT screening was associated with a reduction in incidence density from advanced colorectal neoplasia.