Attendance and Diagnostic Yield of Repeated Fecal Immunochemical Test Screening With Intervals of 1, 2, or 3 Years: A Comparative Population-Based Colorectal Cancer Screening Trial

Abstract

Introduction: Fecal immunochemical tests (FIT) have suboptimal sensitivity for advanced neoplasia and require successive screening rounds for an optimal preventive effect. However, data about the influence of screening interval length on attendance and diagnostic yield are lacking, nor is it known whether the increased sensitivity of FIT compared to the conventional guaiac-based FOBT allows for longer screening intervals. We therefore performed repeated FIT screening in a population-based trial comparing 1, 2, and 3 year intervals. Methods: Three representative samples of the Dutch population (total=7,500) aged 50-75 years were randomly selected prior to invitation. Individuals were invited for two 1-sample FIT screening rounds (cut-off ≥ 50 ng Hb/mL) with intervals of respectively 1 (group A), 2 (B), or 3 years (C). Subjects with a positive FIT in the 1st screening round, and those who had moved away/died were not invited for the 2nd round. Results: In group A, attendance was 64.6% (1,544/2,391) in the 1st and 62.7% (n=1,302/2,077) in the 2nd screening round. Of the 1st round participants, 89.8% also attended the 2nd screening round. Of the non-participants in the 1st screening round, 16.3% did participate in the 2nd round. We refer to Table 1 for group B and C. Corrected for 1st round attendance, a longer screening interval improved participation in the 2nd FIT-based screening round (group A (reference) 89.8% vs. group B 90.9%, and vs. group C 91.4%; p<0.05). Attendance of 1st round non-participants was also higher in group B and C compared to the reference group A (respectively 19.3%, and 18.9%, vs 16.3%; p<0.05). The proportion of participants attending at least one screening round did not significantly differ between the screening intervals (group A: 67.4%, group B: 66.1%, group C 67.0%; p=0.60). The overall positivity rate (PR) in the 2nd screening round was significantly lower compared to the 1st (6.0% vs. 8.4%, OR 0.69; CI 0.58-0.82). However, a longer interval was not associated with higher PR at repeated screening (p= 0.36). Similarly, the overall detection rate (DR) of advanced neoplasia was significantly lower in the 2nd round (1.8%, OR 0.55; CI 0.41-0.74) compared to the 1st screening round (3.3%). Colorectal cancers were found in 0.44% of 1st round participants vs. 0.17% in 2nd round participants (OR 0.39; CI 0.16-0.98). The length of screening interval did not affect the DR of advanced neoplasia in the 2nd round (p=0.33). Conclusion: Attendance of repeated FIT screening is moderately high with uptake percentages approximating 70%. A longer screening interval of 2 or 3 years results in significantly higher participation compared to annual screening. In the 2nd screening round, positivity and detection rates were significantly lower than in the 1st screening round. However, both were not affected by the length of the screening interval. Table 1